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Long-term characteristics of simulated ice deformation in the Baltic Sea (1962–2007)
Swedish Meteorological and Hydrological Institute (SMHI), Norrköping, Sweden.
Swedish Meteorological and Hydrological Institute (SMHI), Norrköping, Sweden.
Swedish Meteorological and Hydrological Institute (SMHI), Norrköping, Sweden.
Swedish Meteorological and Hydrological Institute (SMHI), Norrköping, Sweden.
2013 (English)In: Journal of Geophysical Research - Oceans, ISSN 2169-9291, Vol. 118, no 2, 801-815 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2013. Vol. 118, no 2, 801-815 p.
National Category
Oceanography, Hydrology, Water Resources
Research subject
Oceanography
Identifiers
URN: urn:nbn:se:su:diva-93964DOI: 10.1002/jgrc.20089ISI: 000317840700017OAI: oai:DiVA.org:su-93964DiVA: diva2:650410
Note

Authorcount: 4;

Available from: 2013-09-20 Created: 2013-09-20 Last updated: 2014-12-03Bibliographically approved
In thesis
1. Ridged sea ice modelling in climate applications
Open this publication in new window or tab >>Ridged sea ice modelling in climate applications
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This work aims to increase our understanding of the nature of large scale features of sea ice from a dynamics point of view.Sea ice plays an important part in the exchange of heat and humidity between sea and air and thus is an important component of the climate system. Its physical presence also directly impacts the various forms of life such as diatoms, polar bears and humans alike.The dynamics of sea ice affect both weather and climate, through the large scale drift in the Arctic from the Siberian coast towards Fram Strait, through creation of cracks in the ice called leads or polynyas, and through ridging and other mechanical deformations of ice floes.In this work, we have focused on modelling of ridged ice for a number of reasons. Direct observations of the internal ice state is very difficult to perform and in general, observations of sea ice are either sparse or of limited information density. Ridged ice can be seen as the memory of high ice stress events, giving us a view on these highly dynamic events. Ridging is of major importance for the ice thickness distribution, as the thickest ice can only be formed through mechanical processes. Further, ridged ice is of direct interest for anyone conducting shipping through seasonal or perennial ice covered seas as it can form impenetrable barriers or in extreme even cases crush a ship caught within the ice pack.

To this end, a multi-category sea ice model, the HELsinki Multi category Ice model (HELMI), was implemented into the Rossby Centre Ocean model (RCO). HELMI has explicit formulations for ridged and rafted ice, as well as sub-grid scale ice thickness distribution (a feature shared with other multi category models) and an ice strength based on energetics. These features give RCO better representation of sub-grid scale physics and gives us the possibility to study the deformed ice in detail.

In paper I we look at the change in behaviour in the Arctic as the ice becomes more mobile, leading to a slight increase in modelled ridged ice volume in the central Arctic, despite a general trend of a decreasing ice cover.Paper II takes us to the Baltic Sea and the possibilities of modelling ridge ice concentration with a statistical model.In Paper III we investigate how the diminishing ice cover in future scenarios affects the biological activity in the Baltic Sea.Finally Paper IV investigates how the ice stress and the internal ice force can be interpreted in terms of ice compression on the ship scale.

Place, publisher, year, edition, pages
Department of Meteorology, Stockholm University, 2013. 37 p.
Keyword
Arctic ocean, Baltic Sea, sea ice, ice dynamics, numerical modelling, climate, ice deformation, ice compression, physical and biogeochemical interactions
National Category
Oceanography, Hydrology, Water Resources
Research subject
Atmospheric Sciences and Oceanography
Identifiers
urn:nbn:se:su:diva-93977 (URN)978-91-7447-767-2 (ISBN)
Public defence
2013-10-22, William-Olssonsalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defence the following paper was unpublished and had a status as follows: Paper 4: Manuscript

Available from: 2013-09-30 Created: 2013-09-22 Last updated: 2013-09-25Bibliographically approved

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