Geoscience Reference
In-Depth Information
In some respects, these losses have been balanced by improved satellite remote
sensing capabilities. Routine Arctic coverage began in the early 1970s with the
polar-orbiting U.S. Air Force Defense Meteorological Satellite Program (DMSP)
system and the National Oceanographic and Atmospheric Administration's
(NOAA) Television Infrared Observation Satellite (TIROS), carrying the Very High
Resolution Radiometer (VHRR). The visible and infrared channels on these plat-
forms provided for the first useful satellite-based assessments of sea ice extent and
concentration and information on synoptic and sub-synoptic cloud systems. The late
1970s saw the first of an ongoing series of TIROS-N systems with the Advanced
VHRR (AVHRR) and the TIROS Operational Vertical Spectrometer (TOVS).
Data sets of cloud cover, surface radiation fluxes, and sea ice motion derived from
AVHRR are finding wide use by the community. TOVS data are assimilated along
with profiles from radiosondes (balloon-borne sounding instruments) and other data
sources in numerical weather prediction models. Since 1999, as part of the National
Aeronautics and Space Administration's (NASA) Earth Observing System (EOS),
the Moderate Resolution Imaging Spectro-Radiometer (MODIS), flow on both the
Aqua and Terra satellites, has provided high resolution coverage of clouds, snow
and sea ice.
The advent of passive microwave sensors on NASA satellites, starting in 1973
with the Electrically Scanning Microwave Radiometer (ESMR), was significant in
providing the ability to monitor sea ice conditions throughout the polar night and in
the presence of cloud cover (which cannot be done with optical and infrared systems
like MODIS). ESMR was superseded by the Scanning Multichannel Microwave
Radiometer (SMMR) (launched in 1978), and with the launch of the DMSP F8 sat-
ellite in 1987, the first of the Special Sensor Microwave/Imager (SSM/I) series of
sensors. With the launch of DMSP F16, SSM/I superseded in 2005 by the Special
Sensor Microwave Imager/Sounder (SSMIS). The combined SMMR, SSM/I and
SSMIS records provide daily, continuously updated gridded fields of sea ice extent
and concentration spanning more than thirty years. The passive microwave data are
also used to assess surface melt over sea ice and ice sheets. Starting in 2002, the
Advanced Microwave Sounding Radiometer E (AMSR-E) aboard the NASA Aqua
satellite provided ice concentration data at a higher spatial resolution than SSM/I or
SSMIS. Although AMSR-E failed in 2011, the Japan Aerospace Exploration Agency
successfully launched the AMSR2 instrument in 2012. In the 1990s, European and
Japanese research satellites carried synthetic aperture (active) radar (SAR) sensors.
These provided high-resolution sea ice data, also with all-weather and polar dark-
ness capability. In November 1995, Canada launched Radarsat, giving routine cov-
erage of most of the Arctic.
From 2003 through 2009, NASA's Ice, Cloud and land Elevation Satellite
(ICESat), carrying a laser altimeter system with the ability to detect variations in
surface height, provided information on sea ice thickness and (through time changes
in height) ice sheet mass balance. ICESat-2, with advanced capabilities, is scheduled
for launch in early 2016. Operation IceBridge, a series of aircraft missions carrying
a suite of sensors, is spanning the gap between ICESat and ICESat-2. CryoSat-2,
