This week we watched along with many across the globe, as pioneer European satellite ERS-2 finally made its journey back to earth after almost 30 years monitoring earth from the sky.
For many current and former CPOM scientists, this was an emotional moment, as the data from this satellite has made (and continues to make) an integral contribution to understanding the cryosphere. In fact, CPOM Director Professor Andrew Shepherd used ERS-2 data for his first paper 23 years ago ‘Inland Thinning of Pine Island Glacier, West Antarctica’ which used satellite altimetry and interferometry to show that the glacier ‘had thinned by up to 1.6 meters per year between 1992 and 1999’.
Part of the European Space Agency’s (ESA) earth observation programme, the revolutionary satellite was launched in April 1995 into a sun-synchronous polar orbit at an altitude of around 800 km, and was one of the most powerful and sophisticated satellites of its time.
Due to its three-axis stabilization it was able to point directly towards our planet and could observe most areas of the earth, using SAR (Synthetic Aperture Radar) to view land surfaces, polar ice and oceans, measuring ocean-surface temperature, sea winds and sea level changes via Radar Altimetry. On top of this it could also monitor ozone levels.
The data this satellite collected has been crucial in monitoring land surface changes, warming oceans, natural disasters, and importantly for the Centre for Polar Observation and Modelling – monitoring diminishing polar ice and sea-level rise. ERS-2 (and it’s twin ERS-1 launched a few years prior) paved the way for other programmes including the EU Space program’s Copernicus Sentinels and ESA’s CryoSat Earth Explore Mission, both of which continue to provide vital data for CPOM’s research. In fact, we are using ERS-2 data to extend our datasets further back in time, in order to create a fuller view of the evolution of the cryosphere over the last 30 years.
It was retired in 2011 and has been de-orbiting since then. Now it’s 16-year journey home is complete, broken and burned up in the atmosphere with the remaining parts landing safely in the ocean yesterday but even though the physical entity is gone, the data it produced, having been used for thousands of scientific papers, continues to provide information for scientists at ESA, CPOM and beyond.
New research states that future rises in sea level could be better estimated by gaining a clearer understanding of the Antarctic and Greenland ice sheets.
Global climate change and its impact on sea levels is a pressing issue and trying to accurately predict just how much they will rise in future is subject to ongoing analysis. The changing nature of ice sheets is a vital factor in the projection of future sea level rise.
Led by the University of Lincoln and involving Dr Sammie Buzzard from the Centre for Polar Observation and Modelling (Northumbria University), the paper was published today in the Nature journal, Nature Reviews Earth & Environment.
An important aspect of the review highlights that short-term fluctuations in climate could have an amplification feedback effect, meaning that ice sheets are more sensitive to climate change than previously understood.
During the melt season (typically from May to September) on the Greenland ice sheet, water collects in depressions on the surface of the ice, creating supraglacial lakes. If these lakes have enough water and the right conditions, they can crack open (hydrofracture) which allows water to flow from the ice surface down to the bedrock underneath, where it acts like a lubricant. These lakes on the Greenland ice sheet are incredibly important, but identifying exactly how deep they are using satellite data is difficult.
This research compares different ways of measuring the depth of these supraglacial lakes, using tools including a radiative transfer equation (RTE), ArcticDEM digital elevation models, and ICESat-2 photon refraction. The team of researchers led by CPOM PhD Researcher Laura Melling (Lancaster University) applied these methods to five lakes in southwest Greenland.
The paper examines the uncertainty in these estimates, which affects our understanding of the total lake volume and how that, in turn, can interfere with predictions about how fast the ice is moving. This work demonstrates how combining information from multiple different satellite sources can improve our ability to track meltwater on top of the Greenland Ice Sheet.
Authors include: CPOM PhD Researcher Laura Melling (Lancaster University), CPOM Associate Investigator Amber Leeson, CPOM Principal Investigator Malcolm McMillan (Lancaster University), CPOM Senior Research Associate Jennifer Maddalena (Lancaster University), Jade Bowling (Lancaster University), CPOM PhD Researcher Emily Glen (Lancaster University), Louise Sandberg Sørensen (Technical University of Denmark), Mai Winstrup (Technical University of Denmark), and Rasmus Lørup Arildsen (Technical University of Denmark).
CPOM publishes paper on ‘Multipeak retracking‘ introducing a new processing approach, aimed at overcoming challenges associated with using radar altimetry to measure ice sheet changes over rugged coastal topography in Antarctica and Greenland.
This new MultiPeak processing approach which is applied to data from the Copernicus Sentinel-3 mission, significantly improves the accuracy and quantity of elevation retrievals and and has the potential to enhance the capability of SAR altimeters to track ice sheet imbalance. This is an important step forward in developing more sophisticated monitoring approaches for tracking ice loss in the most complex regions which contribute to global seal level rise. The paper is co-authored by CPOM Senior Research Associate Dr Qi Huang (Lancaster University), CPOM Associate Investigator Professor Mal McMillan (Lancaster University), CPOM Systems, Data, Product Manager Alan Muir (UCL), CPOM Affiliate Joe Phillips (Lancaster University) and CPOM Research Fellow Dr Thomas Slater (Northumbria University).
The seven worst years for polar ice sheets melting and losing ice have occurred during the past decade, according to new research, with 2019 being the worst year on record.
The melting ice sheets now account for a quarter of all sea level rise a fivefold increase since the 1990’s according to IMBIE, an international team of researchers who have combined 50 satellite surveys of Antarctica and Greenland taken between 1992 and 2020.
Global heating is melting the polar ice sheets, driving up sea levels and coastal flooding around our planet. Ice losses from Greenland and Antarctica can now be reliably measured from space by tracking changes in their volume, gravitational pull, or ice flow. NASA and the European Space Agency (ESA) and awarded funding to the Ice Sheet Mass Balance Intercomparison Exercise (IMBIE) in 2011 to compile the satellite record of polar ice sheet melting. Data collected by the team is widely used by leading organisations, including by the Intergovernmental Panel on Climate Change (IPCC).
In their latest assessment, the IMBIE Team which is led by Northumbria University’sCentre for Polar Observations and Modelling have combined 50 satellite surveys of Antarctica and Greenland to determine their rate of ice melting. They have found that Earth’s polar ice sheets lost 7,560 billion tonnes of ice between 1992 and 2020 equivalent to an ice cube that would be 20 kilometres in height.
The polar ice sheets have together lost ice in every year of the satellite record, and the seven highest melting years have occurred in the past decade.
The satellite records show that 2019 was the record melting year when the ice sheets lost a staggering 612 billion tonnes of ice.
This loss was driven by an Arctic summer heatwave, which led to record melting from Greenland peaking at 444 billion tonnes that year. Antarctica lost 168 billion tonnes of ice the sixth highest on record due to the continued speedup of glaciers in West Antarctica and record melting from the Antarctic Peninsula. The East Antarctic Ice Sheet remained close to a state of balance, as it has throughout the satellite era.
Melting of the polar ice sheets has caused a 21 mm rise in global sea level since 1992, almost two thirds (13.5 mm) of which has originated from Greenland and one third (7.4 mm) from Antarctica.
In the early 1990s, ice sheet melting accounted for only a small fraction (5.6 %) of sea level rise. However, there has been a fivefold increase in melting since then, and they are now responsible for more than a quarter (25.6 %) of all sea level rise. If the ice sheets continue to lose mass at this pace, the IPCC predicts that they will contribute between 148 and 272 mm to global mean-sea level by the end of the century.
After a decade of work we are finally at the stage where we can continuously update our assessments of ice sheet mass balance as there are enough satellites in space monitoring them, which means that people can make use of our findings immediately.
Ice losses from Greenland and Antarctica have rapidly increased over the satellite record and are now a major contributor to sea level rise. Continuously monitoring the ice sheets is critical to predict their future behaviour in a warming world and adapt for the associated risks that coastal communities around the world will face.
This is now the third assessment of ice loss produced by the IMBIE team, due to continued cooperation between the space agencies and the scientific community. The first and second assessments were published in 2012 and 2018/19.
Over the past few years, ESA and NASA have made a dedicated effort to launch new satellite missions capable of monitoring the polar regions. The IMBIE project has taken advantage of these to produce more regular updates, and, for the first time, it is now possible to chart polar ice sheet losses every year.
This third assessment from the IMBIE Team, funded by the ESA and NASA, involved a team of 68 polar scientists from 41 international organisations using measurements from 17 satellite missions, including for the first time from the GRACE-FO gravity mission. Importantly, it brings the records of ice loss from Antarctica and Greenland in line, using the same methods and covering the same period in time. The assessment will now be updated annually to make sure that the scientific community has the very latest estimates of polar ice losses.
Dr Diego Fernandez, Head of Research and Development at ESA, said:
This is another milestone in the IMBIE initiative and represent an example of how scientists can coordinate efforts to assess the evolution of ice sheets from space offering unique and timely information on the magnitude and onset of changes.
The new annual assessments represent a step forward in the way IMBIE will help to monitor these critical regions, where variations have reached a scale where abrupt changes can no longer be excluded.
The UKRI have awarded £47M to NERC research centres to address six critical environmental science challenges facing the UK, including climate change mitigation strategies, coastal flooding & erosion, and extreme weather.
CPOM is to collaborate on 3 projects BIOPOLE, CANARI & TerraFIRMA.
Biogeochemical processes and ecosystem function in a changing polar system (BIOPOLE), £9 million
Led by the British Antarctic Survey, in collaboration with:
British Geological Survey
Centre for Polar Observation and Modelling
National Oceanography Centre
UK Centre for Ecology & Hydrology.
Project partners include:
Alfred Wegener Institute, Germany
Helmholtz Centre for Polar and Marine Research, Germany
University of Alaska Fairbanks, USA
University of Alberta, Canada
University of Bristol, UK
University Centre in Svalbard, Norway.
Climate change is proceeding faster at the poles than any other region, resulting in sea ice loss and glacial melting.
There is a clear urgency in understanding the full implications of these changes for the polar regions themselves and for the wider Earth system.
BIOPOLE will provide a step change in the knowledge and predictive capability concerning how polar ecosystems regulate the chemical balance of the world’s oceans and, through it, their effect on global fish stocks and carbon storage.
Climate change in the Arctic-North Atlantic region and impact on the UK (CANARI), £12 million
Led by the National Centre for Atmospheric Science, in collaboration with:
British Antarctic Survey
British Geological Survey
Centre for Polar Observation and Modelling
National Centre for Earth Observation
National Oceanography Centre
UK Centre for Ecology & Hydrology.
The project partner is the Met Office Hadley Centre, UK.
The weather and climate of the UK is shaped by the large-scale circulation of the atmosphere and ocean in the North Atlantic.
This project will advance understanding of the impacts on the UK arising from climate variability and change in the Arctic-North Atlantic region. It will focus on extreme weather and the potential for rapid, disruptive change.
This will enable the UK to play an internationally leading role in addressing the challenges of understanding regional climate change and provide detailed information about impacts on the UK.
Future impacts risks and mitigation actions (TerraFIRMA), £9.5 million
Led by the National Centre for Atmospheric Science, in collaboration with:
British Antarctic Survey
British Geological Survey
Centre for Polar Observation and Modelling
National Centre for Earth Observation
National Oceanography Centre
Plymouth Marine Laboratory
UK Centre for Ecology & Hydrology.
Project partner is the Met Office Hadley Centre, UK.
This project will provide reliable guidance on the risks and impacts of future climate change. It will assess a range of mitigation strategies:
impacts on allowable carbon budgets and pathways to net zero
wider environmental, economic and societal impacts, for example, sustainable development goals
As global temperatures increase, the melting of the massive ice sheets that blanket Antarctica and Greenland has accelerated, making a significant contribution to sea-level rise. In total, Earth is losing around a trillion tonnes of ice each year which is not being replenished.
CPOM director, Andrew Shepherd of the University of Leeds is a leading climate scientist working with ESA and NASA. Join Andrew as he discusses how long-term satellite observations from ESA’s Climate Change Initiative are key in monitoring changes in ice sheets over decades.
Global warming has caused extreme ice melting events in Greenland to become more frequent and more intense over the past 40 years according to new research, raising sea levels and flood risk worldwide
Over the past decade alone, 3.5 trillion tonnes of ice has melted from the surface of the island and flowed downhill into the ocean.
That’s enough melted ice to cover the entire UK with around 15 metres of meltwater, or cover the entire city of New York with around 4,500 metres.
The new study, led by the University of Leeds, is the first to use satellite data to detect this phenomena known as ice sheet runoff from space.
The findings, published in Nature Communications, reveal that Greenland’s meltwater runoff has risen by 21% over the past four decades and has become 60% more erratic from one summer to the next.
Important step Lead author Dr Thomas Slater, a Research Fellow in Leeds Centre for Polar Observation and Modelling, said: As we’ve seen with other parts of the world, Greenland is also vulnerable to an increase in extreme weather events.
As our climate warms, it’s reasonable to expect that the instances of extreme melting in Greenland will happen more often observations such as these are an important step in helping us to improve climate models and better predict what will happen this century.
The study, funded by the European Space Agency (ESA) as part of its Polar+Surface Mass Balance Feasibility project, used measurements from the ESA’s CryoSat-2 satellite mission.
The research shows that over the past decade (2011 to 2020), increased meltwater runoff from Greenland raised the global sea level by one centimetre. One-third of this total was produced in just two hot summers (2012 and 2019), when extreme weather led to record-breaking levels of ice melting not seen in the past 40 years.
Raised sea levels caused by ice melt heightens the risk of flooding for coastal communities worldwide and disrupts marine ecosystems in the Arctic Ocean that indigenous communities rely on for food.
It can also alter patterns of ocean and atmospheric circulation which affect weather conditions around the planet.
Extreme weather During the past decade, runoff from Greenland has averaged 357 billion tonnes per year, reaching a maximum of 527 billion tonnes of ice melt in 2012, when changes in atmospheric patterns caused unusually warm air to sit over much of the ice sheet. This was more than twice the minimum runoff of 247 billion tonnes that occurred in 2017.
The changes are related to extreme weather events, such as heatwaves, which have become more frequent and are now a major cause of ice loss from Greenland because of the runoff they produce.
Dr Slater said: There are, however, reasons to be optimistic. We know that setting and meeting meaningful targets to cut emissions could reduce ice losses from Greenland by a factor of three, and there is still time to achieve this.
These first observations of Greenland runoff from space can also be used to verify how climate models simulate ice sheet melting which, in turn, will allow improved predictions of how much Greenland will raise the global sea level in future as extreme weather events become more common.
Greater understanding Study co-author Dr Amber Leeson, Senior Lecturer in Environmental Data Science at Lancaster University, said: Model estimates suggest that the Greenland ice sheet will contribute between about 3 and 23 cm to global sea-level rise by 2100.
This prediction has a wide range, in part because of uncertainties associated with simulating complex ice melt processes, including those associated with extreme weather. These new spaceborne estimates of runoff will help us to understand these complex ice melt processes better, improve our ability to model them, and thus enable us to refine our estimates of future sea level rise.
Finally, the study shows that satellites are able to provide instant estimates of summer ice melting, which supports efforts to expand Greenland’s hydropower capacity and Europe’s ambition to launch the CRISTAL mission to succeed CryoSat-2.
ESA’s CryoSat mission manager, Tommaso Parrinello, said: Since it was launched over 11 years ago, CryoSat has yielded a wealth of information about our rapidly changing polar regions. This remarkable satellite remains key to scientific research and the indisputable facts, such as these findings on meltwater runoff, that are so critical to decision-making on the health of our planet.
Looking further to the future, the Copernicus Sentinel Expansion mission CRISTAL will ensure that Earth’s vulnerable ice will be monitored in the coming decades. In the meantime, it is imperative that CryoSat remains in orbit for as long as possible to reduce the gap before these new Copernicus missions are operational.
An article led by CPOM PhD researcher Inès Otosaka “Surface Melting Drives Fluctuations in Airborne Radar Penetration in West Central Greenland” has been published in Geophysical Research Letters (August 2020).
Radar waves emitted by satellites can be used to measure changes in surface elevation of the Greenland Ice Sheet. However, they do not reflect off the ice sheet surface itself, but penetrate into the snow to a depth of about 15 m for radar wavelengths of 2.3 cm. When the snow melts, meltwater can percolate into the snow or refreeze at the surface. Layers of refrozen ice sharply reduce the degree of radar penetration and may be mistaken for an elevation increase in radar measurements. In this paper, the researchers combine firn cores and modelled firn densities with seven years of airborne radar data collected during field campaigns in West Central Greenland to quantify this effect. They identify internal layers corresponding to annual stratigraphy within the snowpack and show that more melt means less radar penetration into the firn. The unprecedented surface melting which occurred across Greenland in 2012 caused a sharp reduction in the degree of radar penetration, from 11.5 m to 5.3 m. However, if the effects of penetration are corrected for, radar altimeters can accurately measure the surface elevation of the ice sheet.
