CryoSat-2 mission reveals major Arctic sea-ice loss
13th Feb 2013
Credit: CPOM/UCL/ESA/UW-APL/NSIDC/PVL. View HD version.
Arctic sea ice volume has declined by 36 per cent in the autumn and 9 per cent in the winter between 2003 and 2012, a UK-led team of scientists has discovered.
Researchers, led by Professor Seymour Laxon, used new data from the European Space Agency’s CryoSat-2 satellite spanning 2010 to 2012, and data from NASA’s ICESat satellite from 2003 to 2008 to estimate the volume of sea ice in the Arctic.
They found that from 2003 to 2008, autumn volumes of ice averaged 11,900 km3. But from 2010 to 2012, the average volume had dropped to 7600 km3 – a decline of 4300 km3. The average ice volume in the winter from 2003 to 2008 was 16,300 km3, dropping to 14,800 km3 between 2010 and 2012 – a difference of 1500 km3.
‘The data reveals that thick sea ice has disappeared from a region to the north of Greenland, the Canadian Archipelago, and to the northeast of Svalbard,’ says Dr Katharine Giles, a NERC-funded research fellow at the Centre for Polar Observation and Modelling (CPOM) at UCL (University College London), who co-authored the report, published online in Geophysical Research Letters.
The findings confirm the continuing decline in Arctic sea-ice volume simulated by the Pan-Arctic Ice-Ocean Modelling and Assimilation System (PIOMAS), which estimates the volume of Arctic sea ice and had been checked using earlier submarine, mooring, and satellite observations until 2008.
Other satellites have already shown drops in the area covered by Arctic sea ice as the climate has warmed. Indeed, sea-ice extent reached a record minimum in September 2012. But CryoSat-2, launched in April 2010, differs in that it lets scientists estimate the volume of sea ice – a much more accurate indicator of the changes taking place in the Arctic.
‘While two years of CryoSat-2 data aren’t indicative of a long-term change, the lower ice thickness and volume in February and March 2012, compared with same period in 2011, may have contributed to the record minimum ice extent during the 2012 autumn,’ says Professor Christian Haas of York University, Canada Research Chair for Arctic Sea Ice Geophysics, co-author of the study and coordinator of the international CryoSat sea ice validation activities.
CryoSat-2 measures ice volume using a high-resolution synthetic aperture radar altimeter, which fires pulses of microwave energy down towards the ice. The energy bounces off both the top of sections of ice and the water in the cracks in between. The difference in height between these two surfaces let scientists calculate the volume of the ice cover.
The findings are the result of a huge international collaboration between teams from UCL, the European Space Agency, the Jet Propulsion Laboratory, the University of Washington, York University, Alfred Wegener Institute for Polar and Marine Research, Woods Hole Oceanographic Institution, Morgan State University and the University of Maryland.
The team confirmed CryoSat-2 estimates of ice volume using measurements from three independent sources – aircraft, moorings, and NASA’s Operation IceBridge.
The research was funded by the Natural Environment Research Council, the European Space Agency, the German Aerospace Center, Alberta Ingenuity, NASA, the Office of Naval Research and the National Science Foundation.
The first map of Arctic sea-ice seasonal variability, generated by CPOM, was presented at the Royal Society on Tuesday 24th April. The map, using data from ESA's Cryosat-2, shows the changes in sea-ice thickness over the period October 2010 to March 2011. Read more at ESA and BBC.
First Globice project datasets released
The UCL-led ESA Globice project to model sea ice dynamics using radar data from the Envisat and ERS missions has released its first validated datasets for the Arctic winters of 2004–11 Read more here:
Western Arctic Ocean freshwater storage increased by wind-driven spin-up of the Beaufort Gyre
CPOM scientists have discovered that the freshwater stored in the western Arctic Ocean has increased by 8000 km3 between the mid 1990s and 2010 by looking at changes in the sea surface height measured by the European Space Agency Satellites ERS-2 and Envisat.
This increase in fresh water corresponds to an increase in the anti-cyclonicity (clockwise in the Northern Hemisphere) of the wind over the western Arctic. Anti-cyclonic winds move the surface waters so that they pile up in the centre of the anti-cyclone, doming the sea surface. These findings are reported in Nature Geoscience (publication date - 22nd Jan 2012). Models had suggested that the action of the wind on the sea surface could cause a raised dome of freshwater to form in the middle of the Beaufort Gyre, but until now, there had been no continuous observations of sea-surface height to categorically demonstrate this. A reversal of the wind could lead to the release of this fresh water into the rest of the Arctic Ocean and possibly beyond.
Lead author, Katharine Giles says “We were surprised to find that our results also suggested that something else was going on. When we looked at our data on a year-to-year basis we noticed that the changes in the sea surface height did not always follow what the wind was doing so we thought about reasons as to why this might happen. One idea is that sea ice forms a barrier between the atmosphere and the ocean. So, as the sea-ice cover changes, the effect of the wind on the ocean might also change.”
UCL Lunch Hour Lecture: Here Katharine Giles describes the results from this paper (between minutes 10 and 20) along with an introduction about the Arctic sea ice and ocean, the use of satellites to monitor it, in particular CryoSat-2. UCL Lunch Hour Lecture youtube channel http://www.youtube.com/watch?v=xYxyv8WUQjo.
BBC news article here.
Duncan Wingham presents the results from the first year of the CryoSat-2 mission at the Paris Air and Space show. Watch here.
Since the launch last year CPOM and European Space Agency (ESA) scientists have been examining the data and designing new processing systems to turn measurements made from 700 km in space into maps of the ice cover in the Arctic and Antarctic and of the Arctic Ocean surface. Today marked the culmination of that effort with the presentation of the first ice maps from CryoSat-2. They reveal for the first time, throughout the entire Arctic, the detailed behaviour of the ice as it is rifted and redistributed by the action of the wind. As CryoSat-2 continues to send back measurements from its polar orbit they will build up a detailed picture of how the ice cover and ocean are changing.
Robert Cullen from ESA says "It's really heart warming to start to see the results of all the difficult work European industry has put into this mission. They were really pressured with a tight specification to work with. Since launch it's also been a hard year trying to understand the data of a new measurement system and CPOM at the forefront with ESA and international support now has the capability of starting to deliver on the CryoSat mission objectives. After one year this is a real achievement and one we should all be proud of."
The sea-ice thickness map is based on data from January and February 2011 and shows thicker, rough, multi-year ice north of Canada and Greenland, stretching to the North Pole and slightly beyond. In large parts of the Arctic – north of Russia – the map reveals thinner, first year ice. The black line marks the boundary between the first year and multi-year ice from data from The Norwegian Meteorological Institute.
Seymour Laxon (Director of CPOM) says "This is the first time we have been able to measure sea ice thickness over almost the entire Arctic ice pack. The thickness map shows a clear agreement with regional data gathered from aircraft, demonstrating that CryoSat-2 now provides us with a tool to accurately measure changes in ice thickness."
Analysis of CryoSat-2 data, by CPOM scientist Natalia Galin, over a test site near the Hawaiian-Emperor Seamount Chain in the Pacific Ocean has also revealed the superb accuracy of the CryoSat-2 instrument. Natalia says “We were astonished to find we could measure tiny changes in the ocean surface caused by the seamounts lying deep under water. We didn’t believe the hardware was capable of this. It makes us think that this technology might have an interesting future for ocean applications too.”
CPOM scientist Katharine Giles says: "CryoSat-2 will not only reveal what is happening to the Arctic sea ice but also how the ocean beneath is changing. The Arctic Ocean itself contains a large amount of liquid fresh water and changes to the Arctic Ocean circulation can effect how this water is stored and its release into the North Atlantic."
This figure shows the Arctic Ocean Sea Surface Height for January and February 2011 from CryoSat-2. The sea surface height is the height above the Earth's gravity field in meters and has been combined with data from the Envisat satellite in areas where there is no ice cover.
In April 2011 three members of CPOM, Rosie Willatt, Katharine Giles and Seymour Laxon, headed to the far north of Canada to participate in experiments to validate CryoSat measurements over sea ice.
Links to their individual blogs can be found on the ESA Cryosat Blog here.
Hotter summers may not be as catastrophic for the Greenland ice sheet as previously feared and may actually slow down the flow of glaciers, according to new research. A letter published in Nature on 27 January explains how increased melting in warmer years causes the internal drainage system of the ice sheet to 'adapt' and accommodate more melt-water, without speeding up the flow of ice toward the oceans. The findings have important implications for future assessments of global sea level rise. The Greenland ice sheet covers roughly 80% of the surface of the island and contains enough water to raise sea levels by 7 metres if it were to melt completely. Rising temperatures in the Arctic in recent years have caused the ice sheet to shrink, prompting fears that it may be close to a 'tipping point' of no return.
For the BBC News report please click here.
CPOM have generated the first scientific result from CryoSat: Arctic Dynamic Topography. Dynamic Topography is generated by subtracting a model of the gravity field from the sea surface topography measured by CryoSat and Envisat. The map reveals details of the topography including a large gyre in the Beaufort Sea north of Canada and the Transpolar drift out of the Arctic.
For the BBC News report please click here.
CPOM scientists have discovered that changes in the amount of ice floating in the polar oceans are causing sea levels to rise. The research, published this week in Geophysical Research Letters, is the first assessment of how quickly floating ice is being lost today. According to Archimedes' principle, any floating object displaces its own weight of fluid. For example, an ice cube in a glass of water does not cause the glass to overflow as it melts. But because sea water is warmer and more salty than floating ice, changes in the amount of this ice are having an effect on global sea levels. The loss of floating ice is equivalent to 1.5 million Titanic-sized icebergs each year. However, the study shows that spread across the global oceans, recent losses of floating ice amount to a sea level rise of just 49 micrometers per year - about a hair's breadth.
For the Telegraph News report please click here.
ESA PR 07-2010. Europe's first mission dedicated to studying the Earth’s ice was launched today from Kazakhstan. From its polar orbit, CryoSat-2 will send back data leading to new insights into how ice is responding to climate change and the role it plays in our 'Earth system'.
The CryoSat-2 satellite was launched at 15:57 CEST (13:57 UTC) on a Dnepr rocket provided by the International Space Company Kosmotras from the Baikonur Cosmodrome in Kazakhstan. The signal confirming that it had separated from the launcher came 17 minutes later from the Malindi ground station in Kenya. More...
For the BBC News report on the launch please click here.
The most comprehensive picture of the rapidly thinning glaciers along the coastline of both the Antarctic and Greenland ice sheets has been created using satellite lasers. The findings are an important step forward in the quest to make more accurate predictions for future sea level rise. Reporting in Nature, researchers from British Antarctic Survey and the University of Bristol (School of Geographical Sciences) describe how analysis of millions of NASA satellite measuremetns from both of these vast ice sheets shows that the most profound ice loss is a result of glaciers speeding up where they flow into the sea.
The CryoSat2 mission is ready to map the ice fields of the Arctic and the Antarctic; Duncan Wingham explains the mission on BBC News - "Ice mission returns for second go". More...
Duncan Wingham talks to The Observer ("Britains ice man ready for a second space shot with rebuilt CryoSat probe") on the importance of launching the CryoSat-2 probe to study the impact of global warming on the Arctic and Antarctic ice. More...
According to a new study led by Duncan Wingham the thinning of the gigantic glacier in Antarctica is accelerating. The research, funded by the UK Natural Environment Research Council, shows that the Pine Island Glacier in West Antarctica is losing ice four times as fast as it was a decade ago. More...
Please click here for the UCL Press Release
Last winter, the thickness of sea ice in large parts of the Arctic fell by nearly half a metre (19 per cent) compared with the average thickness of the previous five winters. This followed the dramatic 2007 summer low when Arctic ice extent dropped to its lowest level since records began.
Up until last winter, the thickness of Arctic sea ice showed a slow downward trend during the previous five winters, but after the summer 2007 record low extent, the thickness of the ice also nose-dived. What is concerning is that sea ice is not just receding but it is also thinning.
Steve Palmer has been awarded a fellowship by the Japan Society for the Promotion of Science to fund a visit to the Japanese National Institute for Polar Research (NIPR). Whilst at NIPR, Steve will use satellite remote sensing to observe changes in the velocity of the Shirase glacier in East Antarctica. The fellowship covers the costs of a three month visit, which Steve expects to take up some time during the next year.
The Philip Leverhulme Prizes were established to reward outstanding young scholars of substantial distinction and promise; the Prizes commemorate the late Third Viscount Leverhulme, who died in 2000. The prize announcement states:
"Dr Shepherd's research uses satellite remote sensing to advance our understanding of the motion of large ice sheets, such as those in Greenland and Antarctica. Using sophisticated quantitative techniques, he has been able to provide continental-scale information on the rate and pattern of ice sheet melt over periods of several years. As a result, he is an authority on how large ice sheets are resonding to and influencing global environments, and is making major contributions to our understanding of global environmental change more generally."
16 March 2007
After a century of polar exploration, the past decade of satellite measurements has painted an altogether new picture of how Earth's ice sheets are changing. As global temperatures have risen, so have rates of snowfall, ice melting, and glacier flow. Although the balance between these opposing processes has varied considerably on a regional scale, data show that Antarctica and Greenland are each losing mass overall. Click here to see the paper and links to other related Science articles.
Articles relating to the paper can also be found in the Guardian, Independent and Washington Post.
2 December 2006
CPOM research on a rapid discharge from an Antarctic sub-glacial lake recently published in Nature has been featured on the front cover of the 2nd December special issue of the New Scientist on the "Hidden World Beneath Antarctica's Ice". The full article and New Scientist's weekly podcast discussing this feature can be found on the New Scientist website.
The Philip Leverhulme Prizes were established to reward outstanding young scholars of substantial distinction and promise. The prize announcement states:
"Daniel Feltham has made major contributions to our understanding of the formation of ice in polar seas. This plays an important role in the interaction between the polar oceans and the overlying atmosphere and has a long-term effect on climate. He has developed theoretical models, confirmed by laboratory experimentation and tested against data from field experiments, of the mechanical and thermodynamic properties of sea ice. Of particular importance is his model, one of the very first in this area, of the evolution of melt-water ponds which form on the surface of ice during the summer. These melt ponds can considerably lower the albedo, which is a measure of the reflectivity and hence the degree of input solar radiation that is reflected, rather than captured, of the Earth's surface. Dr Feltham has already established himself as one of the scientific leaders in this field, building a group tackling central problems in this area. His future research will focus on the interactions between polar oceans, sea ice and ice shelves and the processes that drive the global redistribution of heat by the ocean."
The existence of many subglacial lakes provides clear evidence for the widespread presence of water beneath the Antarctic ice sheet. Recent studies by CPOM staff of ice-sheet surface elevation changes indicate that these lakes, far from being a static ecosystem cut off from each other, are in fact connected. Changes indicating a rapid discharge of water from one lake to another were detected, and it is possible that the entire subglacial drainage basin is flushed through periodically by massive water transfers. Click here to see the paper and links to other related Nature articles.
At the latest meeting of the European Space Agency's Earth Observation Programme Board, which took place at ESA's Headquarters in Paris on 23 and 24 February, ESA received the green light from its Member States to build and launch a CryoSat recovery mission, CryoSat-2. The launch of the CryoSat spacecraft was unfortunately aborted on 8 October 2005 due to a malfunction of its Rockot launcher, which resulted in the total loss of the spacecraft.