The extent of Arctic sea ice is one of the most accessible sources of data showing the effect of global climate change. The National Snow and Ice Data Center (NSIDC) began monitoring Arctic sea ice extents in 1978 using passive microwave satellites at a resolution of 25 km. September 2007 was the lowest summer Arctic sea ice extent observed since NSIDC began monitoring and recording sea ice extents in 1978.
This year according to the NSIDC Arctic sea ice extent is below the 1979 to 2000 average and above the extent for 2007. The southern route of the Northwest Passage is free of sea ice according to imagery from the University of Bremen and the NSIDC Multisensor Analyzed Sea Ice Extent (MASIE) analyses.
Data from the Advanced Microwave Scanning Radiometer – Earth Observing System (AMSR-E) sensor, processed by the University of Bremen, show ice tracking near 2007 levels. The AMSR-E instrument has higher resolution (6.25 km) than the Defense Meteorological Satellite Program (DMSP) F17 Special Sensor Microwave Imager/Sounder (SSMIS) with 25 km resolution.
Ice volume
Estimating ice volume requires a computer model. The University of Washington's Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) model combines data on sea ice concentration with models of ocean and atmospheric conditions to estimate total ice volume. Estimates generated by the model suggest that ice volume is not only well below the 1979 to 2010 average, but below the volume for 2007. The PIOMAS model forecasts that this year's minimum volume in the next month will be below 2007 and could even reach a record low volume.
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