Great popsci BBC piece. Please follow the link for loads of enriched media including data visualization, etc.
http://www.bbc.co.uk/news/science-environment-17803691 A By Jonathan Amos Science correspondent, BBC News, Vienna Europe's Cryosat mission is now watching the ebb and flow of Arctic sea ice with high precision. The radar spacecraft was launched in 2010 to monitor changes in the thickness and shape of polar ice.. Scientists have spent the past two years getting to grips with its data. And on Tuesday, they reported that Cryosat was now delivering an unprecedented view of the seasonal growth and retreat of sea ice spanning the entire Arctic basin. The researchers also released a map showing the difference in height across the Greenland ice sheet. Click the two tabs above to see visualisations of the satellite's data. "The message is that Cryosat is working extremely well. Its data are very reliable and the measurements we have match reality," said Prof Volker Liebig, the director of Earth Observation at the European Space Agency "We now have a very powerful tool to monitor the changes taking place at the poles," he told The Esa director delivered an update on the mission at London's Royal Society. The information was also being released here at the European Geosciences Union (EGU) meeting in Vienna, Austria. Several satellites have already detailed the recent and rapid erosion of summer sea ice extent as the Arctic has But Cryosat's innovation has been to provide a means to get at a figure for ice volume - a far more significant number in terms of understanding the long-term viability of the ice. To do this, the satellite carries one of the highest resolution synthetic aperture radars ever put in orbit. The instrument sends down pulses of microwave energy which bounce off both the top of the ice and the water in the cracks, or leads, which By measuring the difference in height between these two surfaces, scientists can, using a relatively simple calculation, work out the overall volume of the marine cover. How to measure sea-ice thickness from space Cryosat's radar has the resolution to see the Arctic's floes and leads Some 7/8ths of the ice tends to sit below the waterline - the draft The aim is to measure the freeboard - the ice part above the waterline Knowing this 1/8th figure allows Cryosat to work out sea ice thickness The thickness multiplied by the area of ice cover produces a volume The Cryosat team, led from University College London, has spent the period since launch working through the satellite's measurements, validating and calibrating them against a number of independent These include data from plane-borne instruments, from direct on-the-ice assessments, and even from scientific sea-floor moorings that profile the ice floes as they pass overhead. "We can now say with good confidence that Cryosat's maps of ice thickness are correct to within 10-20cm," said Dr Seymour Laxon, from UCL's Centre for Polar Observation and Modelling (CPOM). Tuesday's release shows a complete seasonal cycle, from October 2010, when the Arctic Ocean was beginning to freeze up following the summer melt, right through to March 2011, The Cryosat team has been "in the field"to when the sea ice was approaching peak validate the satellite's measurements thickness. Cryosat found the volume (area multiplied by thickness) of sea ice in the central Arctic in March 2011 to have been 14,500 cubic kilometres. This figure is very similar to that suggested by PIOMAS (Panarctic Ice Ocean Modeling and Assimilation System), an influential computer model that has been used to estimate Arctic sea ice volume, and which has been the basis for several predictions about when summer sea ice in the north might disappear completely. In addition to the announcement on sea ice, the Cryosat team also published a digital elevation model (DEM) of Greenland. The big island, too, has experienced some rapid changes of late and is losing tens of billions of tonnes of its ice cover to the ocean annually. The DEM is a map of varying height, and the visualisation on this page incorporates a year's worth of data. For Cryosat, it is another illustration of its capability. Radar satellites have traditionally struggled to discern the detail in the steep slopes and ridges that mark the edges of ice sheets, but the Esa spacecraft can recover far more information thanks to a special interferometric observing mode that uses "This is really the first demonstration of the Jonathan Amos took a look around Cryosat before its interferometer in action," said Prof Andrew launch in 2010 Shepherd from Leeds University. "The DEM contains about 7.5 million data points, and we're pretty confident this will be the best elevation model for Greenland, by some margin. Our next step is to compare it to previous data to see how Greenland has changed." Cryosat's principal investigator, Prof Duncan Wingham - formerly of UCL but now chief executive of the UK's National Environment Research Council - summed up: "We have years of data to come, but I think it's quite clear that we will provide synoptic, accurate, Arctic-wide thickness; and that we will be able to determine the accuracy of the predictions of when the Arctic will be ice-free in Summer. "And I think it's also clear we can now sustain coverage of [ice sheets on Antarctica and Greenland] right down to the coast." The Cryosat update was timed to coincide with this week's 50th anniversary of UK activity in orbit. April 1962 was the month Britain became a space-faring nation with the launch of its first satellite, Ariel-1. As part of the celebration, current capabilities and missions with strong UK interest are being highlighted. Cryosat's map of Arctic sea ice thickness - April 2011 [email protected] and follow me on Twitter -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en.
