@article{Gong2014-vg,

title = {Modelling the response of the Lambert Glacier–Amery Ice Shelf 

 system, East Antarctica, to uncertain climate forcing over the 

 21st and 22nd centuries},

author = {Y Gong and S L Cornford and A J Payne},

year  = {2014},

date = {2014-06-01},

journal = {Cryosphere},

volume = {8},

number = {3},

pages = {1057–1068},

publisher = {Copernicus GmbH},

abstract = {Abstract. The interaction between the climate system and the 

 large polar ice sheet regions is a key process in global 

 environmental change. We carried out dynamic ice simulations of 

 one of the largest drainage systems in East Antarctica: the 

 Lambert Glacier–Amery Ice Shelf system, with an adaptive mesh 

 ice sheet model. The ice sheet model is driven by surface 

 accumulation and basal melt rates computed by the FESOM 

 (Finite-Element Sea-Ice Ocean Model) ocean model and the RACMO2 

 (Regional Atmospheric Climate Model) and LMDZ4 (Laboratoire de 

 Météorologie Dynamique Zoom) atmosphere models. The 

 change of ice thickness and velocity in the ice shelf is mainly 

 influenced by the basal melt distribution, but, although the ice 

 shelf thins in most of the simulations, there is little 

 grounding line retreat. We find that the Lambert Glacier 

 grounding line can retreat as much as 40 km if there is 

 sufficient thinning of the ice shelf south of Clemence Massif, 

 but the ocean model does not provide sufficiently high melt 

 rates in that region. Overall, the increased accumulation 

 computed by the atmosphere models outweighs ice stream 

 acceleration so that the net contribution to sea level rise is 

 negative.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Howard2014-tw,

title = {The land-ice contribution to 21st-century dynamic sea level rise},

author = {T Howard and J Ridley and A K Pardaens and R T W L Hurkmans and A J Payne and R H Giesen and J A Lowe and J L Bamber and T L Edwards and J Oerlemans},

year  = {2014},

date = {2014-06-01},

journal = {Ocean Sci.},

volume = {10},

number = {3},

pages = {485–500},

publisher = {Copernicus GmbH},

abstract = {Abstract. Climate change has the potential to influence global 

 mean sea level through a number of processes including (but not 

 limited to) thermal expansion of the oceans and enhanced land 

 ice melt. In addition to their contribution to global mean sea 

 level change, these two processes (among others) lead to local 

 departures from the global mean sea level change, through a 

 number of mechanisms including the effect on spatial variations 

 in the change of water density and transport, usually termed 

 dynamic sea level changes. In this study, we focus on the 

 component of dynamic sea level change that might be given by 

 additional freshwater inflow to the ocean under scenarios of 

 21st-century land-based ice melt. We present regional patterns 

 of dynamic sea level change given by a global-coupled 

 atmosphere–ocean climate model forced by spatially and 

 temporally varying projected ice-melt fluxes from three sources: 

 the Antarctic ice sheet, the Greenland Ice Sheet and small 

 glaciers and ice caps. The largest ice melt flux we consider is 

 equivalent to almost 0.7 m of global mean sea level rise over 

 the 21st century. The temporal evolution of the dynamic sea 

 level changes, in the presence of considerable variations in the 

 ice melt flux, is also analysed. We find that the dynamic sea 

 level change associated with the ice melt is small, with the 

 largest changes occurring in the North Atlantic amounting to 3 

 cm above the global mean rise. Furthermore, the dynamic sea 

 level change associated with the ice melt is similar regardless 

 of whether the simulated ice fluxes are applied to a simulation 

 with fixed CO2 or under a business-as-usual greenhouse gas 

 warming scenario of increasing CO2.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Schroder2014-sz,

title = {September Arctic sea-ice minimum predicted by spring melt-pond 

 fraction},

author = {David Schröder and Daniel L Feltham and Daniela Flocco and Michel Tsamados},

year  = {2014},

date = {2014-05-01},

journal = {Nat. Clim. Chang.},

volume = {4},

number = {5},

pages = {353–357},

publisher = {Springer Science and Business Media LLC},

abstract = {Prediction of seasonal Arctic sea-ice extent is of increased 

 interest as the region opens up due to climate change. This work 

 uses spring melt-pond area to forecast the Arctic sea-ice 

 minimum in September. This proves accurate, as increasing 

 melt-ponds reduce surface albedo, allowing more melt to occur, 

 creating a positive feedback mechanism.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Tsamados2014-ri,

title = {Impact of variable atmospheric and oceanic form drag on 

 simulations of Arctic sea ice},

author = {Michel Tsamados and Daniel L Feltham and David Schroeder and Daniela Flocco and Sinead L Farrell and Nathan Kurtz and Seymour W Laxon and Sheldon Bacon},

year  = {2014},

date = {2014-05-01},

journal = {J. Phys. Oceanogr.},

volume = {44},

number = {5},

pages = {1329–1353},

publisher = {American Meteorological Society},

abstract = {Abstract Over Arctic sea ice, pressure ridges and floe and melt 

 pond edges all introduce discrete obstructions to the flow of 

 air or water past the ice and are a source of form drag. In 

 current climate models form drag is only accounted for by tuning 

 the air–ice and ice–ocean drag coefficients, that is, by 

 effectively altering the roughness length in a surface drag 

 parameterization. The existing approach of the skin drag 

 parameter tuning is poorly constrained by observations and fails 

 to describe correctly the physics associated with the air–ice 

 and ocean–ice drag. Here, the authors combine recent 

 theoretical developments to deduce the total neutral form drag 

 coefficients from properties of the ice cover such as ice 

 concentration, vertical extent and area of the ridges, freeboard 

 and floe draft, and the size of floes and melt ponds. The drag 

 coefficients are incorporated into the Los Alamos Sea Ice Model 

 (CICE) and show the influence of the new drag parameterization 

 on the motion and state of the ice cover, with the most 

 noticeable being a depletion of sea ice over the west boundary 

 of the Arctic Ocean and over the Beaufort Sea. The new 

 parameterization allows the drag coefficients to be coupled to 

 the sea ice state and therefore to evolve spatially and 

 temporally. It is found that the range of values predicted for 

 the drag coefficients agree with the range of values measured in 

 several regions of the Arctic. Finally, the implications of the 

 new form drag formulation for the spinup or spindown of the 

 Arctic Ocean are discussed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Petty2014-pp,

title = {Sea ice and the ocean mixed layer over the Antarctic shelf seas},

author = {A A Petty and P R Holland and D L Feltham},

year  = {2014},

date = {2014-04-01},

journal = {Cryosphere},

volume = {8},

number = {2},

pages = {761–783},

publisher = {Copernicus GmbH},

abstract = {Abstract. An ocean mixed-layer model has been incorporated into 

 the Los Alamos sea ice model CICE to investigate regional 

 variations in the surface-driven formation of Antarctic shelf 

 waters. This model captures well the expected sea ice thickness 

 distribution, and produces deep (> 500 m) mixed layers in the 

 Weddell and Ross shelf seas each winter. This results in the 

 complete destratification of the water column in deep southern 

 coastal regions leading to high-salinity shelf water (HSSW) 

 formation, and also in some shallower regions (no HSSW 

 formation) of these seas. Shallower mixed layers are produced in 

 the Amundsen and Bellingshausen seas. By deconstructing the 

 surface processes driving the mixed-layer depth evolution, we 

 show that the net salt flux from sea ice growth/melt dominates 

 the evolution of the mixed layer in all regions, with a smaller 

 contribution from the surface heat flux and a negligible input 

 from wind stress. The Weddell and Ross shelf seas receive an 

 annual surplus of mixing energy at the surface; the Amundsen 

 shelf sea energy input in autumn/winter is balanced by energy 

 extraction in spring/summer; and the Bellingshausen shelf sea 

 experiences an annual surface energy deficit, through both a low 

 energy input in autumn/winter and the highest energy loss in 

 spring/summer. An analysis of the sea ice mass balance 

 demonstrates the contrasting mean ice growth, melt and export in 

 each region. The Weddell and Ross shelf seas have the highest 

 annual ice growth, with a large fraction exported northwards 

 each year, whereas the Bellingshausen shelf sea experiences the 

 highest annual ice melt, driven by the advection of ice from the 

 northeast. A linear regression analysis is performed to 

 determine the link between the autumn/winter mixed-layer 

 deepening and several atmospheric variables. The Weddell and 

 Ross shelf seas show stronger spatial correlations (temporal 

 mean – intra-regional variability) between the autumn/winter 

 mixed-layer deepening and several atmospheric variables compared 

 to the Amundsen and Bellingshausen. In contrast, the Amundsen 

 and Bellingshausen shelf seas show stronger temporal 

 correlations (shelf sea mean – interannual variability) between 

 the autumn/winter mixed-layer deepening and several atmospheric 

 variables.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Stroeve2014-xo,

title = {Predicting September sea ice: Ensemble skill of the SEARCH Sea 

 Ice Outlook 2008-2013},

author = {Julienne Stroeve and Lawrence C Hamilton and Cecilia M Bitz and Edward Blanchard-Wrigglesworth},

year  = {2014},

date = {2014-04-01},

journal = {Geophys. Res. Lett.},

volume = {41},

number = {7},

pages = {2411–2418},

publisher = {American Geophysical Union (AGU)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Morris2014-pt,

title = {Densification of polar snow: Measurements, modeling, and 

 implications for altimetry},

author = {E M Morris and D J Wingham},

year  = {2014},

date = {2014-02-01},

journal = {J. Geophys. Res. Earth Surf.},

volume = {119},

number = {2},

pages = {349–365},

publisher = {American Geophysical Union (AGU)},

abstract = {Density profiles in the upper 10–14 m of snow have been 

 measured along a 500 km traverse across the Greenland ice sheet, 

 using a neutron scattering technique. Repeat measurements, over 

 periods ranging from a few days to 5 years, allow strain rates 

 to be determined as a function of depth. Very large strain rates 

 are observed in the surface layer of snow over summer periods. 

 In the underlying multiyear snow, strain rate decreases with 

 decreasing porosity. However, once this effect has been removed, 

 the effect of increasing overburden pressure is counteracted by 

 increasing strength of the material. There are fluctuations in 

 strain rate associated with the annual layering, which indicate 

 that winter and summer snow have different strengths. Based on 

 these observations, we derive a new densification equation which 

 includes the effect of snow density and snow type, and the 

 effect of temperature, described by an Arrhenius expression with 

 activation energy of the order of 110 kJ mol−1 and an 

 exponential prefactor determined simply by the temperature 

 history of the snow. For multiyear snow and meteorological 

 conditions that do not vary from year to year, our equation 

 reduces to a form similar to the Herron and Langway equation for 

 first‐stage densification. Using the new equation, we calculate 

 the sensitivity of compaction rate to short‐term fluctuations in 

 temperature and accumulation as 0.11–0.20 m a−1 K−1 and 

 0.33–0.95 m a−1(meters water equivalent)−1, respectively, and 

 discuss the consequent uncertainty in satellite measurements of 

 the long‐term elevation trend in this area of the Greenland ice 

 sheet.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Stroeve2014-hk,

title = {Changes in Arctic melt season and implications for sea ice loss},

author = {J C Stroeve and T Markus and L Boisvert and J Miller and A Barrett},

year  = {2014},

date = {2014-02-01},

journal = {Geophys. Res. Lett.},

volume = {41},

number = {4},

pages = {1216–1225},

publisher = {American Geophysical Union (AGU)},

abstract = {AbstractThe Arctic‐wide melt season has lengthened at a rate of 

 5 days decade−1 from 1979 to 2013, dominated by later autumn 

 freezeup within the Kara, Laptev, East Siberian, Chukchi, and 

 Beaufort seas between 6 and 11 days decade−1. While melt onset 

 trends are generally smaller, the timing of melt onset has a 

 large influence on the total amount of solar energy absorbed 

 during summer. The additional heat stored in the upper ocean of 

 approximately 752 MJ m−2 during the last decade increases sea 

 surface temperatures by 0.5 to 1.5 °C and largely explains the 

 observed delays in autumn freezeup within the Arctic Ocean's 

 adjacent seas. Cumulative anomalies in total absorbed solar 

 radiation from May through September for the most recent pentad 

 locally exceed 300–400 MJ m−2 in the Beaufort, Chukchi, and 

 East Siberian seas. This extra solar energy is equivalent to 

 melting 0.97 to 1.3 m of ice during the summer.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Favier2014-lr,

title = {Retreat of Pine Island Glacier controlled by marine ice-sheet 

 instability},

author = {L Favier and G Durand and S L Cornford and G H Gudmundsson and O Gagliardini and F Gillet-Chaulet and T Zwinger and A J Payne and A M Le Brocq},

year  = {2014},

date = {2014-02-01},

journal = {Nat. Clim. Chang.},

volume = {4},

number = {2},

pages = {117–121},

publisher = {Springer Science and Business Media LLC},

abstract = {At present the Pine Island Glacier in West Antarctica is 

 thinning and its grounding line has retreated. This work uses 

 three ice-flow models to investigate the stability of the 

 glacier and finds that the grounding line could retreat a 

 further 40 km, which is equivalent to a rise in sea level of 

 3.5–10 mm over a 20 year period.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Roberts2014-ii,

title = {A new constraint on the size of Heinrich Events from an 

 iceberg/sediment model},

author = {William H G Roberts and Paul J Valdes and Antony J Payne},

year  = {2014},

date = {2014-01-01},

journal = {Earth Planet. Sci. Lett.},

volume = {386},

pages = {1–9},

publisher = {Elsevier BV},

abstract = {Heinrich Layers, anomalously thick layers of ice-borne sediment 

 in the North Atlantic ocean, have long been associated with 

 abrupt climate changes in glacial times. However, there is still 

 no consensus on either the exact amount of ice needed to 

 transport this sediment or how such a large volume of ice could 

 be produced. Using an iceberg model that includes sediment, we 

 simulate the delivery of sediment to the North Atlantic during 

 such an event. Our model assumes that sediment is uniformly 

 distributed within the ice with a concentration of 4%. Unlike 

 sediment models which assume that the sediment lies in a single 

 layer, this model can carry sediment all the way from the 

 western to the eastern North Atlantic. We use a variety of 

 different estimates for the total volume of ice released to 

 model the sediment layer thickness and we show that to best fit 

 the observations 60$times$104km3 (with a plausible range of 

 30–120$times$104 km3) of ice needs to be released. This is 

 equivalent to a 0.04 Sv (106m3s−1, with a plausible range of 

 0.02–0.08 Sv) release of freshwater over the 500 yr of a 

 typical Heinrich Event. This is a smaller flux of water than is 

 required to show a significant impact on the global climate in 

 most current ``state of the art'' GCMs.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wright2014-ek,

title = {Subglacial hydrological connectivity within the Byrd Glacier 

 catchment, East Antarctica},

author = {A P Wright and D A Young and J L Bamber and J A Dowdeswell and A J Payne and D D Blankenship and M J Siegert},

year  = {2014},

date = {2014-01-01},

journal = {J. Glaciol.},

volume = {60},

number = {220},

pages = {345–352},

publisher = {Cambridge University Press (CUP)},

abstract = {AbstractIce, Cloud and land Elevation Satellite (ICESat) 

 repeat-track laser altimetry has identified 17 sites within the 

 Byrd Glacier catchment, East Antarctica, where rapid ice-surface 

 height changes have occurred, which have been interpreted as 

 evidence for `active' subglacial lakes. Here we present evidence 

 from a new radio-echo sounding (RES) survey at 11 of these 

 locations to understand the bed conditions associated with the 

 proposed hydrological activity. At none of the sites examined 

 did we find evidence in support of substantial pooled basal 

 water. In the majority of cases, along-track RES bed reflection 

 amplitudes either side of the locations of surface height change 

 are indistinguishable from those within the features. These 

 results indicate that, in most cases, hypothesized `active' 

 lakes are not discrete radar targets and are therefore much 

 smaller than the areas of surface height change. In addition, we 

 have identified three new relatively large subglacial lakes 

 upstream of the region where most `active' subglacial lakes are 

 found, in an area where the hydraulic gradient is significantly 

 lower. Our results suggest that substantial and long-lasting 

 basal water storage in the Byrd Glacier catchment occurs only 

 under low hydraulic gradients, while coast-proximal sites of 

 hydraulic activity likely involve small or temporary 

 accumulations of basal water.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Armitage2014-zk,

title = {Using the interferometric capabilities of the ESA CryoSat-2 

 mission to improve the accuracy of sea ice freeboard retrievals},

author = {Thomas W K Armitage and Malcolm W J Davidson},

year  = {2014},

date = {2014-01-01},

journal = {IEEE Trans. Geosci. Remote Sens.},

volume = {52},

number = {1},

pages = {529–536},

publisher = {Institute of Electrical and Electronics Engineers (IEEE)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Edwards2014-tw,

title = {Effect of uncertainty in surface mass balance–elevation 

 feedback on projections of the future sea level contribution of 

 the Greenland ice sheet},

author = {T L Edwards and X Fettweis and O Gagliardini and F Gillet-Chaulet and H Goelzer and J M Gregory and M Hoffman and P Huybrechts and A J Payne and M Perego and S Price and A Quiquet and C Ritz},

year  = {2014},

date = {2014-01-01},

journal = {Cryosphere},

volume = {8},

number = {1},

pages = {195–208},

publisher = {Copernicus GmbH},

abstract = {Abstract. We apply a new parameterisation of the Greenland ice 

 sheet (GrIS) feedback between surface mass balance (SMB: the sum 

 of surface accumulation and surface ablation) and surface 

 elevation in the MAR regional climate model (Edwards et al., 

 2014) to projections of future climate change using five ice 

 sheet models (ISMs). The MAR (Modèle Atmosphérique 

 Régional: Fettweis, 2007) climate projections are for 

 2000–2199, forced by the ECHAM5 and HadCM3 global climate 

 models (GCMs) under the SRES A1B emissions scenario. The 

 additional sea level contribution due to the SMB–elevation 

 feedback averaged over five ISM projections for ECHAM5 and three 

 for HadCM3 is 4.3% (best estimate; 95% credibility interval 

 1.8–6.9%) at 2100, and 9.6% (best estimate; 95% credibility 

 interval 3.6–16.0%) at 2200. In all results the elevation 

 feedback is significantly positive, amplifying the GrIS sea 

 level contribution relative to the MAR projections in which the 

 ice sheet topography is fixed: the lower bounds of our 95% 

 credibility intervals (CIs) for sea level contributions are 

 larger than the ``no feedback'' case for all ISMs and GCMs. Our 

 method is novel in sea level projections because we propagate 

 three types of modelling uncertainty – GCM and ISM structural 

 uncertainties, and elevation feedback parameterisation 

 uncertainty – along the causal chain, from SRES scenario to sea 

 level, within a coherent experimental design and statistical 

 framework. The relative contributions to uncertainty depend on 

 the timescale of interest. At 2100, the GCM uncertainty is 

 largest, but by 2200 both the ISM and parameterisation 

 uncertainties are larger. We also perform a perturbed parameter 

 ensemble with one ISM to estimate the shape of the projected sea 

 level probability distribution; our results indicate that the 

 probability density is slightly skewed towards higher sea level 

 contributions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Edwards2014-fu,

title = {Probabilistic parameterisation of the surface mass 

 balance–elevation feedback in regional climate model 

 simulations of the Greenland ice sheet},

author = {T L Edwards and X Fettweis and O Gagliardini and F Gillet-Chaulet and H Goelzer and J M Gregory and M Hoffman and P Huybrechts and A J Payne and M Perego and S Price and A Quiquet and C Ritz},

year  = {2014},

date = {2014-01-01},

journal = {Cryosphere},

volume = {8},

number = {1},

pages = {181–194},

publisher = {Copernicus GmbH},

abstract = {Abstract. We present a new parameterisation that relates surface 

 mass balance (SMB: the sum of surface accumulation and surface 

 ablation) to changes in surface elevation of the Greenland ice 

 sheet (GrIS) for the MAR (Modèle Atmosphérique 

 Régional: Fettweis, 2007) regional climate model. The 

 motivation is to dynamically adjust SMB as the GrIS evolves, 

 allowing us to force ice sheet models with SMB simulated by MAR 

 while incorporating the SMB–elevation feedback, without the 

 substantial technical challenges of coupling ice sheet and 

 climate models. This also allows us to assess the effect of 

 elevation feedback uncertainty on the GrIS contribution to sea 

 level, using multiple global climate and ice sheet models, 

 without the need for additional, expensive MAR simulations. We 

 estimate this relationship separately below and above the 

 equilibrium line altitude (ELA, separating negative and positive 

 SMB) and for regions north and south of 77° N, from a set of MAR 

 simulations in which we alter the ice sheet surface elevation. 

 These give four ``SMB lapse rates'', gradients that relate SMB 

 changes to elevation changes. We assess uncertainties within a 

 Bayesian framework, estimating probability distributions for 

 each gradient from which we present best estimates and 

 credibility intervals (CI) that bound 95% of the probability. 

 Below the ELA our gradient estimates are mostly positive, 

 because SMB usually increases with elevation: 0.56 (95% CI: 

 −0.22 to 1.33) kg m−3 a−1 for the north, and 1.91 (1.03 to 2.61) 

 kg m−3 a−1 for the south. Above the ELA, the gradients are much 

 smaller in magnitude: 0.09 (−0.03 to 0.23) kg m−3 a−1 in the 

 north, and 0.07 (−0.07 to 0.59) kg m−3 a−1 in the south, because 

 SMB can either increase or decrease in response to increased 

 elevation. Our statistically founded approach allows us to make 

 probabilistic assessments for the effect of elevation feedback 

 uncertainty on sea level projections (Edwards et al., 2014).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}