Greenland Sea sea ice variability over 1979-2007 and its link to the surface atmosphere
Résumé
Mean winter Arctic sea ice concentration based on passive microwave observations for the period 1979-2007 are analyzed to examine the variability of the western Nordic Seas marginal ice zone (MIZ). A principal component analysis performed on this regional domain shows that the interannual variability is dominated by a mode which captures more than 70% of the total variance and shows only moderate correlation with the leading mode of global Northern Hemisphere sea ice variability. This mode appears to be related to a pattern of sea level pressure (SLP) anomaly centered on the MIZ with large scale signature resembling the canonical pattern of the North Atlantic Oscillation (NAO). Still this leading mode of SIC variability shows a weak temporal correlation with the NAO index. Taking into account the intrinsic spatial asymmetry found between the two phases of the NAO based on a weather regimes analysis, composite SIC fields are constructed which indeed suggest a preferential response of the Greenland Sea SIC variability to negative NAO-like patterns of SLP. The SLP pattern is consistent with a response of the sea ice margin to the strength of the northerly winds along eastern Greenland. A weak pattern of surface air temperature anomalies also emerges in the central Greenland Sea which occurs, at least partly, as a response of the surface atmosphere to sea ice concentrations changes. Higher order modes of winter SIC variability emerge based on a shorter winter season. One mode has much resemblance with the Odden/Nordbukta pattern while another one exhibits a significant signature in the center of the Greenland Sea convective gyre. The Odden/Nordbukta mode shows a more symmetric relation to the NAO than the leading SIC mode. Linear regression analysis consistently suggests some link between this mode and the ice area flux through Fram Strait.
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