CryoSat-2 - the ice mission

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CryoSat-2 - the ice mission

6 April 2010

At 14:57 UK time, Thursday 8 April, the European Space Agency will launch its third Earth Explorer satellite CryoSat-2 from the Baikonur cosmodrome in Kazakhstan.

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How CryoSat-2 will give scientists detailed information about changes in ice cover at the poles

The UK-led mission will measure the shape and thickness of Arctic and Antarctic ice with unprecedented accuracy.

Although scientists know the ice caps are melting, they're not sure how melting polar ice affects ocean circulation patterns, sea level and climate. And because the poles are difficult to access, the only way to get this information is by using satellites.

CryoSat-2's ability to monitor changes at the poles will surpass the abilities of earlier ESA satellites - its radar has been specifically designed for the task and its orbit will cover much more of the Arctic than was previously possible.

Sue Nelson speaks to Professor Duncan Wingham, principal investigator of the mission at University College London, to find out more.

Keywords: Antarctic, Arctic, Environmental change, Oceans, Polar,

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Are the ice caps melting? I refer to recent postings and graphs from NSIDC Boulder , Colorado, showing recent arctic sea ice well within "normal" amounts, and incresing over the last four years, and a comment that Antarctica sea ice is seemingly increasing overall by some 3% over the last decade.Who is right?

richarddonnellan, Teignmouth, U.K
Tuesday, 6 April 2010 - 15:52

Hello Richard,

The picture on Arctic sea ice is still complex. The extent of sea ice has rebounded from the low point reached in 2006 over the last few years, but the long-term trend is still negative.

The NSIDC's latest report came out yesterday. Here's how it summarises recent developments:

"Arctic sea ice extent averaged for March 2010 was 15.10 million square kilometers (5.83 million square miles). This was 650,000 square kilometers (250,000 square miles) below the 1979 to 2000 average for March, but 670,000 square kilometers (260,000 square miles) above the record low for the month, which occurred in March 2006.

Ice extent was above normal in the Bering Sea and Baltic Sea, but remained below normal over much of the Atlantic sector of the Arctic, including the Baffin Bay, and the Canadian Maritime Provinces seaboard. Extent in other regions was near average."

There's been a rebound in sea ice extent late in the season due to colder-than-usual weather. ("This March, low atmospheric pressure systems persisted over the Gulf of Alaska and north of Scandinavia. These pressure patterns led to unusually cold conditions and persistent northerly winds in the Bering and Barents Seas, which pushed the ice edge southward in these two regions.") This means we've reached what's probably the year's maximum extent of sea ice later in the year than usual - later in fact than any other year since satellite records started in 1979.

The long-term trend still looks like one of falling sea-ice extent, as figure 3 on the NSIDC page above ('Average monthly arctic sea ice extent March 1979 to 2010') shows. Short-term fluctuations don't prove a great deal either way.

Also worth bearing in mind is that the new satellite will monitor both Arctic and Antarctic ice, and that the area covered by ice isn't the only important factor; ice thickness is also very significant and Cryosat will give us more information about this.

Tom Marshall, Planet Earth Online
Wednesday, 7 April 2010 - 14:29

Dear Richard

As Tom points out, just as with temperatures here in the UK, you really can't tell much from a month or two of data and the long terms trends in Arctic ice extent are certainly downwards. As for the Antarctic it's worth pointing out that historically most of the sea ice cover in the Antarctic is seasonal whilst the Arctic has, or used to have, mostly permanent ice cover. That means that changes in the Arctic sea ice are more indicative of long term trends than for Antarctic sea ice.

Also as Tom points out a critical issue is not just the sea ice extent but also its thickness. We have had satellites up to look at this for some time and all appear to show a thinning (e.g. Laxon, Nature, 2003; Giles, GRL, 2008, Kwok, JGR, 2009) as do submarine data (Rothrock, GRL, 1999). However all of these data are limited in time and/or spatial coverage and the satellites, in particular, are not designed for the job so the data is not as well sampled as we would like.

So, in addition to obtaining data over the large ice caps, CryoSat is aimed to get us the best view as to how sea thickness is changing in the Arctic.

Seymour Laxon
Director of the Centre for Polar Observation and Modelling
CryoSat Principal Investigator

Seymour Laxon, London
Monday, 12 April 2010 - 14:14

The accuracy of the measurements is absolutely staggering but I suspect that a 5 year mission is unlikely to settle arguments given Tom's comments on variations over the last 40 years. But we have to start somewhere and this looks like being an important contribution - I hope Planet Earth will be able to provide regular up-dates.

Mike Welch, United Kingdom
Monday, 12 April 2010 - 16:39

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