Observing the State of Arctic Sea Ice

The state of arctic sea ice is observed by decadal satellite active microwave (AM) and passive microwave (PM) data. We show arctic sea ice change in the context of climatic change from Drift-Age model estimates in the last half century, including dynamic and thermodynamic effects exerted by the atmosphere and ocean.

Perennial ice extent in March rapidly declined at a rate of 1.5 million km2 in this decade, triple the reduction rate during 1970–2000. No significant trend was found for the 1950s and 1960s. A record was set in the reduction of arctic perennial ice extent in winter 2008, while the winter total sea ice extent has been stable compared to the average over the decade of the AM data record. Satellite and surface data records confirm that the reduction of winter perennial ice extent broke the record in 2008 during the last half century, which is matched again in 2009.

We assess the consistency in derivations of sea ice extent from AM (QuikSCAT) and PM (NT2 algorithm). Furthermore, AM sea ice results have been ingested into the Seasonal Ice Zone Observing Network (www.sizonet.org). Comparisons with ice thickness profiling and sea-ice coring north of Alaska show good correspondence between perennial ice classification from satellite data and ground truth. These results have been contributed to the Sea Ice Outlook, a community effort under the Study of Environmental Arctic Change program.

Different patterns of co-existing high and low pressure anomalies can energize the Polar Express, causing significant dynamic loss of perennial ice. The drastic reduction of perennial ice significantly decreases the overall surface albedo, resulting in enhanced solar heat absorption, which further decreases the arctic ice pack through the ice-albedo feedback mechanism and ice melt from the underside. Maps of sea ice class distribution, closely conforming to patterns of the regional bathymetry, indicate effects of oceanic water masses controlled by bathymetry on sea ice formation.

Sea ice information around the North Pole (NP) becomes more critical to support field measurement campaigns. Thus, the AM method is advanced to enable daily observations of arctic sea ice classes as close as 42 km to the NP. Results reveal that the boundary of perennial sea ice crossed the NP in February 2008. Combining AM and SAR data can automatically classify sea ice and identify small features like polynyas and leads, as verified by the Circumpolar Flaw Lead System Study.