261.
Nias, Isabel J; Cornford, Stephen L; Payne, Antony J
Contrasting the modelled sensitivity of the Amundsen Sea Embayment ice streams Journal Article
In: J. Glaciol., vol. 62, no. 233, pp. 552–562, 2016.
@article{Nias2016-ql,
title = {Contrasting the modelled sensitivity of the Amundsen Sea
Embayment ice streams},
author = {Isabel J Nias and Stephen L Cornford and Antony J Payne},
year = {2016},
date = {2016-06-01},
journal = {J. Glaciol.},
volume = {62},
number = {233},
pages = {552–562},
publisher = {Cambridge University Press (CUP)},
abstract = {AbstractPresent-day mass loss from the West Antarctic ice sheet
is centred on the Amundsen Sea Embayment (ASE), primarily
through ice streams, including Pine Island, Thwaites and Smith
glaciers. To understand the differences in response of these ice
streams, we ran a perturbed parameter ensemble, using a
vertically-integrated ice flow model with adaptive mesh
refinement. We generated 71 sets of three physical parameters
(basal traction coefficient, ice viscosity stiffening factor and
sub-shelf melt rate), which we used to simulate the ASE for 50
years. We also explored the effects of different bed geometries
and basal sliding laws. The mean rate of sea-level rise across
the ensemble of simulations is comparable with current observed
rates for the ASE. We found evidence that grounding line
dynamics are sensitive to features in the bed geometry:
simulations using BedMap2 geometry resulted in a higher rate of
sea-level rise than simulations using a rougher geometry,
created using mass conservation. Modelled grounding-line retreat
of all the three ice streams was sensitive to viscosity and
basal traction, while the melt rate was more important in Pine
Island and Smith glaciers, which flow through more confined ice
shelves than Thwaites, which has a relatively unconfined shelf.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
AbstractPresent-day mass loss from the West Antarctic ice sheet
is centred on the Amundsen Sea Embayment (ASE), primarily
through ice streams, including Pine Island, Thwaites and Smith
glaciers. To understand the differences in response of these ice
streams, we ran a perturbed parameter ensemble, using a
vertically-integrated ice flow model with adaptive mesh
refinement. We generated 71 sets of three physical parameters
(basal traction coefficient, ice viscosity stiffening factor and
sub-shelf melt rate), which we used to simulate the ASE for 50
years. We also explored the effects of different bed geometries
and basal sliding laws. The mean rate of sea-level rise across
the ensemble of simulations is comparable with current observed
rates for the ASE. We found evidence that grounding line
dynamics are sensitive to features in the bed geometry:
simulations using BedMap2 geometry resulted in a higher rate of
sea-level rise than simulations using a rougher geometry,
created using mass conservation. Modelled grounding-line retreat
of all the three ice streams was sensitive to viscosity and
basal traction, while the melt rate was more important in Pine
Island and Smith glaciers, which flow through more confined ice
shelves than Thwaites, which has a relatively unconfined shelf.
is centred on the Amundsen Sea Embayment (ASE), primarily
through ice streams, including Pine Island, Thwaites and Smith
glaciers. To understand the differences in response of these ice
streams, we ran a perturbed parameter ensemble, using a
vertically-integrated ice flow model with adaptive mesh
refinement. We generated 71 sets of three physical parameters
(basal traction coefficient, ice viscosity stiffening factor and
sub-shelf melt rate), which we used to simulate the ASE for 50
years. We also explored the effects of different bed geometries
and basal sliding laws. The mean rate of sea-level rise across
the ensemble of simulations is comparable with current observed
rates for the ASE. We found evidence that grounding line
dynamics are sensitive to features in the bed geometry:
simulations using BedMap2 geometry resulted in a higher rate of
sea-level rise than simulations using a rougher geometry,
created using mass conservation. Modelled grounding-line retreat
of all the three ice streams was sensitive to viscosity and
basal traction, while the melt rate was more important in Pine
Island and Smith glaciers, which flow through more confined ice
shelves than Thwaites, which has a relatively unconfined shelf.
262.
Stroeve, Julienne C; Crawford, Alex D; Stammerjohn, Sharon
Using timing of ice retreat to predict timing of fall freeze‐up in the Arctic Journal Article
In: Geophys. Res. Lett., vol. 43, no. 12, pp. 6332–6340, 2016.
@article{Stroeve2016-wt,
title = {Using timing of ice retreat to predict timing of fall freeze‐up
in the Arctic},
author = {Julienne C Stroeve and Alex D Crawford and Sharon Stammerjohn},
year = {2016},
date = {2016-06-01},
journal = {Geophys. Res. Lett.},
volume = {43},
number = {12},
pages = {6332–6340},
publisher = {American Geophysical Union (AGU)},
abstract = {AbstractReliable forecasts of the timing of sea ice advance are
needed in order to reduce risks associated with operating in the
Arctic as well as planning of human and environmental
emergencies. This study investigates the use of a simple
statistical model relating the timing of ice retreat to the
timing of ice advance, taking advantage of the inherent
predictive power supplied by the seasonal ice‐albedo feedback
and ocean heat uptake. Results show that using the last retreat
date to predict the first advance date is applicable in some
regions, such as Baffin Bay and the Laptev and East Siberian
seas, where a predictive skill is found even after accounting
for the long‐term trend in both variables. Elsewhere, in the
Arctic, there is some predictive skills depending on the year
(e.g., Kara and Beaufort seas), but none in regions such as the
Barents and Bering seas or the Sea of Okhotsk. While there is
some suggestion that the relationship is strengthening over
time, this may reflect that higher correlations are expected
during periods when the underlying trend is strong.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
AbstractReliable forecasts of the timing of sea ice advance are
needed in order to reduce risks associated with operating in the
Arctic as well as planning of human and environmental
emergencies. This study investigates the use of a simple
statistical model relating the timing of ice retreat to the
timing of ice advance, taking advantage of the inherent
predictive power supplied by the seasonal ice‐albedo feedback
and ocean heat uptake. Results show that using the last retreat
date to predict the first advance date is applicable in some
regions, such as Baffin Bay and the Laptev and East Siberian
seas, where a predictive skill is found even after accounting
for the long‐term trend in both variables. Elsewhere, in the
Arctic, there is some predictive skills depending on the year
(e.g., Kara and Beaufort seas), but none in regions such as the
Barents and Bering seas or the Sea of Okhotsk. While there is
some suggestion that the relationship is strengthening over
time, this may reflect that higher correlations are expected
during periods when the underlying trend is strong.
needed in order to reduce risks associated with operating in the
Arctic as well as planning of human and environmental
emergencies. This study investigates the use of a simple
statistical model relating the timing of ice retreat to the
timing of ice advance, taking advantage of the inherent
predictive power supplied by the seasonal ice‐albedo feedback
and ocean heat uptake. Results show that using the last retreat
date to predict the first advance date is applicable in some
regions, such as Baffin Bay and the Laptev and East Siberian
seas, where a predictive skill is found even after accounting
for the long‐term trend in both variables. Elsewhere, in the
Arctic, there is some predictive skills depending on the year
(e.g., Kara and Beaufort seas), but none in regions such as the
Barents and Bering seas or the Sea of Okhotsk. While there is
some suggestion that the relationship is strengthening over
time, this may reflect that higher correlations are expected
during periods when the underlying trend is strong.
263.
Tedesco, M; Mote, T; Fettweis, X; Hanna, E; Jeyaratnam, J; Booth, J F; Datta, R; Briggs, K
Arctic cut-off high drives the poleward shift of a new Greenland melting record Journal Article
In: Nat. Commun., vol. 7, no. 1, pp. 11723, 2016.
@article{Tedesco2016-ao,
title = {Arctic cut-off high drives the poleward shift of a new Greenland
melting record},
author = {M Tedesco and T Mote and X Fettweis and E Hanna and J Jeyaratnam and J F Booth and R Datta and K Briggs},
year = {2016},
date = {2016-06-01},
journal = {Nat. Commun.},
volume = {7},
number = {1},
pages = {11723},
publisher = {Springer Science and Business Media LLC},
abstract = {AbstractLarge-scale atmospheric circulation controls the mass
and energy balance of the Greenland ice sheet through its impact
on radiative budget, runoff and accumulation. Here, using
reanalysis data and the outputs of a regional climate model, we
show that the persistence of an exceptional atmospheric ridge,
centred over the Arctic Ocean, was responsible for a poleward
shift of runoff, albedo and surface temperature records over the
Greenland during the summer of 2015. New records of monthly mean
zonal winds at 500 hPa and of the maximum latitude of ridge
peaks of the 5,700$±$50 m isohypse over the Arctic were
associated with the formation and persistency of a cutoff high.
The unprecedented (1948–2015) and sustained atmospheric
conditions promoted enhanced runoff, increased the surface
temperatures and decreased the albedo in northern Greenland,
while inhibiting melting in the south, where new melting records
were set over the past decade.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
AbstractLarge-scale atmospheric circulation controls the mass
and energy balance of the Greenland ice sheet through its impact
on radiative budget, runoff and accumulation. Here, using
reanalysis data and the outputs of a regional climate model, we
show that the persistence of an exceptional atmospheric ridge,
centred over the Arctic Ocean, was responsible for a poleward
shift of runoff, albedo and surface temperature records over the
Greenland during the summer of 2015. New records of monthly mean
zonal winds at 500 hPa and of the maximum latitude of ridge
peaks of the 5,700$±$50 m isohypse over the Arctic were
associated with the formation and persistency of a cutoff high.
The unprecedented (1948–2015) and sustained atmospheric
conditions promoted enhanced runoff, increased the surface
temperatures and decreased the albedo in northern Greenland,
while inhibiting melting in the south, where new melting records
were set over the past decade.
and energy balance of the Greenland ice sheet through its impact
on radiative budget, runoff and accumulation. Here, using
reanalysis data and the outputs of a regional climate model, we
show that the persistence of an exceptional atmospheric ridge,
centred over the Arctic Ocean, was responsible for a poleward
shift of runoff, albedo and surface temperature records over the
Greenland during the summer of 2015. New records of monthly mean
zonal winds at 500 hPa and of the maximum latitude of ridge
peaks of the 5,700$±$50 m isohypse over the Arctic were
associated with the formation and persistency of a cutoff high.
The unprecedented (1948–2015) and sustained atmospheric
conditions promoted enhanced runoff, increased the surface
temperatures and decreased the albedo in northern Greenland,
while inhibiting melting in the south, where new melting records
were set over the past decade.
264.
Mioduszewski, J R; Rennermalm, A K; Hammann, A; Tedesco, M; Noble, E U; Stroeve, J C; Mote, T L
Atmospheric drivers of Greenland surface melt revealed by self‐organizing maps Journal Article
In: J. Geophys. Res., vol. 121, no. 10, pp. 5095–5114, 2016.
@article{Mioduszewski2016-bp,
title = {Atmospheric drivers of Greenland surface melt revealed by
self‐organizing maps},
author = {J R Mioduszewski and A K Rennermalm and A Hammann and M Tedesco and E U Noble and J C Stroeve and T L Mote},
year = {2016},
date = {2016-05-01},
journal = {J. Geophys. Res.},
volume = {121},
number = {10},
pages = {5095–5114},
publisher = {American Geophysical Union (AGU)},
abstract = {AbstractRecent acceleration in surface melt on the Greenland ice
sheet (GrIS) has occurred concurrently with a rapidly warming
Arctic and has been connected to persistent, anomalous
atmospheric circulation patterns over Greenland. To identify
synoptic setups favoring enhanced GrIS surface melt and their
decadal changes, we develop a summer Arctic synoptic climatology
by employing self‐organizing maps. These are applied to daily
500 hPa geopotential height fields obtained from the Modern Era
Retrospective Analysis for Research and Applications reanalysis,
1979–2014. Particular circulation regimes are related to
meteorological conditions and GrIS surface melt estimated with
outputs from the Modèle Atmosphérique Régional. Our
results demonstrate that the largest positive melt anomalies
occur in concert with positive height anomalies near Greenland
associated with wind, temperature, and humidity patterns
indicative of strong meridional transport of heat and moisture.
We find an increased frequency in a 500 hPa ridge over Greenland
coinciding with a 63% increase in GrIS melt between the
1979–1988 and 2005–2014 periods, with 75.0% of surface melt
changes attributed to thermodynamics, 17% to dynamics, and
8.0% to a combination. We also confirm that the 2007–2012 time
period has the largest dynamic forcing relative of any period
but also demonstrate that increased surface energy fluxes,
temperature, and moisture separate from dynamic changes
contributed more to melt even during this period. This implies
that GrIS surface melt is likely to continue to increase in
response to an ever warmer future Arctic, regardless of future
atmospheric circulation patterns.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
AbstractRecent acceleration in surface melt on the Greenland ice
sheet (GrIS) has occurred concurrently with a rapidly warming
Arctic and has been connected to persistent, anomalous
atmospheric circulation patterns over Greenland. To identify
synoptic setups favoring enhanced GrIS surface melt and their
decadal changes, we develop a summer Arctic synoptic climatology
by employing self‐organizing maps. These are applied to daily
500 hPa geopotential height fields obtained from the Modern Era
Retrospective Analysis for Research and Applications reanalysis,
1979–2014. Particular circulation regimes are related to
meteorological conditions and GrIS surface melt estimated with
outputs from the Modèle Atmosphérique Régional. Our
results demonstrate that the largest positive melt anomalies
occur in concert with positive height anomalies near Greenland
associated with wind, temperature, and humidity patterns
indicative of strong meridional transport of heat and moisture.
We find an increased frequency in a 500 hPa ridge over Greenland
coinciding with a 63% increase in GrIS melt between the
1979–1988 and 2005–2014 periods, with 75.0% of surface melt
changes attributed to thermodynamics, 17% to dynamics, and
8.0% to a combination. We also confirm that the 2007–2012 time
period has the largest dynamic forcing relative of any period
but also demonstrate that increased surface energy fluxes,
temperature, and moisture separate from dynamic changes
contributed more to melt even during this period. This implies
that GrIS surface melt is likely to continue to increase in
response to an ever warmer future Arctic, regardless of future
atmospheric circulation patterns.
sheet (GrIS) has occurred concurrently with a rapidly warming
Arctic and has been connected to persistent, anomalous
atmospheric circulation patterns over Greenland. To identify
synoptic setups favoring enhanced GrIS surface melt and their
decadal changes, we develop a summer Arctic synoptic climatology
by employing self‐organizing maps. These are applied to daily
500 hPa geopotential height fields obtained from the Modern Era
Retrospective Analysis for Research and Applications reanalysis,
1979–2014. Particular circulation regimes are related to
meteorological conditions and GrIS surface melt estimated with
outputs from the Modèle Atmosphérique Régional. Our
results demonstrate that the largest positive melt anomalies
occur in concert with positive height anomalies near Greenland
associated with wind, temperature, and humidity patterns
indicative of strong meridional transport of heat and moisture.
We find an increased frequency in a 500 hPa ridge over Greenland
coinciding with a 63% increase in GrIS melt between the
1979–1988 and 2005–2014 periods, with 75.0% of surface melt
changes attributed to thermodynamics, 17% to dynamics, and
8.0% to a combination. We also confirm that the 2007–2012 time
period has the largest dynamic forcing relative of any period
but also demonstrate that increased surface energy fluxes,
temperature, and moisture separate from dynamic changes
contributed more to melt even during this period. This implies
that GrIS surface melt is likely to continue to increase in
response to an ever warmer future Arctic, regardless of future
atmospheric circulation patterns.
265.
Petty, Alek; Tsamados, Michel; Kurtz, Nathan; Farrell, Sinead; Newman, Thomas; Harbeck, Jeremy; Feltham, Daniel; Richter-Menge, Jackie
Characterizing Arctic sea ice topography using high-resolution IceBridge data Journal Article
In: Cryosphere, vol. 10, no. 3, pp. 1161–1179, 2016.
@article{Petty2016-fl,
title = {Characterizing Arctic sea ice topography using high-resolution
IceBridge data},
author = {Alek Petty and Michel Tsamados and Nathan Kurtz and Sinead Farrell and Thomas Newman and Jeremy Harbeck and Daniel Feltham and Jackie Richter-Menge},
year = {2016},
date = {2016-05-01},
journal = {Cryosphere},
volume = {10},
number = {3},
pages = {1161–1179},
publisher = {Copernicus GmbH},
abstract = {We present an analysis of Arctic sea ice topography using high
resolution, three-dimensional, surface elevation data from the
Airborne Topographic Mapper, flown as part of NASA's Operation
IceBridge mission. Surface features in the sea ice cover are
detected using a newly developed surface feature picking
algorithm. We derive information regarding the height, volume
and geometry of surface features from 2009-2014 within the
Beaufort/Chukchi and Central Arctic regions. The results are
delineated by ice type to estimate the topographic variability
across first-year and multi-year ice regimes. The results
demonstrate that Arctic sea ice topography exhibits significant
spatial variability, mainly driven by the increased surface
feature height and volume (per unit area) of the multi-year ice
that dominates the Central Arctic region. The multi-year ice
topography exhibits greater interannual variability compared to
the first-year ice regimes, which dominates the total ice
topography variability across both regions. The ice topography
also shows a clear coastal dependency, with the feature height
and volume increasing as a function of proximity to the nearest
coastline, especially north of Greenland and the Canadian
Archipelago. A strong correlation between ice topography and ice
thickness (from the IceBridge sea ice product) is found, using a
square-root relationship. The results allude to the importance
of ice deformation variability in the total sea ice mass
balance, and provide crucial information regarding the tail of
the ice thickness distribution across the western Arctic. Future
research priorities associated with this new dataset are
presented and discussed, especially in relation to calculations
of atmospheric form drag.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We present an analysis of Arctic sea ice topography using high
resolution, three-dimensional, surface elevation data from the
Airborne Topographic Mapper, flown as part of NASA's Operation
IceBridge mission. Surface features in the sea ice cover are
detected using a newly developed surface feature picking
algorithm. We derive information regarding the height, volume
and geometry of surface features from 2009-2014 within the
Beaufort/Chukchi and Central Arctic regions. The results are
delineated by ice type to estimate the topographic variability
across first-year and multi-year ice regimes. The results
demonstrate that Arctic sea ice topography exhibits significant
spatial variability, mainly driven by the increased surface
feature height and volume (per unit area) of the multi-year ice
that dominates the Central Arctic region. The multi-year ice
topography exhibits greater interannual variability compared to
the first-year ice regimes, which dominates the total ice
topography variability across both regions. The ice topography
also shows a clear coastal dependency, with the feature height
and volume increasing as a function of proximity to the nearest
coastline, especially north of Greenland and the Canadian
Archipelago. A strong correlation between ice topography and ice
thickness (from the IceBridge sea ice product) is found, using a
square-root relationship. The results allude to the importance
of ice deformation variability in the total sea ice mass
balance, and provide crucial information regarding the tail of
the ice thickness distribution across the western Arctic. Future
research priorities associated with this new dataset are
presented and discussed, especially in relation to calculations
of atmospheric form drag.
resolution, three-dimensional, surface elevation data from the
Airborne Topographic Mapper, flown as part of NASA's Operation
IceBridge mission. Surface features in the sea ice cover are
detected using a newly developed surface feature picking
algorithm. We derive information regarding the height, volume
and geometry of surface features from 2009-2014 within the
Beaufort/Chukchi and Central Arctic regions. The results are
delineated by ice type to estimate the topographic variability
across first-year and multi-year ice regimes. The results
demonstrate that Arctic sea ice topography exhibits significant
spatial variability, mainly driven by the increased surface
feature height and volume (per unit area) of the multi-year ice
that dominates the Central Arctic region. The multi-year ice
topography exhibits greater interannual variability compared to
the first-year ice regimes, which dominates the total ice
topography variability across both regions. The ice topography
also shows a clear coastal dependency, with the feature height
and volume increasing as a function of proximity to the nearest
coastline, especially north of Greenland and the Canadian
Archipelago. A strong correlation between ice topography and ice
thickness (from the IceBridge sea ice product) is found, using a
square-root relationship. The results allude to the importance
of ice deformation variability in the total sea ice mass
balance, and provide crucial information regarding the tail of
the ice thickness distribution across the western Arctic. Future
research priorities associated with this new dataset are
presented and discussed, especially in relation to calculations
of atmospheric form drag.
266.
Li, Yun; Ji, Rubao; Jenouvrier, Stephanie; Jin, Meibing; Stroeve, Julienne
Synchronicity between ice retreat and phytoplankton bloom in circum‐Antarctic polynyas Journal Article
In: Geophys. Res. Lett., vol. 43, no. 5, pp. 2086–2093, 2016.
@article{Li2016-ba,
title = {Synchronicity between ice retreat and phytoplankton bloom in
circum‐Antarctic polynyas},
author = {Yun Li and Rubao Ji and Stephanie Jenouvrier and Meibing Jin and Julienne Stroeve},
year = {2016},
date = {2016-03-01},
journal = {Geophys. Res. Lett.},
volume = {43},
number = {5},
pages = {2086–2093},
publisher = {American Geophysical Union (AGU)},
abstract = {AbstractPhytoplankton in Antarctic coastal polynyas has a
temporally short yet spatially variant growth window constrained
by ice cover and day length. Using 18‐year satellite
measurements (1997–2015) of sea ice and chlorophyll
concentrations, we assessed the synchronicity between the spring
phytoplankton bloom and light availability, taking into account
the ice cover and the incident solar irradiance, for 50
circum‐Antarctic coastal polynyas. The synchronicity was strong
(i.e., earlier ice‐adjusted light onset leads to earlier bloom
and vice versa) in most of the western Antarctic polynyas but
weak in a majority of the eastern Antarctic polynyas. The
west‐east asymmetry is related to sea ice production rate: the
formation of many eastern Antarctic polynyas is associated with
strong katabatic wind and high sea ice production rate, leading
to stronger water column mixing that could damp phytoplankton
blooms and weaken the synchronicity.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
AbstractPhytoplankton in Antarctic coastal polynyas has a
temporally short yet spatially variant growth window constrained
by ice cover and day length. Using 18‐year satellite
measurements (1997–2015) of sea ice and chlorophyll
concentrations, we assessed the synchronicity between the spring
phytoplankton bloom and light availability, taking into account
the ice cover and the incident solar irradiance, for 50
circum‐Antarctic coastal polynyas. The synchronicity was strong
(i.e., earlier ice‐adjusted light onset leads to earlier bloom
and vice versa) in most of the western Antarctic polynyas but
weak in a majority of the eastern Antarctic polynyas. The
west‐east asymmetry is related to sea ice production rate: the
formation of many eastern Antarctic polynyas is associated with
strong katabatic wind and high sea ice production rate, leading
to stronger water column mixing that could damp phytoplankton
blooms and weaken the synchronicity.
temporally short yet spatially variant growth window constrained
by ice cover and day length. Using 18‐year satellite
measurements (1997–2015) of sea ice and chlorophyll
concentrations, we assessed the synchronicity between the spring
phytoplankton bloom and light availability, taking into account
the ice cover and the incident solar irradiance, for 50
circum‐Antarctic coastal polynyas. The synchronicity was strong
(i.e., earlier ice‐adjusted light onset leads to earlier bloom
and vice versa) in most of the western Antarctic polynyas but
weak in a majority of the eastern Antarctic polynyas. The
west‐east asymmetry is related to sea ice production rate: the
formation of many eastern Antarctic polynyas is associated with
strong katabatic wind and high sea ice production rate, leading
to stronger water column mixing that could damp phytoplankton
blooms and weaken the synchronicity.
267.
Martin, Torge; Tsamados, Michel; Schroeder, David; Feltham, Daniel L
The impact of variable sea ice roughness on changes in Arctic Ocean surface stress: A model study Journal Article
In: J. Geophys. Res. Oceans, vol. 121, no. 3, pp. 1931–1952, 2016.
@article{Martin2016-jz,
title = {The impact of variable sea ice roughness on changes in Arctic
Ocean surface stress: A model study},
author = {Torge Martin and Michel Tsamados and David Schroeder and Daniel L Feltham},
year = {2016},
date = {2016-03-01},
journal = {J. Geophys. Res. Oceans},
volume = {121},
number = {3},
pages = {1931–1952},
publisher = {American Geophysical Union (AGU)},
abstract = {AbstractThe Arctic sea ice cover is thinning and retreating,
causing changes in surface roughness that in turn modify the
momentum flux from the atmosphere through the ice into the
ocean. New model simulations comprising variable sea ice drag
coefficients for both the air and water interface demonstrate
that the heterogeneity in sea ice surface roughness
significantly impacts the spatial distribution and trends of
ocean surface stress during the last decades. Simulations with
constant sea ice drag coefficients as used in most climate
models show an increase in annual mean ocean surface stress
(0.003 N/m2 per decade, 4.6%) due to the reduction of ice
thickness leading to a weakening of the ice and accelerated ice
drift. In contrast, with variable drag coefficients our
simulations show annual mean ocean surface stress is declining
at a rate of −0.002 N/m2 per decade (3.1%) over the period
1980–2013 because of a significant reduction in surface
roughness associated with an increasingly thinner and younger
sea ice cover. The effectiveness of sea ice in transferring
momentum does not only depend on its resistive strength against
the wind forcing but is also set by its top and bottom surface
roughness varying with ice types and ice conditions. This
reveals the need to account for sea ice surface roughness
variations in climate simulations in order to correctly
represent the implications of sea ice loss under global warming.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
AbstractThe Arctic sea ice cover is thinning and retreating,
causing changes in surface roughness that in turn modify the
momentum flux from the atmosphere through the ice into the
ocean. New model simulations comprising variable sea ice drag
coefficients for both the air and water interface demonstrate
that the heterogeneity in sea ice surface roughness
significantly impacts the spatial distribution and trends of
ocean surface stress during the last decades. Simulations with
constant sea ice drag coefficients as used in most climate
models show an increase in annual mean ocean surface stress
(0.003 N/m2 per decade, 4.6%) due to the reduction of ice
thickness leading to a weakening of the ice and accelerated ice
drift. In contrast, with variable drag coefficients our
simulations show annual mean ocean surface stress is declining
at a rate of −0.002 N/m2 per decade (3.1%) over the period
1980–2013 because of a significant reduction in surface
roughness associated with an increasingly thinner and younger
sea ice cover. The effectiveness of sea ice in transferring
momentum does not only depend on its resistive strength against
the wind forcing but is also set by its top and bottom surface
roughness varying with ice types and ice conditions. This
reveals the need to account for sea ice surface roughness
variations in climate simulations in order to correctly
represent the implications of sea ice loss under global warming.
causing changes in surface roughness that in turn modify the
momentum flux from the atmosphere through the ice into the
ocean. New model simulations comprising variable sea ice drag
coefficients for both the air and water interface demonstrate
that the heterogeneity in sea ice surface roughness
significantly impacts the spatial distribution and trends of
ocean surface stress during the last decades. Simulations with
constant sea ice drag coefficients as used in most climate
models show an increase in annual mean ocean surface stress
(0.003 N/m2 per decade, 4.6%) due to the reduction of ice
thickness leading to a weakening of the ice and accelerated ice
drift. In contrast, with variable drag coefficients our
simulations show annual mean ocean surface stress is declining
at a rate of −0.002 N/m2 per decade (3.1%) over the period
1980–2013 because of a significant reduction in surface
roughness associated with an increasingly thinner and younger
sea ice cover. The effectiveness of sea ice in transferring
momentum does not only depend on its resistive strength against
the wind forcing but is also set by its top and bottom surface
roughness varying with ice types and ice conditions. This
reveals the need to account for sea ice surface roughness
variations in climate simulations in order to correctly
represent the implications of sea ice loss under global warming.
268.
Bensassi, Sami; Stroeve, Julienne C; Martínez-Zarzoso, Inmaculada; Barrett, Andrew P
Melting ice, growing trade? Journal Article
In: Elementa (Wash., DC), vol. 4, pp. 000107, 2016.
@article{Bensassi2016-wq,
title = {Melting ice, growing trade?},
author = {Sami Bensassi and Julienne C Stroeve and Inmaculada Martínez-Zarzoso and Andrew P Barrett},
year = {2016},
date = {2016-01-01},
journal = {Elementa (Wash., DC)},
volume = {4},
pages = {000107},
publisher = {University of California Press},
abstract = {Abstract Large reductions in Arctic sea ice, most notably in
summer, coupled with growing interest in Arctic shipping and
resource exploitation have renewed interest in the economic
potential of the Northern Sea Route (NSR). Two key constraints
on the future viability of the NSR pertain to bathymetry and the
future evolution of the sea ice cover. Climate model projections
of future sea ice conditions throughout the rest of the century
suggest that even under the most ``aggressive'' emission
scenario, increases in international trade between Europe and
Asia will be very low. The large inter-annual variability of
weather and sea ice conditions in the route, the Russian toll
imposed for transiting the NSR, together with high insurance
costs and scarce loading/unloading opportunities, limit the use
of the NSR. We show that even if these obstacles are removed,
the duration of the opening of the NSR over the course of the
century is not long enough to offer a consequent boost to
international trade at the macroeconomic level.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract Large reductions in Arctic sea ice, most notably in
summer, coupled with growing interest in Arctic shipping and
resource exploitation have renewed interest in the economic
potential of the Northern Sea Route (NSR). Two key constraints
on the future viability of the NSR pertain to bathymetry and the
future evolution of the sea ice cover. Climate model projections
of future sea ice conditions throughout the rest of the century
suggest that even under the most ``aggressive'' emission
scenario, increases in international trade between Europe and
Asia will be very low. The large inter-annual variability of
weather and sea ice conditions in the route, the Russian toll
imposed for transiting the NSR, together with high insurance
costs and scarce loading/unloading opportunities, limit the use
of the NSR. We show that even if these obstacles are removed,
the duration of the opening of the NSR over the course of the
century is not long enough to offer a consequent boost to
international trade at the macroeconomic level.
summer, coupled with growing interest in Arctic shipping and
resource exploitation have renewed interest in the economic
potential of the Northern Sea Route (NSR). Two key constraints
on the future viability of the NSR pertain to bathymetry and the
future evolution of the sea ice cover. Climate model projections
of future sea ice conditions throughout the rest of the century
suggest that even under the most ``aggressive'' emission
scenario, increases in international trade between Europe and
Asia will be very low. The large inter-annual variability of
weather and sea ice conditions in the route, the Russian toll
imposed for transiting the NSR, together with high insurance
costs and scarce loading/unloading opportunities, limit the use
of the NSR. We show that even if these obstacles are removed,
the duration of the opening of the NSR over the course of the
century is not long enough to offer a consequent boost to
international trade at the macroeconomic level.
269.
Zalasiewicz, Jan; Williams, Mark
Climate change through earth's history Book Section
In: Climate Change, pp. 3–17, Elsevier, 2016.
BibTeX | Tags:
@incollection{Zalasiewicz2016-li,
title = {Climate change through earth's history},
author = {Jan Zalasiewicz and Mark Williams},
year = {2016},
date = {2016-01-01},
booktitle = {Climate Change},
pages = {3–17},
publisher = {Elsevier},
keywords = {},
pubstate = {published},
tppubtype = {incollection}
}
270.
Clark, Peter U; Church, John A; Gregory, Jonathan M; Payne, Anthony J
Recent progress in understanding and projecting regional and global mean sea level change Journal Article
In: Curr. Clim. Change Rep., vol. 1, no. 4, pp. 224–246, 2015.
BibTeX | Tags:
@article{Clark2015-vd,
title = {Recent progress in understanding and projecting regional and
global mean sea level change},
author = {Peter U Clark and John A Church and Jonathan M Gregory and Anthony J Payne},
year = {2015},
date = {2015-12-01},
journal = {Curr. Clim. Change Rep.},
volume = {1},
number = {4},
pages = {224–246},
publisher = {Springer Science and Business Media LLC},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
271.
Ritz, Catherine; Edwards, Tamsin L; Durand, Gaël; Payne, Antony J; Peyaud, Vincent; Hindmarsh, Richard C A
Potential sea-level rise from Antarctic ice-sheet instability constrained by observations Journal Article
In: Nature, vol. 528, no. 7580, pp. 115–118, 2015.
@article{Ritz2015-jy,
title = {Potential sea-level rise from Antarctic ice-sheet instability
constrained by observations},
author = {Catherine Ritz and Tamsin L Edwards and Gaël Durand and Antony J Payne and Vincent Peyaud and Richard C A Hindmarsh},
year = {2015},
date = {2015-12-01},
journal = {Nature},
volume = {528},
number = {7580},
pages = {115–118},
publisher = {Springer Science and Business Media LLC},
abstract = {Large parts of the Antarctic ice sheet lying on bedrock below
sea level may be vulnerable to marine-ice-sheet instability
(MISI), a self-sustaining retreat of the grounding line
triggered by oceanic or atmospheric changes. There is growing
evidence that MISI may be underway throughout the Amundsen Sea
embayment (ASE), which contains ice equivalent to more than a
metre of global sea-level rise. If triggered in other regions,
the centennial to millennial contribution could be several
metres. Physically plausible projections are challenging:
numerical models with sufficient spatial resolution to simulate
grounding-line processes have been too computationally expensive
to generate large ensembles for uncertainty assessment, and
lower-resolution model projections rely on parameterizations
that are only loosely constrained by present day changes. Here
we project that the Antarctic ice sheet will contribute up to 30
cm sea-level equivalent by 2100 and 72 cm by 2200 (95%
quantiles) where the ASE dominates. Our process-based,
statistical approach gives skewed and complex probability
distributions (single mode, 10 cm, at 2100; two modes, 49 cm and
6 cm, at 2200). The dependence of sliding on basal friction is a
key unknown: nonlinear relationships favour higher
contributions. Results are conditional on assessments of MISI
risk on the basis of projected triggers under the climate
scenario A1B (ref. 9), although sensitivity to these is limited
by theoretical and topographical constraints on the rate and
extent of ice loss. We find that contributions are restricted by
a combination of these constraints, calibration with success in
simulating observed ASE losses, and low assessed risk in some
basins. Our assessment suggests that upper-bound estimates from
low-resolution models and physical arguments (up to a metre by
2100 and around one and a half by 2200) are implausible under
current understanding of physical mechanisms and potential
triggers.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Large parts of the Antarctic ice sheet lying on bedrock below
sea level may be vulnerable to marine-ice-sheet instability
(MISI), a self-sustaining retreat of the grounding line
triggered by oceanic or atmospheric changes. There is growing
evidence that MISI may be underway throughout the Amundsen Sea
embayment (ASE), which contains ice equivalent to more than a
metre of global sea-level rise. If triggered in other regions,
the centennial to millennial contribution could be several
metres. Physically plausible projections are challenging:
numerical models with sufficient spatial resolution to simulate
grounding-line processes have been too computationally expensive
to generate large ensembles for uncertainty assessment, and
lower-resolution model projections rely on parameterizations
that are only loosely constrained by present day changes. Here
we project that the Antarctic ice sheet will contribute up to 30
cm sea-level equivalent by 2100 and 72 cm by 2200 (95%
quantiles) where the ASE dominates. Our process-based,
statistical approach gives skewed and complex probability
distributions (single mode, 10 cm, at 2100; two modes, 49 cm and
6 cm, at 2200). The dependence of sliding on basal friction is a
key unknown: nonlinear relationships favour higher
contributions. Results are conditional on assessments of MISI
risk on the basis of projected triggers under the climate
scenario A1B (ref. 9), although sensitivity to these is limited
by theoretical and topographical constraints on the rate and
extent of ice loss. We find that contributions are restricted by
a combination of these constraints, calibration with success in
simulating observed ASE losses, and low assessed risk in some
basins. Our assessment suggests that upper-bound estimates from
low-resolution models and physical arguments (up to a metre by
2100 and around one and a half by 2200) are implausible under
current understanding of physical mechanisms and potential
triggers.
sea level may be vulnerable to marine-ice-sheet instability
(MISI), a self-sustaining retreat of the grounding line
triggered by oceanic or atmospheric changes. There is growing
evidence that MISI may be underway throughout the Amundsen Sea
embayment (ASE), which contains ice equivalent to more than a
metre of global sea-level rise. If triggered in other regions,
the centennial to millennial contribution could be several
metres. Physically plausible projections are challenging:
numerical models with sufficient spatial resolution to simulate
grounding-line processes have been too computationally expensive
to generate large ensembles for uncertainty assessment, and
lower-resolution model projections rely on parameterizations
that are only loosely constrained by present day changes. Here
we project that the Antarctic ice sheet will contribute up to 30
cm sea-level equivalent by 2100 and 72 cm by 2200 (95%
quantiles) where the ASE dominates. Our process-based,
statistical approach gives skewed and complex probability
distributions (single mode, 10 cm, at 2100; two modes, 49 cm and
6 cm, at 2200). The dependence of sliding on basal friction is a
key unknown: nonlinear relationships favour higher
contributions. Results are conditional on assessments of MISI
risk on the basis of projected triggers under the climate
scenario A1B (ref. 9), although sensitivity to these is limited
by theoretical and topographical constraints on the rate and
extent of ice loss. We find that contributions are restricted by
a combination of these constraints, calibration with success in
simulating observed ASE losses, and low assessed risk in some
basins. Our assessment suggests that upper-bound estimates from
low-resolution models and physical arguments (up to a metre by
2100 and around one and a half by 2200) are implausible under
current understanding of physical mechanisms and potential
triggers.
272.
Ritz, Catherine; Edwards, Tamsin L; Durand, Gaël; Payne, Antony J; Peyaud, Vincent; Hindmarsh, Richard C A
Potential sea-level rise from Antarctic ice-sheet instability constrained by observations Journal Article
In: Nature, vol. 528, no. 7580, pp. 115–118, 2015.
@article{Ritz2015-ar,
title = {Potential sea-level rise from Antarctic ice-sheet instability
constrained by observations},
author = {Catherine Ritz and Tamsin L Edwards and Gaël Durand and Antony J Payne and Vincent Peyaud and Richard C A Hindmarsh},
year = {2015},
date = {2015-12-01},
journal = {Nature},
volume = {528},
number = {7580},
pages = {115–118},
publisher = {Springer Science and Business Media LLC},
abstract = {Large parts of the Antarctic ice sheet lying on bedrock below
sea level may be vulnerable to marine-ice-sheet instability
(MISI), a self-sustaining retreat of the grounding line
triggered by oceanic or atmospheric changes. There is growing
evidence that MISI may be underway throughout the Amundsen Sea
embayment (ASE), which contains ice equivalent to more than a
metre of global sea-level rise. If triggered in other regions,
the centennial to millennial contribution could be several
metres. Physically plausible projections are challenging:
numerical models with sufficient spatial resolution to simulate
grounding-line processes have been too computationally expensive
to generate large ensembles for uncertainty assessment, and
lower-resolution model projections rely on parameterizations
that are only loosely constrained by present day changes. Here
we project that the Antarctic ice sheet will contribute up to 30
cm sea-level equivalent by 2100 and 72 cm by 2200 (95%
quantiles) where the ASE dominates. Our process-based,
statistical approach gives skewed and complex probability
distributions (single mode, 10 cm, at 2100; two modes, 49 cm and
6 cm, at 2200). The dependence of sliding on basal friction is a
key unknown: nonlinear relationships favour higher
contributions. Results are conditional on assessments of MISI
risk on the basis of projected triggers under the climate
scenario A1B (ref. 9), although sensitivity to these is limited
by theoretical and topographical constraints on the rate and
extent of ice loss. We find that contributions are restricted by
a combination of these constraints, calibration with success in
simulating observed ASE losses, and low assessed risk in some
basins. Our assessment suggests that upper-bound estimates from
low-resolution models and physical arguments (up to a metre by
2100 and around one and a half by 2200) are implausible under
current understanding of physical mechanisms and potential
triggers.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Large parts of the Antarctic ice sheet lying on bedrock below
sea level may be vulnerable to marine-ice-sheet instability
(MISI), a self-sustaining retreat of the grounding line
triggered by oceanic or atmospheric changes. There is growing
evidence that MISI may be underway throughout the Amundsen Sea
embayment (ASE), which contains ice equivalent to more than a
metre of global sea-level rise. If triggered in other regions,
the centennial to millennial contribution could be several
metres. Physically plausible projections are challenging:
numerical models with sufficient spatial resolution to simulate
grounding-line processes have been too computationally expensive
to generate large ensembles for uncertainty assessment, and
lower-resolution model projections rely on parameterizations
that are only loosely constrained by present day changes. Here
we project that the Antarctic ice sheet will contribute up to 30
cm sea-level equivalent by 2100 and 72 cm by 2200 (95%
quantiles) where the ASE dominates. Our process-based,
statistical approach gives skewed and complex probability
distributions (single mode, 10 cm, at 2100; two modes, 49 cm and
6 cm, at 2200). The dependence of sliding on basal friction is a
key unknown: nonlinear relationships favour higher
contributions. Results are conditional on assessments of MISI
risk on the basis of projected triggers under the climate
scenario A1B (ref. 9), although sensitivity to these is limited
by theoretical and topographical constraints on the rate and
extent of ice loss. We find that contributions are restricted by
a combination of these constraints, calibration with success in
simulating observed ASE losses, and low assessed risk in some
basins. Our assessment suggests that upper-bound estimates from
low-resolution models and physical arguments (up to a metre by
2100 and around one and a half by 2200) are implausible under
current understanding of physical mechanisms and potential
triggers.
sea level may be vulnerable to marine-ice-sheet instability
(MISI), a self-sustaining retreat of the grounding line
triggered by oceanic or atmospheric changes. There is growing
evidence that MISI may be underway throughout the Amundsen Sea
embayment (ASE), which contains ice equivalent to more than a
metre of global sea-level rise. If triggered in other regions,
the centennial to millennial contribution could be several
metres. Physically plausible projections are challenging:
numerical models with sufficient spatial resolution to simulate
grounding-line processes have been too computationally expensive
to generate large ensembles for uncertainty assessment, and
lower-resolution model projections rely on parameterizations
that are only loosely constrained by present day changes. Here
we project that the Antarctic ice sheet will contribute up to 30
cm sea-level equivalent by 2100 and 72 cm by 2200 (95%
quantiles) where the ASE dominates. Our process-based,
statistical approach gives skewed and complex probability
distributions (single mode, 10 cm, at 2100; two modes, 49 cm and
6 cm, at 2200). The dependence of sliding on basal friction is a
key unknown: nonlinear relationships favour higher
contributions. Results are conditional on assessments of MISI
risk on the basis of projected triggers under the climate
scenario A1B (ref. 9), although sensitivity to these is limited
by theoretical and topographical constraints on the rate and
extent of ice loss. We find that contributions are restricted by
a combination of these constraints, calibration with success in
simulating observed ASE losses, and low assessed risk in some
basins. Our assessment suggests that upper-bound estimates from
low-resolution models and physical arguments (up to a metre by
2100 and around one and a half by 2200) are implausible under
current understanding of physical mechanisms and potential
triggers.
273.
Gregoire, Lauren J; Valdes, Paul J; Payne, Antony J
The relative contribution of orbital forcing and greenhouse gases to the North American deglaciation Journal Article
In: Geophys. Res. Lett., vol. 42, no. 22, pp. 9970–9979, 2015.
@article{Gregoire2015-vx,
title = {The relative contribution of orbital forcing and greenhouse
gases to the North American deglaciation},
author = {Lauren J Gregoire and Paul J Valdes and Antony J Payne},
year = {2015},
date = {2015-11-01},
journal = {Geophys. Res. Lett.},
volume = {42},
number = {22},
pages = {9970–9979},
publisher = {American Geophysical Union (AGU)},
abstract = {AbstractUnderstanding what drove Northern Hemisphere ice sheet
melt during the last deglaciation (21–7 ka) can help constrain
how sensitive contemporary ice sheets are to greenhouse gas
(GHGs) changes. The roles of orbital forcing and GHGs in the
deglaciation have previously been modeled but not yet
quantified. Here for the first time we calculate the relative
effect of these forcings on the North American deglaciation by
driving a dynamical ice sheet model (GLIMMER‐CISM) with a set of
unaccelerated transient deglacial simulations with a full
primitive equation‐based ocean‐atmosphere general circulation
model (FAMOUS). We find that by 9 ka, orbital forcing has caused
50% of the deglaciation, GHG 30%, and the interaction between
the two 20%. Orbital forcing starts affecting the ice volume at
19 ka, 2000 years before CO2 starts increasing in our
experiments, a delay which partly controls their relative
effect.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
AbstractUnderstanding what drove Northern Hemisphere ice sheet
melt during the last deglaciation (21–7 ka) can help constrain
how sensitive contemporary ice sheets are to greenhouse gas
(GHGs) changes. The roles of orbital forcing and GHGs in the
deglaciation have previously been modeled but not yet
quantified. Here for the first time we calculate the relative
effect of these forcings on the North American deglaciation by
driving a dynamical ice sheet model (GLIMMER‐CISM) with a set of
unaccelerated transient deglacial simulations with a full
primitive equation‐based ocean‐atmosphere general circulation
model (FAMOUS). We find that by 9 ka, orbital forcing has caused
50% of the deglaciation, GHG 30%, and the interaction between
the two 20%. Orbital forcing starts affecting the ice volume at
19 ka, 2000 years before CO2 starts increasing in our
experiments, a delay which partly controls their relative
effect.
melt during the last deglaciation (21–7 ka) can help constrain
how sensitive contemporary ice sheets are to greenhouse gas
(GHGs) changes. The roles of orbital forcing and GHGs in the
deglaciation have previously been modeled but not yet
quantified. Here for the first time we calculate the relative
effect of these forcings on the North American deglaciation by
driving a dynamical ice sheet model (GLIMMER‐CISM) with a set of
unaccelerated transient deglacial simulations with a full
primitive equation‐based ocean‐atmosphere general circulation
model (FAMOUS). We find that by 9 ka, orbital forcing has caused
50% of the deglaciation, GHG 30%, and the interaction between
the two 20%. Orbital forcing starts affecting the ice volume at
19 ka, 2000 years before CO2 starts increasing in our
experiments, a delay which partly controls their relative
effect.
274.
Palmer, Steven; McMillan, Malcolm; Morlighem, Mathieu
Subglacial lake drainage detected beneath the Greenland ice sheet Journal Article
In: Nat. Commun., vol. 6, no. 1, pp. 8408, 2015.
@article{Palmer2015-no,
title = {Subglacial lake drainage detected beneath the Greenland ice
sheet},
author = {Steven Palmer and Malcolm McMillan and Mathieu Morlighem},
year = {2015},
date = {2015-10-01},
journal = {Nat. Commun.},
volume = {6},
number = {1},
pages = {8408},
publisher = {Springer Science and Business Media LLC},
abstract = {The contribution of the Greenland ice sheet to sea-level rise
has accelerated in recent decades. Subglacial lake drainage
events can induce an ice sheet dynamic response–a process that
has been observed in Antarctica, but not yet in Greenland, where
the presence of subglacial lakes has only recently been
discovered. Here we investigate the water flow paths from a
subglacial lake, which drained beneath the Greenland ice sheet
in 2011. Our observations suggest that the lake was fed by
surface meltwater flowing down a nearby moulin, and that the
draining water reached the ice margin via a subglacial tunnel.
Interferometric synthetic aperture radar-derived measurements of
ice surface motion acquired in 1995 suggest that a similar event
may have occurred 16 years earlier, and we propose that, as the
climate warms, increasing volumes of surface meltwater routed to
the bed will cause such events to become more common in the
future.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The contribution of the Greenland ice sheet to sea-level rise
has accelerated in recent decades. Subglacial lake drainage
events can induce an ice sheet dynamic response–a process that
has been observed in Antarctica, but not yet in Greenland, where
the presence of subglacial lakes has only recently been
discovered. Here we investigate the water flow paths from a
subglacial lake, which drained beneath the Greenland ice sheet
in 2011. Our observations suggest that the lake was fed by
surface meltwater flowing down a nearby moulin, and that the
draining water reached the ice margin via a subglacial tunnel.
Interferometric synthetic aperture radar-derived measurements of
ice surface motion acquired in 1995 suggest that a similar event
may have occurred 16 years earlier, and we propose that, as the
climate warms, increasing volumes of surface meltwater routed to
the bed will cause such events to become more common in the
future.
has accelerated in recent decades. Subglacial lake drainage
events can induce an ice sheet dynamic response–a process that
has been observed in Antarctica, but not yet in Greenland, where
the presence of subglacial lakes has only recently been
discovered. Here we investigate the water flow paths from a
subglacial lake, which drained beneath the Greenland ice sheet
in 2011. Our observations suggest that the lake was fed by
surface meltwater flowing down a nearby moulin, and that the
draining water reached the ice margin via a subglacial tunnel.
Interferometric synthetic aperture radar-derived measurements of
ice surface motion acquired in 1995 suggest that a similar event
may have occurred 16 years earlier, and we propose that, as the
climate warms, increasing volumes of surface meltwater routed to
the bed will cause such events to become more common in the
future.
275.
Tsamados, Michel; Feltham, Daniel; Petty, Alek; Schroeder, David; Flocco, Daniela
Processes controlling surface, bottom and lateral melt of Arctic sea ice in a state of the art sea ice model Journal Article
In: Philos. Trans. A Math. Phys. Eng. Sci., vol. 373, no. 2052, pp. 20140167, 2015.
@article{Tsamados2015-ij,
title = {Processes controlling surface, bottom and lateral melt of Arctic
sea ice in a state of the art sea ice model},
author = {Michel Tsamados and Daniel Feltham and Alek Petty and David Schroeder and Daniela Flocco},
year = {2015},
date = {2015-10-01},
journal = {Philos. Trans. A Math. Phys. Eng. Sci.},
volume = {373},
number = {2052},
pages = {20140167},
publisher = {The Royal Society},
abstract = {We present a modelling study of processes controlling the summer
melt of the Arctic sea ice cover. We perform a sensitivity study
and focus our interest on the thermodynamics at the
ice-atmosphere and ice-ocean interfaces. We use the Los Alamos
community sea ice model CICE, and additionally implement and
test three new parametrization schemes: (i) a prognostic mixed
layer; (ii) a three equation boundary condition for the salt and
heat flux at the ice-ocean interface; and (iii) a new lateral
melt parametrization. Recent additions to the CICE model are
also tested, including explicit melt ponds, a form drag
parametrization and a halodynamic brine drainage scheme. The
various sea ice parametrizations tested in this sensitivity
study introduce a wide spread in the simulated sea ice
characteristics. For each simulation, the total melt is
decomposed into its surface, bottom and lateral melt components
to assess the processes driving melt and how this varies
regionally and temporally. Because this study quantifies the
relative importance of several processes in driving the summer
melt of sea ice, this work can serve as a guide for future
research priorities.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We present a modelling study of processes controlling the summer
melt of the Arctic sea ice cover. We perform a sensitivity study
and focus our interest on the thermodynamics at the
ice-atmosphere and ice-ocean interfaces. We use the Los Alamos
community sea ice model CICE, and additionally implement and
test three new parametrization schemes: (i) a prognostic mixed
layer; (ii) a three equation boundary condition for the salt and
heat flux at the ice-ocean interface; and (iii) a new lateral
melt parametrization. Recent additions to the CICE model are
also tested, including explicit melt ponds, a form drag
parametrization and a halodynamic brine drainage scheme. The
various sea ice parametrizations tested in this sensitivity
study introduce a wide spread in the simulated sea ice
characteristics. For each simulation, the total melt is
decomposed into its surface, bottom and lateral melt components
to assess the processes driving melt and how this varies
regionally and temporally. Because this study quantifies the
relative importance of several processes in driving the summer
melt of sea ice, this work can serve as a guide for future
research priorities.
melt of the Arctic sea ice cover. We perform a sensitivity study
and focus our interest on the thermodynamics at the
ice-atmosphere and ice-ocean interfaces. We use the Los Alamos
community sea ice model CICE, and additionally implement and
test three new parametrization schemes: (i) a prognostic mixed
layer; (ii) a three equation boundary condition for the salt and
heat flux at the ice-ocean interface; and (iii) a new lateral
melt parametrization. Recent additions to the CICE model are
also tested, including explicit melt ponds, a form drag
parametrization and a halodynamic brine drainage scheme. The
various sea ice parametrizations tested in this sensitivity
study introduce a wide spread in the simulated sea ice
characteristics. For each simulation, the total melt is
decomposed into its surface, bottom and lateral melt components
to assess the processes driving melt and how this varies
regionally and temporally. Because this study quantifies the
relative importance of several processes in driving the summer
melt of sea ice, this work can serve as a guide for future
research priorities.
276.
Wolstencroft, Martin; King, Matt A; Whitehouse, Pippa L; Bentley, Michael J; Nield, Grace A; King, Edward C; McMillan, Malcolm; Shepherd, Andrew; Barletta, Valentina; Bordoni, Andrea; Riva, Riccardo E M; Didova, Olga; Gunter, Brian C
Uplift rates from a new high-density GPS network in Palmer Land indicate significant late Holocene ice loss in the southwestern Weddell Sea Journal Article
In: Geophys. J. Int., vol. 203, no. 1, pp. 737–754, 2015.
@article{Wolstencroft2015-ti,
title = {Uplift rates from a new high-density GPS network in Palmer
Land indicate significant late Holocene ice loss in the
southwestern Weddell Sea},
author = {Martin Wolstencroft and Matt A King and Pippa L Whitehouse and Michael J Bentley and Grace A Nield and Edward C King and Malcolm McMillan and Andrew Shepherd and Valentina Barletta and Andrea Bordoni and Riccardo E M Riva and Olga Didova and Brian C Gunter},
year = {2015},
date = {2015-10-01},
journal = {Geophys. J. Int.},
volume = {203},
number = {1},
pages = {737–754},
publisher = {Oxford University Press (OUP)},
abstract = {The measurement of ongoing ice-mass loss and associated melt
water contribution to sea-level change from regions such as West
Antarctica is dependent on a combination of remote sensing
methods. A key method, the measurement of changes in Earth's
gravity via the GRACE satellite mission, requires a potentially
large correction to account for the isostatic response of the
solid Earth to ice-load changes since the Last Glacial Maximum.
In this study, we combine glacial isostatic adjustment modelling
with a new GPS dataset of solid Earth deformation for the
southern Antarctic Peninsula to test the current understanding
of ice history in this region. A sufficiently complete history
of past ice-load change is required for glacial isostatic
adjustment models to accurately predict the spatial variation of
ongoing solid Earth deformation, once the
independently-constrained effects of present-day ice mass loss
have been accounted for. Comparisons between the GPS data and
glacial isostatic adjustment model predictions reveal a
substantial misfit. The misfit is localized on the southwestern
Weddell Sea, where current ice models under-predict uplift rates
by approximately 2 mm yr−1. This under-prediction suggests that
either the retreat of the ice sheet grounding line in this
region occurred significantly later in the Holocene than
currently assumed, or that the region previously hosted more ice
than currently assumed. This finding demonstrates the need for
further fieldwork to obtain direct constraints on the timing of
Holocene grounding line retreat in the southwestern Weddell Sea
and that GRACE estimates of ice sheet mass balance will be
unreliable in this region until this is resolved.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The measurement of ongoing ice-mass loss and associated melt
water contribution to sea-level change from regions such as West
Antarctica is dependent on a combination of remote sensing
methods. A key method, the measurement of changes in Earth's
gravity via the GRACE satellite mission, requires a potentially
large correction to account for the isostatic response of the
solid Earth to ice-load changes since the Last Glacial Maximum.
In this study, we combine glacial isostatic adjustment modelling
with a new GPS dataset of solid Earth deformation for the
southern Antarctic Peninsula to test the current understanding
of ice history in this region. A sufficiently complete history
of past ice-load change is required for glacial isostatic
adjustment models to accurately predict the spatial variation of
ongoing solid Earth deformation, once the
independently-constrained effects of present-day ice mass loss
have been accounted for. Comparisons between the GPS data and
glacial isostatic adjustment model predictions reveal a
substantial misfit. The misfit is localized on the southwestern
Weddell Sea, where current ice models under-predict uplift rates
by approximately 2 mm yr−1. This under-prediction suggests that
either the retreat of the ice sheet grounding line in this
region occurred significantly later in the Holocene than
currently assumed, or that the region previously hosted more ice
than currently assumed. This finding demonstrates the need for
further fieldwork to obtain direct constraints on the timing of
Holocene grounding line retreat in the southwestern Weddell Sea
and that GRACE estimates of ice sheet mass balance will be
unreliable in this region until this is resolved.
water contribution to sea-level change from regions such as West
Antarctica is dependent on a combination of remote sensing
methods. A key method, the measurement of changes in Earth's
gravity via the GRACE satellite mission, requires a potentially
large correction to account for the isostatic response of the
solid Earth to ice-load changes since the Last Glacial Maximum.
In this study, we combine glacial isostatic adjustment modelling
with a new GPS dataset of solid Earth deformation for the
southern Antarctic Peninsula to test the current understanding
of ice history in this region. A sufficiently complete history
of past ice-load change is required for glacial isostatic
adjustment models to accurately predict the spatial variation of
ongoing solid Earth deformation, once the
independently-constrained effects of present-day ice mass loss
have been accounted for. Comparisons between the GPS data and
glacial isostatic adjustment model predictions reveal a
substantial misfit. The misfit is localized on the southwestern
Weddell Sea, where current ice models under-predict uplift rates
by approximately 2 mm yr−1. This under-prediction suggests that
either the retreat of the ice sheet grounding line in this
region occurred significantly later in the Holocene than
currently assumed, or that the region previously hosted more ice
than currently assumed. This finding demonstrates the need for
further fieldwork to obtain direct constraints on the timing of
Holocene grounding line retreat in the southwestern Weddell Sea
and that GRACE estimates of ice sheet mass balance will be
unreliable in this region until this is resolved.
277.
Armitage, Thomas W K; Ridout, Andy L
Arctic sea ice freeboard from AltiKa and comparison with CryoSat‐2 and Operation IceBridge Journal Article
In: Geophys. Res. Lett., vol. 42, no. 16, pp. 6724–6731, 2015.
@article{Armitage2015-qg,
title = {Arctic sea ice freeboard from AltiKa and comparison with
CryoSat‐2 and Operation IceBridge},
author = {Thomas W K Armitage and Andy L Ridout},
year = {2015},
date = {2015-08-01},
journal = {Geophys. Res. Lett.},
volume = {42},
number = {16},
pages = {6724–6731},
publisher = {American Geophysical Union (AGU)},
abstract = {AbstractSatellite radar altimeters have improved our knowledge
of Arctic sea ice thickness over the past decade. The main
sources of uncertainty in sea ice thickness retrievals are
associated with inadequate knowledge of the snow layer depth and
the radar interaction with the snow pack. Here we adapt a method
of deriving sea ice freeboard from CryoSat‐2 to data from the
AltiKa Ka band radar altimeter over the 2013–14 Arctic sea ice
growth season. AltiKa measures basin‐averaged freeboards between
4.4 cm and 6.9 cm larger than CryoSat‐2 in October and March,
respectively. Using airborne laser and radar measurements from
spring 2013 and 2014, we estimate the effective scattering
horizon for each sensor. While CryoSat‐2 echoes penetrate to the
ice surface over first‐year ice and penetrate the majority (82
$±$ 3%) of the snow layer over multiyear ice, AltiKa echoes
are scattered from roughly the midpoint (46 $±$ 5%) of the
snow layer over both ice types.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
AbstractSatellite radar altimeters have improved our knowledge
of Arctic sea ice thickness over the past decade. The main
sources of uncertainty in sea ice thickness retrievals are
associated with inadequate knowledge of the snow layer depth and
the radar interaction with the snow pack. Here we adapt a method
of deriving sea ice freeboard from CryoSat‐2 to data from the
AltiKa Ka band radar altimeter over the 2013–14 Arctic sea ice
growth season. AltiKa measures basin‐averaged freeboards between
4.4 cm and 6.9 cm larger than CryoSat‐2 in October and March,
respectively. Using airborne laser and radar measurements from
spring 2013 and 2014, we estimate the effective scattering
horizon for each sensor. While CryoSat‐2 echoes penetrate to the
ice surface over first‐year ice and penetrate the majority (82
$±$ 3%) of the snow layer over multiyear ice, AltiKa echoes
are scattered from roughly the midpoint (46 $±$ 5%) of the
snow layer over both ice types.
of Arctic sea ice thickness over the past decade. The main
sources of uncertainty in sea ice thickness retrievals are
associated with inadequate knowledge of the snow layer depth and
the radar interaction with the snow pack. Here we adapt a method
of deriving sea ice freeboard from CryoSat‐2 to data from the
AltiKa Ka band radar altimeter over the 2013–14 Arctic sea ice
growth season. AltiKa measures basin‐averaged freeboards between
4.4 cm and 6.9 cm larger than CryoSat‐2 in October and March,
respectively. Using airborne laser and radar measurements from
spring 2013 and 2014, we estimate the effective scattering
horizon for each sensor. While CryoSat‐2 echoes penetrate to the
ice surface over first‐year ice and penetrate the majority (82
$±$ 3%) of the snow layer over multiyear ice, AltiKa echoes
are scattered from roughly the midpoint (46 $±$ 5%) of the
snow layer over both ice types.
278.
Cornford, S L; Martin, D F; Payne, A J; Ng, E G; Brocq, A M Le; Gladstone, R M; Edwards, T L; Shannon, S R; Agosta, C; Broeke, M R; Hellmer, H H; Krinner, G; Ligtenberg, S R M; Timmermann, R; Vaughan, D G
Century-scale simulations of the response of the West Antarctic Ice Sheet to a warming climate Journal Article
In: Cryosphere, vol. 9, no. 4, pp. 1579–1600, 2015.
@article{Cornford2015-xi,
title = {Century-scale simulations of the response of the West Antarctic
Ice Sheet to a warming climate},
author = {S L Cornford and D F Martin and A J Payne and E G Ng and A M Le Brocq and R M Gladstone and T L Edwards and S R Shannon and C Agosta and M R Broeke and H H Hellmer and G Krinner and S R M Ligtenberg and R Timmermann and D G Vaughan},
year = {2015},
date = {2015-08-01},
journal = {Cryosphere},
volume = {9},
number = {4},
pages = {1579–1600},
publisher = {Copernicus GmbH},
abstract = {Abstract. We use the BISICLES adaptive mesh ice sheet model to
carry out one, two, and three century simulations of the
fast-flowing ice streams of the West Antarctic Ice Sheet,
deploying sub-kilometer resolution around the grounding line
since coarser resolution results in substantial underestimation
of the response. Each of the simulations begins with a geometry
and velocity close to present-day observations, and evolves
according to variation in meteoric ice accumulation rates and
oceanic ice shelf melt rates. Future changes in accumulation and
melt rates range from no change, through anomalies computed by
atmosphere and ocean models driven by the E1 and A1B emissions
scenarios, to spatially uniform melt rate anomalies that remove
most of the ice shelves over a few centuries. We find that
variation in the resulting ice dynamics is dominated by the
choice of initial conditions and ice shelf melt rate and mesh
resolution, although ice accumulation affects the net change in
volume above flotation to a similar degree. Given sufficient
melt rates, we compute grounding line retreat over hundreds of
kilometers in every major ice stream, but the ocean models do
not predict such melt rates outside of the Amundsen Sea
Embayment until after 2100. Within the Amundsen Sea Embayment
the largest single source of variability is the onset of
sustained retreat in Thwaites Glacier, which can triple the rate
of eustatic sea level rise.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract. We use the BISICLES adaptive mesh ice sheet model to
carry out one, two, and three century simulations of the
fast-flowing ice streams of the West Antarctic Ice Sheet,
deploying sub-kilometer resolution around the grounding line
since coarser resolution results in substantial underestimation
of the response. Each of the simulations begins with a geometry
and velocity close to present-day observations, and evolves
according to variation in meteoric ice accumulation rates and
oceanic ice shelf melt rates. Future changes in accumulation and
melt rates range from no change, through anomalies computed by
atmosphere and ocean models driven by the E1 and A1B emissions
scenarios, to spatially uniform melt rate anomalies that remove
most of the ice shelves over a few centuries. We find that
variation in the resulting ice dynamics is dominated by the
choice of initial conditions and ice shelf melt rate and mesh
resolution, although ice accumulation affects the net change in
volume above flotation to a similar degree. Given sufficient
melt rates, we compute grounding line retreat over hundreds of
kilometers in every major ice stream, but the ocean models do
not predict such melt rates outside of the Amundsen Sea
Embayment until after 2100. Within the Amundsen Sea Embayment
the largest single source of variability is the onset of
sustained retreat in Thwaites Glacier, which can triple the rate
of eustatic sea level rise.
carry out one, two, and three century simulations of the
fast-flowing ice streams of the West Antarctic Ice Sheet,
deploying sub-kilometer resolution around the grounding line
since coarser resolution results in substantial underestimation
of the response. Each of the simulations begins with a geometry
and velocity close to present-day observations, and evolves
according to variation in meteoric ice accumulation rates and
oceanic ice shelf melt rates. Future changes in accumulation and
melt rates range from no change, through anomalies computed by
atmosphere and ocean models driven by the E1 and A1B emissions
scenarios, to spatially uniform melt rate anomalies that remove
most of the ice shelves over a few centuries. We find that
variation in the resulting ice dynamics is dominated by the
choice of initial conditions and ice shelf melt rate and mesh
resolution, although ice accumulation affects the net change in
volume above flotation to a similar degree. Given sufficient
melt rates, we compute grounding line retreat over hundreds of
kilometers in every major ice stream, but the ocean models do
not predict such melt rates outside of the Amundsen Sea
Embayment until after 2100. Within the Amundsen Sea Embayment
the largest single source of variability is the onset of
sustained retreat in Thwaites Glacier, which can triple the rate
of eustatic sea level rise.
279.
Tilling, Rachel L; Ridout, Andy; Shepherd, Andrew; Wingham, Duncan J
Increased Arctic sea ice volume after anomalously low melting in 2013 Journal Article
In: Nat. Geosci., vol. 8, no. 8, pp. 643–646, 2015.
@article{Tilling2015-iy,
title = {Increased Arctic sea ice volume after anomalously low melting in
2013},
author = {Rachel L Tilling and Andy Ridout and Andrew Shepherd and Duncan J Wingham},
year = {2015},
date = {2015-08-01},
journal = {Nat. Geosci.},
volume = {8},
number = {8},
pages = {643–646},
publisher = {Springer Science and Business Media LLC},
abstract = {Changes in Arctic sea ice volume are difficult to quantify. Five
years of satellite data reveal a reduction in autumn sea ice
volume in 2010–2012, but a sharp increase in 2013 and 2014,
suggesting that ice volume can recover quickly.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Changes in Arctic sea ice volume are difficult to quantify. Five
years of satellite data reveal a reduction in autumn sea ice
volume in 2010–2012, but a sharp increase in 2013 and 2014,
suggesting that ice volume can recover quickly.
years of satellite data reveal a reduction in autumn sea ice
volume in 2010–2012, but a sharp increase in 2013 and 2014,
suggesting that ice volume can recover quickly.
280.
Wilchinsky, Alexander V; Heorton, Harold D B S; Feltham, Daniel L; Holland, Paul R
Study of the impact of ice formation in leads upon the sea ice pack mass balance using a new frazil and grease ice parameterization Journal Article
In: J. Phys. Oceanogr., vol. 45, no. 8, pp. 2025–2047, 2015.
@article{Wilchinsky2015-zs,
title = {Study of the impact of ice formation in leads upon the sea ice
pack mass balance using a new frazil and grease ice
parameterization},
author = {Alexander V Wilchinsky and Harold D B S Heorton and Daniel L Feltham and Paul R Holland},
year = {2015},
date = {2015-08-01},
journal = {J. Phys. Oceanogr.},
volume = {45},
number = {8},
pages = {2025–2047},
publisher = {American Meteorological Society},
abstract = {AbstractLeads are cracks in sea ice that often form because of
deformation. During winter months, leads expose the ocean to the
cold atmosphere, resulting in supercooling and the formation of
frazil ice crystals within the mixed layer. Here the authors
investigate the role of frazil ice formation in leads on the
mass balance of the sea ice pack through the incorporation of a
new module into the Los Alamos sea ice model (CICE). The frazil
ice module considers an initial cooling of leads followed by a
steady-state formation of uniformly distributed single size
frazil ice crystals that precipitate to the ocean surface as
grease ice. The grease ice is pushed against one of the lead
edges by wind and water drag that the authors represent through
a variable collection thickness for new sea ice. Simulations of
the sea ice cover in the Arctic and Antarctic are performed and
compared to a model that treats leads the same as the open
ocean. The processes of ice formation in the new module slow
down the refreezing of leads, resulting in a longer period of
frazil ice production. The fraction of frazil-derived sea ice
increases from 10% to 50%, corresponding better to
observations. The new module has higher ice formation rates in
areas of high ice concentration and thus has a greater impact
within multiyear ice than it does in the marginal seas. The
thickness of sea ice in the central Arctic increases by over 0.5
m, whereas within the Antarctic it remains unchanged.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
AbstractLeads are cracks in sea ice that often form because of
deformation. During winter months, leads expose the ocean to the
cold atmosphere, resulting in supercooling and the formation of
frazil ice crystals within the mixed layer. Here the authors
investigate the role of frazil ice formation in leads on the
mass balance of the sea ice pack through the incorporation of a
new module into the Los Alamos sea ice model (CICE). The frazil
ice module considers an initial cooling of leads followed by a
steady-state formation of uniformly distributed single size
frazil ice crystals that precipitate to the ocean surface as
grease ice. The grease ice is pushed against one of the lead
edges by wind and water drag that the authors represent through
a variable collection thickness for new sea ice. Simulations of
the sea ice cover in the Arctic and Antarctic are performed and
compared to a model that treats leads the same as the open
ocean. The processes of ice formation in the new module slow
down the refreezing of leads, resulting in a longer period of
frazil ice production. The fraction of frazil-derived sea ice
increases from 10% to 50%, corresponding better to
observations. The new module has higher ice formation rates in
areas of high ice concentration and thus has a greater impact
within multiyear ice than it does in the marginal seas. The
thickness of sea ice in the central Arctic increases by over 0.5
m, whereas within the Antarctic it remains unchanged.
deformation. During winter months, leads expose the ocean to the
cold atmosphere, resulting in supercooling and the formation of
frazil ice crystals within the mixed layer. Here the authors
investigate the role of frazil ice formation in leads on the
mass balance of the sea ice pack through the incorporation of a
new module into the Los Alamos sea ice model (CICE). The frazil
ice module considers an initial cooling of leads followed by a
steady-state formation of uniformly distributed single size
frazil ice crystals that precipitate to the ocean surface as
grease ice. The grease ice is pushed against one of the lead
edges by wind and water drag that the authors represent through
a variable collection thickness for new sea ice. Simulations of
the sea ice cover in the Arctic and Antarctic are performed and
compared to a model that treats leads the same as the open
ocean. The processes of ice formation in the new module slow
down the refreezing of leads, resulting in a longer period of
frazil ice production. The fraction of frazil-derived sea ice
increases from 10% to 50%, corresponding better to
observations. The new module has higher ice formation rates in
areas of high ice concentration and thus has a greater impact
within multiyear ice than it does in the marginal seas. The
thickness of sea ice in the central Arctic increases by over 0.5
m, whereas within the Antarctic it remains unchanged.