15 JULY 2004
Another Record Minimum for Sea Ice Cover in
the Arctic Ocean?
By Walt Meier, Florence Fetterer, and Nancy Geiger-Wooten
Is the Arctic in for another record low sea ice year? It is starting to look
like it. The recently released June 2004 ice extent and concentration are much
lower than normal (Fig. 1-3), indicating that annual minimum
ice extent, which occurs in September, is likely to be well
If so, this would be the third year in a row with substantial below-normal
ice conditions in the Arctic, an unprecedented event in the 30+ year record
satellite observations of Arctic sea ice.
Figure 1: Monthly average total sea ice
extent anomaly for the month of June 2004, which is ~5% lower than the
1988-2000 mean. Sea ice extent
here as all pixels with a >15% sea ice concentration.
Figure 2: Sea ice extent field for June 2004. The magenta contour is
the 1988-2000 mean extent.
Figure 3: Sea ice concentration anomaly field for June 2004. Near the
ice edge, many of the dark blue negative anomalies correspond to regions
any ice in June 2004.
After a record minimum sea ice extent in September 2002, followed by a September
2003 extreme that was nearly as low, early indications are that 2004 will
be a very low ice year. May 2004 extent was poleward of the mean extent
in virtually all regions of the Arctic (see NSIDC's Sea
Ice Index for images).
This indicates that ice began melting faster than normal; however, May
necessarily indicative of conditions at the
end of the melt season in September. The correlation between concentration
anomalies (Fig. 4) in May and September is low (0.34);
however, correlation with June anomalies is much more significant (0.71).
Thus, the below normal
June extent (Fig. 1, 2) and large negative concentration
3) are suggestive that the Arctic may be in for a third low ice year in
Figure 4: Correlation of May through August monthly mean sea ice extent
anomalies with September sea ice extent anomaly.
Such low concentrations may be indicative of climate change. While there
is substantial interannual variability in the summer minimum ice extent,
record has revealed a significant downward trend of ~9% per decade (e.g.,
Comiso, 2002) in the summer minimum extent, which corresponds to ~300,000 km 2
per decade (e.g., Cavalieri et al., 2003). This trend could have substantial
ramifications for the Arctic region in terms of commerce, wildlife, and the
human population and may be a harbinger of large-scale global changes.
trends continue, the Arctic may be completely free of ice during at least
some of the summer by 2050 (e.g., Flato and Boer, 2001; Johannessen et
Caution should be used in interpreting a three-year sequence of much-below
average ice extents; however, if September 2004 ice extent does approach
that of 2002 and 2003, it would be an unprecedented event and perhaps
that “possibility” may soon be turning into “reality.”
The monthly images are produced as part of NSIDC's Sea
Monthly mean sea ice concentrations are
produced at NSIDC from DMSP Special Sensor Microwave/Imager (SSM/I) data.
The 1979-2002 time series used
to determine correlations were calculated from Nimbus-7 Scanning Multichannel
Microwave Radiometer (SMMR) and
D.J., C.L. Parkinson, K.Y. Vinnikov, 30-year satellite record reveals
contrasting Arctic and Antarctic decadal sea ice variability, Geophys.
Lett., 30(18), 1970, doi: 10.1029/2003GL018031, 2003.
A rapidly declining perennial sea ice cover in the Arctic, Geophysical Research Letters,
29(20), 1956, doi: 10.1029/2002GL015650, 2002.
Flato, G.M., and G.J. Boer, Warming asymmetry in climate change simulations,
Geophysical Research Letters, 28(1), 195-198, 2001.
Johannessen, O.L., E.V. Shalina, and M.W. Miles, Satellite evidence
for an Arctic sea ice cover in transformation, Science, 286, 1937-1939,
Arctic Sea Ice News & Analysis
Sea Ice Index