Distinct Modes of Winter Arctic Sea Ice Motion and Their Associations with Surface Wind Variability |
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Authors: | WU Bingyi and Mark A JOHNSON |
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Institution: | Chinese Academy of Meteorological Sciences, Beijing 100081, Arctic Region Supercomputing Center, University of Alaska Fairbanks, Fairbanks, AK 99775, USA,Institute of Marine Science, University of Alaska Fairbanks, Fairbanks, AK 99775, USA |
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Abstract: | Using monthly mean sea ice velocity data obtained from the
International Arctic Buoy Programme (IABP) for the period of 1979--1998 and the
monthly mean NCEP/NCAR re-analysis dataset (1960--2002), we investigated the
spatiotemporal evolution of the leading sea ice motion mode (based on a complex
correlation matrix constructed of normalized sea ice motion velocity) and their
association with sea level pressure (SLP) and the predominant modes of surface
wind field variability. The results indicate that the leading winter sea ice
motion modes spatial evolution is characterized by two alternating and
distinct sea ice modes, or their linear combination. One mode (M1) shows a
nearly closed cyclonic or anti-cyclonic circulation anomaly in the Arctic Basin
and its marginal seas, resembling to a large extent the response of sea ice
motion to the Arctic Oscillation (AO), as many previous studies have revealed.
The other mode (M2) displays a coherent cyclonic or anti-cyclonic circulation
anomaly with its center close to the Laptev Sea, which has not been identified
in previous observational studies. In fact, M1 and M2 respectively reflect the
responses of sea ice motion to two predominant modes of winter surface wind
variability north of 70N, which well correspond, with slight
differences, to the first two modes of EOF analysis of winter monthly mean SLP
north of 70N. These slight differences in SLP anomalies lead to a
difference of M2 from the response of sea ice motion to the dipole anomaly.
Although the AO significantly influences sea ice motion, it is not crucial for
the existence of M1. The new sea ice motion mode (M2) has the largest variance
and clearly differs from the response of winter monthly mean sea ice motion to
the dipole anomaly in SLP fields, and corresponding SLP anomalies also show
differences compared to the dipole anomaly. This study indicates that in the
Arctic Basin and its marginal seas, slight differences in SLP anomaly patterns
can force distinctly different sea ice motion anomalies. |
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Keywords: | distinct mode Arctic sea ice motion Arctic surface wind forcing |
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