There has been considerable interest in the recent state of Arctic sea ice
for scientific research and for operational applications especially along
the Northern Sea Route and the Northwest Passage. This pair of sea ice
maps was derived from radar data from NASA's QuikScat satellite
scatterometer on September 2, 2008 (left panel) and September 5, 2008
(right panel).
QuikScat's unique features make it a powerful tool for mapping sea ice and
accurately identifying sea ice conditions. It can distinguish sea ice from
open water, differentiate different classes of ice, and compensate for
effects of strong winds on ocean surfaces and effects of melt on ice.
In the above images, red areas denote sea ice that was undergoing active
melting on the ice surface, magenta areas show sea ice with reduced melt,
cyan areas are refrozen sea ice that had some residual wetness from
earlier melting, and white areas represent sea ice that had been refrozen
for 10 or more days. Ocean areas with less than 15 percent ice cover on
the surface are blue, while land surfaces are shown in brown and missing
data are depicted in black.
Along the coast of Siberia, the Northern Sea Route was blocked by ice in
an area northeast of Taymyr Peninsula (denoted by the black "T") on
September 2. Just three days later, on September 5, an ocean path was
observed in the same area. Warm air transported by northward winds led to
extensive areas of active melt (red) over a larger region extending from
the Barents Sea across the Kara Sea to the Laptev Sea on September 5. That
melt event was so large that some parts of it reached as far north as the
vicinity of the North Pole.
Along the Canadian north coast, the Northwest Passage was blocked in the
Parry Channel north of Victoria Island (denoted by the black "V") on both
of these dates, and ice in the small straits south of Victoria Island was
slightly reduced on September 5 compared to that on September 2. Very
little active melt (red) was observed in the Canadian Arctic Archipelago
on both dates.
The sea routes may be opened or closed rapidly by transient weather
events. Such unstable sea ice conditions in the passages can cause a
significant navigation risk.
The total sea ice extent in the Arctic at this time was about 0.5 million
square kilometers (0.2 mission square miles) larger than that at the same
time last year. That difference in sea ice extent amounts to an area the
size of Spain.
QuikSCAT, managed by JPL, measures ocean surface wind/stress by sending
radar pulses to the surface and measuring the strength of the signals
returned.
QuikScat Background
NASA's Quick Scatterometer (QuikScat) spacecraft was launched from
Vandenberg Air Force Base, California on June 19, 1999. QuikScat carries
the SeaWinds scatterometer, a specialized microwave radar that measures
near-surface wind speed and direction under all weather and cloud
conditions over the Earth's oceans. More information about the QuikScat
mission and observations is available at http://winds.jpl.nasa.gov/missions/quikscat/.
QuikScat is managed for NASA's Science Mission Directorate, Washington,
DC, by NASA's Jet Propulsion Laboratory, Pasadena, CA.