2014-2015 THE WINTER OF OUR DISCONTENT Now is the winter of our discontent, made glorious summer by this sun of York A WINTER THAT IS Deformed, unfinished, sent before his time into this breathing world, scarce half made up......OR OF THE DIPOLE ANOMALY ON SEA ICE ....THE RISE AND FALL OF THE FRIGEAN EMPIRE During the positive/negative AO (i.e., Arctic SLPhasanegative/positive anomaly),a cyclonic/ anticyclonic wind anomaly occurs, indicating a sea ice divergence/convergence. The divergence (anomalous cyclo- nic circulation) of sea ice leads to anomalous ice export, while the convergence results in retention of sea ice inside the Arctic Ocean [ Wu IS DOCTOR et DR WHO OR DR. WU? The question is: Is the AO or the DA dynamically more important in terms of ice advection?

The dipole anomaly corresponds to the second-leading mode of EOF of monthly mean sea level pressure (SLP) north of 70°N during the winter season (October–March) and accounts for 13% of the variance. One of its two anomalous centers is stably occupied between the Kara Sea and Laptev Sea; the other is situated from the Canadian Archipelago through Greenland extending southeastward to the Nordic seas. The dipole anomaly differs from one described in other papers that can be attributed to an eastward shift of the center of action of the North Atlantic Oscillation. The finding shows that the dipole anomaly also differs from the “Barents Oscillation” revealed in a study by Skeie. Since the dipole anomaly shows a strong meridionality, it becomes an important mechanism to drive both anomalous sea ice exports out of the Arctic Basin and cold air outbreaks into the Barents Sea, the Nordic seas, and northern Europe.

When the dipole anomaly remains in its positive phase, that is, negative SLP anomalies appear between the Kara Sea and the Laptev Sea with concurrent positive SLP over from the Canadian Archipelago extending southeastward to Greenland, there are large-scale changes in the intensity and character of sea ice transport in the Arctic basin. The significant changes include a weakening of the Beaufort gyre, an increase in sea ice export out of the Arctic basin through Fram Strait and the northern Barents Sea, and enhanced sea ice import from the Laptev Sea and the East Siberian Sea into the Arctic basin. Consequently, more sea ice appears in the Greenland and the Barents Seas during the positive phase of the dipole anomaly. During the negative phase of the dipole anomaly, SLP anomalies show an opposite scenario in the Arctic Ocean and its marginal seas when compared to the positive phase, with the center of negative SLP anomalies over the Nordic seas. Correspondingly, sea ice exports decrease from the Arctic basin flowing into the Nordic seas and the northern Barents Sea because of the strengthened Beaufort gyre.

The finding indicates that influences of the dipole anomaly on winter sea ice motion are greater than that of the winter AO, particularly in the central Arctic basin and northward to Fram Strait, implying that effects of the dipole anomaly on sea ice export out of the Arctic basin become robust. The dipole anomaly is closely related to atmosphere–ice–ocean interactions that influence the Barents Sea sector.

Received: April 5, 2004; Final Form: August 14, 2005

Corresponding author address: Bingyi Wu, Chinese Academy of Meteorological Sciences

 The latest value: 6,641,095 km² (October 14, 2014)  

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