Publication Date:
2011-02-01
Description:
Strontium isotopic composition (87Sr/86Sr) data from subfossil 14C-dated mollusk shells in raised beach sediments are used as a paleosalinity proxy in the brackish Baltic Sea, the precision ({+/-}5%) and accuracy ({+/-}0.7{per thousand}) of the method being judged from replicate analyses of modern shells. Paleosalinity data with an average time resolution of [~]200 yr for the period 7130-2775 calibrated 14C yr B.P. indicate maximum surface salinities of 10{per thousand}-11{per thousand}, 11{per thousand}-12{per thousand}, and 12{per thousand}-13{per thousand} for the Bothnian Bay, Bothnian Sea, and Baltic Proper (the three major Baltic subbasins). The relative salinity differences between the basins were small ([≤]30%) compared to the as much as eightfold present-day relative salinity differences (Bothnian Bay 1{per thousand}-3{per thousand}; Bothnian Sea 4{per thousand}-5{per thousand}; Baltic Proper 6{per thousand}-8{per thousand}). Late Holocene freshening (ca. 3000 calibrated 14C yr B.P. to present) is most pronounced in the northernmost subbasin, the Bothnian Bay, consistent with the absence of a permanent halocline, sequestering of phosphorus in well-oxygenated bottom sediments, and phosphorus limitation of primary production in the present-day Bothnian Bay. This study suggests that paleosalinity data may be crucial to improving our understanding of the possible effects of any future, climate-induced freshening of the Baltic Sea.
Print ISSN:
0091-7613
Electronic ISSN:
1943-2682
Topics:
Geosciences
Permalink
