The last two millennia: climate, ocean circulation and paleoproductivity inferred from planktic foraminifera, south-western Svalbard margin

Abstract

We reconstruct climate and changes in water-mass properties in relation to variations in palaeoproductivity at the south-western Svalbard margin throughout the last 2000 years. Environmental conditions in subsurface (ca. 250–75 m) and near-surface to surface water (75–0 m) were studied on the basis of the distribution patterns and fluxes of planktic foraminiferal faunas. Stable isotopes in three different species were measured, and Mg/Ca- and transfer function-based sea-surface temperatures were calculated. The mean shell weights of planktic foraminiferal species were used to assess changes in calcium carbonate preservation. Modern total planktic foraminiferal distribution patterns from plankton tows and the water column carbonate chemistry were investigated for comparison with the palaeo-data. The results show warm sea-surface conditions and moderate to high surface productivity at ca. 21–400 AD, ca. 900–1400 AD and from about 1850 AD until present, which may be local expressions of the European climatic events known as the Roman Warm Period, the Medieval Climate Anomaly and the Recent Warming. In general, cold near-sea-surface conditions and very low to moderate average productivity occurred at about 400–900 AD and ca. 1400–1850 AD, the latter probably the local expression of the Little Ice Age. The highest and most variable planktic productivity occurred at ca. 1300–1500 AD, ca. 1750–1860 AD and during the last 50 years or so. These periods are linked to the general amelioration of conditions from years with a dense sea-ice cover to years with a rapidly fluctuating summer sea-ice margin