Abstract
Abstract. We examine the simulated Arctic sea ice drift speed for the period 2003–2014 in the coupled Arctic regional climate model HIRHAM–NAOSIM 2.0. In particular, we evaluate the dependency of the drift speed on the near-surface wind speed and sea ice conditions. Considering the seasonal cycle of the Arctic basin averaged drift speed, the model reproduces the summer–autumn drift speed well but significantly overestimates the winter–spring drift speed, compared to satellite-derived observations. Also, the model does not capture the observed seasonal phase lag between drift and wind speed, but the simulated drift speed is more in phase with the near-surface wind. The model calculates a realistic negative correlation between drift speed and ice thickness and between drift speed and ice concentration during summer–autumn when the ice concentration is relatively low, but the correlation is weaker than observed. A daily grid-scale diagnostic indicates that the model reproduces the observed positive correlation between drift and wind speed. The strongest impact of wind changes on drift speed occurs for high and moderate wind speeds, with a low impact for rather calm conditions. The correlation under low-wind conditions is overestimated in the simulations compared to observation/reanalysis data. A sensitivity experiment demonstrates the significant effects of sea ice form drag from floe edges included by an improved parameterization of the transfer coefficients for momentum and heat over sea ice. However, this does not improve the agreement of the modeled drift speed / wind speed ratio with observations based on reanalysis data for wind and remote sensing data for sea ice drift. An improvement might be achieved by tuning parameters that are not well established by observations.
Highlights
Arctic sea ice has experienced a rapid decrease in recent decades (e.g., Serreze and Stroeve, 2015; Stroeve et al, 2012)
SID increases with decreasing sea ice concentration (SIC) when SIC is larger than ca. 30 %
We evaluated the sea ice drift speed (SID) and its dependency on the near-surface wind and the sea ice conditions on the multiyear, Arctic-wide mean scale during 2003–2014
Summary
Arctic sea ice has experienced a rapid decrease in recent decades (e.g., Serreze and Stroeve, 2015; Stroeve et al, 2012). Dynamical processes, such as a changed sea ice drift in response to changing wind, ocean currents, and sea ice conditions (e.g., reduction of sea ice concentration and thickness), play an important role in the redistribution of sea ice (Rampal et al, 2011; Serreze et al, 2007; Spreen et al, 2011). Except for the fast-ice and shear zones, sea ice moves largely in response to local winds and ocean currents. For compact sea ice in the inner Arctic or sea ice near the coasts, the internal friction can be as large as the forces due to the winds
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