Bathymetric properties of the Baltic Sea

Jakobsson, Martin1, Stranne, Christian1, O'Regan, Matt1, Greenwood, Sarah L.1, Gustafsson, Bo2, Humborg, Christoph2, and weidner, Elizabeth1,3

1Department of Geological Sciences, Stockholm University, Stockholm, 10691, Sweden

2The Baltic Sea Centre, Stockholm University, Stockholm, 10691, Sweden

3Department of Earth Science, University of New Hampshire, 56 College Road, Durham, NH, USA

Abstract
Baltic Sea bathymetric properties are anal-ysed here using the newly released digital bathymetricmodel (DBM) by the European Marine Observation and DataNetwork (EMODnet). The analyses include hypsometry, vol-ume, descriptive depth statistics, and kilometre-scale seafloorruggedness, i.e. terrain heterogeneity, for the Baltic Sea as awhole as well as for 17 sub-basins defined by the Baltic Ma-rine Environment Protection Commission (HELCOM). Wecompare the new EMODnet DBM with IOWTOPO the pre-viously most widely used DBM of the Baltic Se aproducedby the Leibniz-Institut für Ostseeforschung Warnemünde(IOW), which has served as the primary gridded bathymetricresource in physical and environmental studies for nearly twodecades. The area of deep water exchange between the Both-nian Sea and the Northern Baltic Proper across the ÅlandSea is specifically analysed in terms of depths and loca-tions of critical bathymetric sills. The EMODnet DBM pro-vides a bathymetric sill depth of 88 m at the northern sideof the Åland Sea and 60 m at the southern side, differingfrom previously identified sill depths of 100 and 70 m, re-spectively. High-resolution multibeam bathymetry acquiredfrom this deep water exchange path, where vigorous bottomcurrents interacted with the seafloor, allows us to assess whatpresently available DBMs are missing in terms of physicalcharacterization of the seafloor. Our study highlights the needfor continued work towards complete high-resolution map-ping of the Baltic Sea seafloor

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