Monitoring Change in the Arctic - Satellite-based Applications on Climate Change - page 140

Fig. 9.10 Daily Arctic sea ice extent as of 26 September 2010, along with daily ice extents for
years with the previous four lowest minimum extents. The solid light blue line indicates 2010,
solid dark blue shows 2009, pink shows 2008, dashed green shows 2007, light green shows 2005,
and solid gray indicates average extent from 1979 to 2000. The gray area around the average line
shows the two standard deviation range of the data (Courtesy of the National Snow and Ice Data
Center)
Newer passive microwave sensors, such as the Japanese Advanced Microwave
Scanning Radiometer (AMSR), provide higher spatial resolution data and addi-
tional channels. The newest passive microwave technology is the polarimetric
sensor, like the WindSat/Coriolis instrument. Synthetic aperture radar (SAR), an
active microwave technology, provides detailed images of the ice cover at spatial
resolutions as high as 30 m. The advent of SAR revolutionized the capabilities of
the operational centers, allowing much higher quality analysis including informa-
tion on lead location/orientation, ice type, and new ice formation. SAR instruments
on ERS-1/2, Radarsat, Envisat, and Advanced Land Observing Satellite (ALOS)
provide useful high-resolution information on deformation, leads, ridging, and new
ice production (Fig. 9.11 ).
Scatterometry provides information on a spatial scale similar to that of passive
microwave imagers but can provide better information on perennial ice cover as
well complementary information on other properties due to different sensitivities to
certain characteristics of the ice surface such as snow cover and melt. The ERS-1/
2 and NASA (NSCAT) scatterometers launched in the early and mid-1990s,
respectively, began the scientific application of routine scatterometer data to oper-
ational applications including sea ice. The SeaWinds instrument on the NASA
QuikScat and the Japanese Advanced Earth Observing Satellite (ADEOS) have