caa a22 4500 475777387 CHVBK 20180406123634.0 cr unu---uuuuu 170329e20000101xx s 000 0 eng 10.1023/A:1002442212593 doi (NATIONALLICENCE)springer-10.1023/A:1002442212593 Atmospheric Response To Spatial Variations In Concentration And Size Of Polynyas In The Southern Ocean Sea-Ice Zone [Elektronische Daten] [R. Dare, B. Atkinson] Although it is well known that sea-ice regions are important components of the Earth's climate system, the exchanges of energy between ocean, ice and atmosphere are not well understood. The majority of past observational and modelling studies of atmosphere-surface interactions over sea-ice regions were primarily concerned with airflow over a single, isolated area of open water. The more realistic situations of multiple polynyas within a sea-ice field and different areal concentrations of sea ice were studied here. Spatial structure of the atmospheric boundary layer in response to this surface was simulated using a high-resolution numerical model. A sea-ice concentration of 80%, typical of the Southern Ocean sea-ice zone, was maintained within a 100-km wide domain. The effects of three polynya characteristics were assessed: their horizontal extent; local concentration of sea ice (LCI); and their arrangement with ice floes. Over polynyas of all sizes distinct plumes of upward heat flux, their width and height closely linked to polynya width, resulted in mixed layers 600 to 1000 m deep over and downwind of the polynyas, their depth increasing with polynya width. Mean surface heat flux (MSHF) increased with size in polynyas less than 30 km wide. The air-to-ice MSHF over the first 10 km of sea-ice downwind of each polynya and the domain-average surface heat flux increased linearly with polynya width. Turbulent kinetic energy plumes occurred over all polynyas, their heights and widths increasing with polynya widths. Downward flux of high momentum air in the plumes caused increased wind speeds over polynyas in the layer from about 300-1000 m above the surface, the depth varying directly with polynya width. MSHFs decreased as LCIs increased. The arrangement of polynyas had relatively little effect on the overall depth of the modified layer but did influence the magnitude and spatial structure of vertical heat transfer. In the two-polynya case the MSHF over the polynyas was larger when they were closer together. Although the MSHF over the sea ice between the polynyas decreased in magnitude as their separation increased, the percentage of the polynya-to-air heat recaptured by this ice floe increased fivefold. Kluwer Academic Publishers, 2000 Boundary layer nationallicence Numerical modelling nationallicence Sea ice nationallicence Multiple polynyas nationallicence Heat flux nationallicence Dare R. Department of Geography, Queen Mary and Westfield College, University of London, London, United Kingdom aut Atkinson B. Department of Geography, Queen Mary and Westfield College, University of London, London, United Kingdom aut Boundary-Layer Meteorology Kluwer Academic Publishers 94/1(2000-01-01), 65-88 0006-8314 94:1<65 2000 94 10546 https://doi.org/10.1023/A:1002442212593 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1023/A:1002442212593 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Dare R. Department of Geography, Queen Mary and Westfield College, University of London, London, United Kingdom aut NATIONALLICENCE 700 1- Atkinson B. Department of Geography, Queen Mary and Westfield College, University of London, London, United Kingdom aut NATIONALLICENCE 773 0- Boundary-Layer Meteorology Kluwer Academic Publishers 94/1(2000-01-01), 65-88 0006-8314 94:1<65 2000 94 10546 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer