Long‐term characteristics of simulated ice deformation in the Baltic Sea (1962–2007). Issue 2 (13th February 2013)

• Record Type: Journal Article
• Authors: Löptien, U.; Mårtensson, S.; Meier, H.E.M.; Höglund, A.
• Is Part Of: Journal of geophysical research. Volume 118:Issue 2(2013:Feb.)
• Page Start: 801
• Page End: 815
• Publication Date: 2013-02-13
• Subjects: Baltic Sea -- sea ice -- ice deformation -- ridges -- climate -- NAO; Oceanography -- Periodicals; 551.4605
• DOI: 10.1002/jgrc.20089
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract : [1] The North Atlantic Oscillation (NAO) index is a frequently used measure for the mean winter conditions in Northern Europe. A positive, high index is associated with strong westerlies and anomalous warm temperatures. The effects on sea ice conditions in the Baltic Sea are twofold. Warm temperatures prevent sea ice formation. If ice is present nevertheless, the strong winds can promote the formation of ice ridges which hinders ship traffic. We use an ocean‐sea ice model to investigate the NAO impact on the ridged ice area fraction in the Baltic during 1962–2007. Our simulations indicate that in the northern Bothnian Bay, a high NAO index is related to an anomalous accumulation of ridges, while in the rest of the Baltic Sea, the relationship is contrary. The NAO explains locally at most only 20–25% of the ridged ice fraction interannual variability which indicates the systems complexity. However, we find high skill with local correlations around 0.8 for annually averaged ridged ice fraction reconstructed from multilinear regression using winter averaged wind extremes, surface air temperature, and sea surface temperature (SST). This suggests that the amount of ridged ice in late winter can be derived from these routinely measured quantities. In large parts of the basin, it is sufficient to use the atmospheric parameters as a predictor, while in the eastern Bothnian Bay and southern Gulf of Finland, the SST is required to reconstruct the bulk of the ridged ice fraction. Key Points: Hindcast for the Baltic Sea including ridged ice (1962‐2007). The NAO is a poor predictor to explain ridging in the Baltic Sea. High predictive skill of seasonal wind extremes (N, S, E, W), air temp. and SST.