Variations in the Age of Arctic Sea-ice and Summer Sea-ice Extent
Ignatius G. Rigor1,2 & John M.
Center, Applied Physics Laboratory, University of Washington
of Atmospheric Sciences, University
Geophys. Res. Lett., v. 31, doi:10.1029/2004GL019492, 2004. [Full
Three of the past six summers have exhibited record low sea-ice extent on the Arctic Ocean. These minima may have been dynamically
induced by changes in the surface winds. Based on results of a simple model
that keeps track of the age of ice as it moves about on the Arctic
Ocean, we argue that the areal coverage of thick multi-year ice
decreased precipitously during 1989-1990 when the Arctic Oscillation was in an
extreme “high index” state, and has remained low since that time. Under these
conditions, younger, thinner ice anomalies recirculate back to the Alaskan
coast more quickly, decreasing the time that new ice has to ridge and thicken
before returning for another melt season. During the 2002 and 2003 summers this
anomalously younger, thinner ice was advected into Alaskan coastal waters where
extensive melting was observed, even though temperatures were locally colder
than normal. The age of sea-ice explains more than half of the variance in
summer sea-ice extent.
1. Age of
sea ice on the Arctic Ocean estimated from the
drift of buoys
(pink tracks), and satellite derived estimates of sea ice extent
(green line). Some things to note:
Changes in wind and ice motion related to the Arctic Oscillation drives
changes in the age and thickness of sea ice.
Area of old ice has decreased dramatically during the last 15 years.
Recirculation of younger, thinner sea ice back to the Alaskan coast
explain most of the variance in summer sea ice extent.
This relationship may be exploited to predict summer sea ice extent.
Animations of the age of sea ice updated through October 2007:
MPG movie showing buoy drift and ice concentrations.
MPG format showing buoy drift (no ice concentrations).
The red dots shows the current location of buoys used to estimate the age of
sea ice. The areas of older, thicker ice are shown in white, while younger,
thinner sea ice is shown as darker shades of blue.
This animation of the age of sea ice shows:
1.) A large Beaufort Gyre which covers most of the Arctic Ocean during the 1980’s, and a transpolar drift
stream shifted towards the Eurasian Arctic. Older, thicker sea ice (white ice)
covers about 80% of the Arctic Ocean up to
1988. The date is shown in the upper left corner.
2.) With the step to high-AO conditions in 1989, the
Beaufort Gyre shrinks and is confined to the corner between Alaska
The Transpolar Drift Stream now sweeps across most of the Arctic Ocean,
carrying most of the older, thicker sea ice out of the Arctic Ocean through
Fram Strait (lower right). By 1990, only about 30% of the Arctic
Ocean is covered by older thicker sea ice.
3.) During the high-AO years that follow (1991 and on),
this younger thinner sea ice is shown to recirculated back to the Alaskan coast
where extensive open water has been observed during summer.
age of sea ice drifting towards the coast explains over 50% of the variance in
summer sea ice extent (compared to less than 15% of the variance explained by
the seasonal redistribution of sea ice, and advection of heat by summer winds).
was funded by a fellowship from the Applied Physics Laboratory, University of Washington, by NOAA Grant NA17RJ1232,
and ONR Grant N00014-98-1-0698. Wallace was funded by the National Science
Foundation under grant ATM 0318675. This publication was partially funded by
the Joint Institute for the Study of the Atmosphere and Ocean (JISAO) under
NOAA Cooperative Agreement No. NA17RJ1232, Contribution # 1054.
References and notes: