Atlantic Water advection versus sea‐ice advances in the eastern Fram Strait during the last 9 ka: Multiproxy evidence for a two‐phase Holocene

Abstract

[1] A sediment core from the West Spitsbergen continental margin was studied to reconstruct climate and paleoceanographic variability during the last~9 ka in the eastern Fram Strait (FS). Our multiproxy evidence suggests that the establishment of the modern oceanographic configuration in the eastern FS occurred stepwise, in response to the postglacial sea-level rise and the related onset of modern sea-ice production on the shallow Siberian shelves. The late Early and Mid-Holocene interval (9 to 5 ka) was generally characterized by relatively unstable conditions. High abundance of the subpolar planktic foraminifer species Turborotalita quinqueloba implies strong intensity of Atlantic Water (AW) inflow with high productivity and/or high AW temperatures, resulting in a strong heat flux to the Arctic. A series of short-lived cooling events (8.2, 6.9, and 6.1 ka) occurred superimposed on the warm late Early to Mid-Holocene conditions. Our proxy data imply that simultaneous to the complete postglacial flooding of Arctic shallow shelves and the initiation of modern sea-ice production, strong advance of polar waters initiated modern oceanographic conditions in the eastern FS at~5.2 ka. The Late Holocene was marked by the dominance of the polar planktic foraminifer species Neogloboquadrina pachyderma, a significant expansion of sea ice/ icebergs, and strong stratification of the water column. Although planktic foraminiferal assemblages as well as sea subsurface temperatures suggest a return of slightly strengthened advection of subsurface AW after 3 ka, a relatively stable cold-water layer prevailed at the sea surface, and the study site was probably located within the seasonally fluctuating marginal ice zone during the Neoglacial period.Citation: Werner, K., R. F. Spielhagen, D. Bauch, H. C. Hass, and E. Kandiano (2013), Atlantic Water advection versus sea-ice advances in the eastern Fram Strait during the last 9 ka: Multiproxy evidence for a two-phase Holocene, Paleoceanography, 28,[283][284][285][286][287][288][289][290][291][292][293][294][295]

Middle to late Holocene paleoproductivity reconstructions for the western Barents Sea: a model-data comparison

“…This inference is supported by a sea surface temperature reconstruction from the western Barents Sea margin indicating the absence of sea ice between 3000 and 1600 years BP [52]. Furthermore, it fits well with the continuous presence of the subpolar planktic foraminifer species Turborotalita quinqueloba off western Svalbard during the past 3000 years BP [74] suggesting persistent influence of Atlantic-derived water masses along the western Barents Sea margin and consequently limited southward extension of the MIZ. However, PP rates in PSh-5159N and R87 show a slight increase towards the end of the time period, between 1900 and 1500 years BP.…”

“…Frequent episodes of sediment entrainment and release during sea ice freezing and melting processes may have stimulated phytoplankton growth and potentially increased the export towards the seabed during the last 1000 years BP. The repeated shifts of warmer and colder conditions due to variable influence of AW/ArW in Storfjorden [43,44] and along the western Svalbard margin [73,74] are not recorded in our northernmost PP record. A likely reason for this observation could be the formation of coastal polynyas, which have been frequently observed in Storfjorden during the last decade [15,58].…”

“…1000 years BP [10]. This contrasts conditions further north, off the western Svalbard coast, where sea ice remained largely predominant in surface waters until the last century [38,63,73,74]. The persistent influence of AW at the MIZ from ca.…”

“…The latter suggests the presence of sea ice in the northern Barents Sea during the middle Holocene. This gradual cooling trend is observed all over the Nordic seas including the Barents Sea [1,16,23,61,74]. One reason for the increasing sea ice coverage during the middle Holocene might be the coupling between decreasing summer irradiance at high northern latitudes [30] and amplifying positive feedbacks such as the complete flooding of the Arctic shelves and established modern sea-ice production/export in the Arctic Ocean [3,74].…”

“…Under present day conditions the variable MIZ is the main controlling factor for both in situ production and export of marine organic matter as well as release of TOM in the northern Barents Sea [29]. Reconstructions of the sea ice margin in the broader study region for this time period [38,74], show a gradual southward expansion and increased influence of ArW in the Barents Sea (e.g. [16]).…”