Variability of winter sea ice in Greenland-Iceland-Norwegian Sea

We study the variability of the marginal ice zone in Greenland-Iceland-Norwegian (GIN) Sea, where the commonly named Arctic Odden has been observed frequently in the last century, an ice tongue with large daily variability in size and shape. Affecting the heat and salinity budgets and thereby the dynamics of the underlying water masses, this ice tongue has a direct influence on the deep-ocean convection (Paluszkiewicz et al., 1994; Wadhams et al., 2002).

 

To simulate the Arctic Odden we force the regionally coupled atmosphere-ocean-sea ice modelMPIOM/REMO/HD (Sein et al. (2015), Elizalde (2011)) with the ERA-40 reanalysis dataset from the European Center for Medium-Range Weather Forecasts. Our experiment covers the time period 1958-2001. In contrast to most global climate models, this regional model is capable to realistically simulate the Arctic Odden in the marginal sea ice zone in GIN Sea. In our model and similar to observations, such an Odden persists from a few days to several months. The earliest appearance can be found in December and the latest in April, almost equally distributed within these months. An example of a typcial Odden ice tongue is given in Fig. 1.

 

The formation of the Arctic Odden can be caused either by eastward advection of sea ice or due to freezing of cold polar water, diverted eastward from the East Greenland current. Previous studies state that especially in early winter the Odden is a result of new ice formation associated with moderate westerly winds, bringing cold air from the Greeland Ice sheets (Shuchman et al., 1998; Comiso et al., 2001; Rogers and Hung, 2008) . Wadhams and Comiso (1999), however, define a second Odden type and show that especially in late spring, when the thermodynamic conditions do not permit new ice growth in that region, advection can drive the Odden formation.

 

We investigate several Odden events and find that, in contrast to observations, in our model Arctic Odden formation is driven by the advection of sea ice from the Greenland coast and from the main ice pack in GIN Sea, irrespective of the time when it occurs. To highlight the main mechanism behind the Odden formation within our model, an example is given in Fig. 2. While in the mean southward ice drift freezing is dominating, melting supports the Arctic Odden formation in the north-eastern marginal ice zone (Fig. 2, right panel). This leads, in some events more than in others, to the tongue shape of the Odden. The Odden itself (the south-eastern part of the ice edge) shows only small changes due to melting and freezing. However, freezing seems to strengthen the center of the southern shape of the Odden (north of Jan Mayen) in most of the events.

 

Within the coupled model, the Arctic Odden formation is coherent with a weak Icelandic low and a strong gyre circulation of sea ice in the Central Arctic. This indicates a linkage between large-scale Arctic sea ice variability and the appearance of such Odden. As previously suggested by e.g., Germe et al. (2011) , the marginal ice zone variability might be to some extent linked with large-scale processes, which impact the whole Arctic. However, regional atmospheric and oceanic forcing is also responsible for the Odden formation. Both, the large-scale atmospheric conditions as well as the small-scale processes in the atmosphere and in the ocean of the region of interest should be taken into account for further investigations of Odden formation.

 

Fig. 1: Sea ice concentration of one specic Arctic Odden event in January 1962 , at the beginning (left) and at the end (right). Change of sea ice thickness (difference of end and beginning, in m; middle). The geographical domain covers the region from 67° to 81° N and from 20° W to 8° E.

 

Fig. 2: Mean sea ice thickness change per day (left), divergence of sea ice transport and superimposed sea ice transport (middle) for the same Odden event as in Figure 1. The behavior of this specific event is coherent with other investigated Odden events. The residual term (right) includes oceanic and atmospheric fluxes that cause melting (negative values) and freezing (positive values).

 

More details can be found in Niederdrenk and Mikolajewicz (2016).

References:

Comiso, J. C., P. Wadhams, L. T. Pedersen, and R. A. Gersten (2001), Seasonal and interannual variability of the Odden ice tongue and a study of environmental effects, J. Geophys. Res., 106(C5), 9093–9116, doi:10.1029/2000JC000204 (link)

 

Elizalde Arellano A. (2011) The water cycle in the Mediterranean region and the impacts of climate change. Reports on Earth System Science (PhD thesis) (link)

 

Germe, A., M.-N. Houssais, C. Herbaut, and C. Cassou (2011), Greenland Sea sea ice variability over 1979–2007 and its link to the surface atmosphere, J. Geophys. Res., 116, C10034, doi:10.1029/2011JC006960 (link)

Rogers, J. C., and M.-P. Hung (2008), The Odden ice feature of the Greenland Sea and its association with atmospheric pressure, wind, and surface flux variability from reanalyses, Geophys. Res. Lett., 35, L08504, doi:10.1029/2007GL032938 (link)

Sein, D. V., U. Mikolajewicz, M. Gröger, I. Fast, W. Cabos, J. G. Pinto, S. Hagemann, T. Semmler, A. Izquierdo, and D. Jacob (2015). Regionally coupled atmosphere-ocean-sea ice- marine biogeochemistry model ROM: 1. description and validation, J. Adv. Model. Earth Syst., 7, 268-304, doi:10.1002/2014MS000357 (link)

Shuchman, R. A., E. G. Josberger, C. A. Russel, K. W. Fischer, O. M. Johannessen, J. Johannessen, and P. Gloersen (1998), Greenland Sea Odden sea ice feature: Intra-annual and interannual variability, J. Geophys. Res., 103(C6), 12709–12724, doi:10.1029/98JC00375 (link)

Wadhams, P., and J. C. Comiso (1999). Two modes of appearance of the Odden ice tongue in the Greenland Sea. Geophysical Research Letters , 26, 1999. doi:10.1029/1999GL900502 (link)