Science & Tech
Climate change: Arctic ice volume shows consistent decline
The latest observations on Arctic sea ice from the European Space Agency’s (ESA) Cryosat mission, presented at a symposium in Edinburgh, Scotland, last week, reveal a new record low volume of sea ice in the northern polar region.
It may be too early to draw conclusions from the Cryosat data since this ESA mission to monitor variations in the thickness as well as the extent of polar ice has only been returning data since winter 2010-2011 in the northern hemisphere but the latest measurements on Arctic sea ice volumes reinforce historical data on Arctic sea ice melt from the American Meteorological Society, who last month published their climatic report card for 2012, “State of the Climate in 2012.”
From Cryosat’s most recent data, it could be a case of ‘never mind the width, feel the quality’ when it comes to Arctic sea ice. Over the past two decades or so, satellite data has confirmed a consistent downward trend in the extent of Arctic sea ice but Cryosat returns accurate information on the mass or volume of ice being lost, allowing scientists to obtain a more complete picture of the changes taking place.
Presenting figures at the Living Planet Symposium in Edinburgh last week, Andrew Shepherd, Professor of Earth Observation at the School of Earth and the Environment at Leeds University, UK told delegates, “CryoSat continues to provide clear evidence of diminishing Arctic sea ice.”
Professor Shepherd continued, “From the satellite’s measurements we can see that some parts of the ice pack ice have thinned more rapidly than others, but there has been a decrease in the volume of winter and summer ice over the past three years,” adding, “The volume of the sea ice at the end of last winter was less than 15,000 cubic kilometers, which is lower than any other year going into summer and indicates less winter growth than usual.”
The CryoSat mission has now provided three consecutive measurements of the thickness of Arctic sea ice, from October 2010 to April 2013. The latest data, disclosing a record low volume of ice going into summer 2013, reinforces other studies pointing to a continuing, and in some instances, accelerating loss of northern polar ice.
Towards the end of 2012, in conjunction with Dr Erik Ivins at NASA’s Jet Propulsion Laboratory, Professor Shepherd lead a team of almost 50 researchers who contributed to a paper titled “A reconciled estimate of ice sheet mass balance,” published in the journal ‘Science’. That study, the most accurate assessment of ice losses from Antarctica and Greenland to date, ended 20 years of uncertainty.
Using comprehensive data from a range of satellites, the 2012 study confirmed that both Antarctica and Greenland are losing ice. It also showed that the combined rate of ice sheet melt has increased over time. Altogether, Greenland and Antarctica are now losing more than three times as much ice (equivalent to 0.95 mm of sea level rise per year) as they were in the 1990s (equivalent to 0.27 mm of sea level rise per year).
Cryosat should enable climate scientists to obtain a more complete picture of what is happening with Arctic and Antarctic ice. This year, for example, the ESA says it seems unlikely that a record minimum of sea-ice extent will be set this September. On the face of it, that might seem like good news, at least for climate change skeptics, but the superficial area of Arctic ice only gives a two-dimensional picture of how climate change may be affecting the polar region. From data provided by Cryosat, scientists will be able to establish whether thinner ice at the start of summer 2013 feeds through to a new record low for the actual volume of Arctic ice at the end of winter 2012-13.