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The Associations of Arctic Sea Ice Drift with Atmospheric Circulation, and Their Implications for Arctic Sea Route

Author(s): Ruibo Lei

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Abstract: Seasonal and long-term changes in ice kinematics of the Arctic outflow region were quantified using 42 ice-tethered buoys deployed between 1979 and 2011. As ice drifted southward into the Fram Strait, the meridional ice speed increased dramatically, while associated zonal iceconvergence dominated the ice-field deformation. The Arctic atmospheric Dipole Anomaly (DA) influenced ice drift by accelerating the meridional ice velocity. Ice trajectories exhibited lessmeandering during the positive phase of DA and vice versa. From 2005 onwards, the buoy data exhibit high Arctic sea-ice outflow rates, closely related to persistent positive DA anomaly. However, the long-term data from 1979 to 2011 do not show any statistically significant trend for sea-ice outflow, but exhibit high year-to-year variability, associated with the change in the polarity of DA. Sea ice conditions in the Arctic Northeast Passage (NEP) have changeddramatically in the last four decades, with important impacts on the navigability. In OctoberNovember, spatially averaged ice thickness in the NEP decreased from 1.2-1.3 m in 2003-2006to 0.2-0.6 m in 2011-2012. From 1979 to 2012, the fastest decreasing trend in monthly iceconcentration occurred in October (-1.76% per year), when the ice cover starts to increase. As a result of decreasing multiyear sea ice, thinning ice and delayed freeze-up, the spatially averaged length of open period (ice concentration< 50%) increased from 84 days in the 1980s to 114 days in the 2000s and reached 146 days in 2012. The NEP East Siberian, Laptev, and Kara sectorswere relatively inaccessible. However, partly as a result of the thinning of sea ice prior to melting and enhanced positive polarity of summer DA, these sectors have become more accessible. Ahigh positive DA can load more sea ice from upstream into the Transpolar Drift Stream (TDS). High positive summer DA results in extended opening of sea routes, because the advected sea ice is not replaced by new ice. In contrast, in winter these regions are cold and refreezing of openwater is possible. Consequently, a high positive winter DA does not result in an extended summer opening. The statistical relationship between the Arctic Oscillation (AO) and theopening of the NEP was relative weakly, because the forcing of the AO on the sea ice export from the Russian coast is not direct.


Year: 2016

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