Deglacial and Holocene conditions in northernmost Baffin Bay: sediments, foraminifera, diatoms and stable isotopes

Abstract

A multiproxy study of palaeoceanographic and climatic changes in northernmost Baffin Bay shows that major environmental changes have occurred since the deglaciation of the area at about 12 500 cal. yr BP. The interpretation is based on sedimentology, benthic and planktonic foraminifera and their isotopic composition, as well as diatom assemblages in the sedimentary records at two core sites, one located in the deeper central part of northernmost Baffin Bay and one in a separate trough closer to the Greenland coast. A revised chronology for the two records is established on the basis of 15 previously published AMS 14 C age determinations. A basal diamicton is overlain by laminated, fossil-free sediments. Our data from the early part of the fossiliferous record (12 300-11 300 cal. yr BP), which is also initially laminated, indicate extensive seasonal sea-ice cover and brine release. There is indication of a cooling event between 11 300 and 10 900 cal. yr BP, and maximum Atlantic Water influence occurred between 10 900 and 8200 cal. yr BP (no sediment recovery between 8200 and 7300 cal. yr BP). A gradual, but fluctuating, increase in sea-ice cover is seen after 7300 cal. yr BP. Sea-ice diatoms were particularly abundant in the central part of northernmost Baffin Bay, presumably due to the inflow of Polar waters from the Arctic Ocean, and less sea ice occurred at the near-coastal site, which was under continuous influence of the West Greenland Current. Our data from the deep, central part show a fluctuating degree of upwelling after c. 7300 cal. yr BP, culminating between 4000 and 3050 cal. yr BP. There was a gradual increase in the influence of cold bottom waters from the Arctic Ocean after about 3050 cal. yr BP, when agglutinated foraminifera became abundant. A superimposed short-term change in the sea-surface proxies is correlated with the Little Ice Age cooling.

Benthic and planktic community changes at the North Siberian margin in response to Atlantic water mass variability since last deglacial times

“…This is because the occurrence of C. neoteretis at the Arctic continental margins is clearly restricted to the areas influenced by modified Atlantic waters, and seems to avoid regions with admixture of freshened shelf waters Wollenburg and Mackensen, 1998;Osterman et al, 1999;Lubinski et al, 2001;Wollenburg et al, 2004). This species has also been found to be related to areas of brine release from sea ice freezing at the surface (Knudsen et al, 2008), and to be common in seasonally ice-free conditions with high seasonal productivity . Food preferences of C. neoteretis, probably phytodetritus or associated bacteria, reflect an association with FSBW with relatively high phytodetrital deposition, temperature and salinity (Wollenburg and Mackensen, 1998;Lubinski et al, 2001).…”

“…High percentages of opportunistic species E. clavatum and cold-water Stainforthia loeblichi indicate heavy seasonal sea-ice conditions Ślubowska et al, 2005). An opportunistic species Stainforthia feylingi which reaches up to 20-30% gives evidence for unstable environment with periodically low oxygen conditions at the sea floor (Knudsen and Seidenkrantz, 1994;Knudsen et al, 2008). Arctic species I. norcrossi/helenae, I. islandica, and Cibicides lobatulus are characteristic of cold and saline water environment (Steinsund et al, 1994; Polyak et al, 2002).…”

“…and P. williamsoni. An exceptionally high spike of up to 80% of S. feylingi at 14.4 ka likely indicates reduced ventilation resulting from enhanced productivity (Knudsen et al, 2008). Subsurface ADW inflow was strong and constant as seen from the highest percentages of C. neoteretis.…”

Controls upon the Last Glacial Maximum deglaciation of the northern Uummannaq Ice Stream System, West Greenland

“…kyr BP (McCarthy, 2011). This initiation of the WGC onto the Uummannaq shelf is later than northwest Greenland and Baffin Bay (Levac et al, 2001, Knudsen et al, 2008. This maybe a partial result of excess meltwater flux from the GIS as it retreated from the outer shelf (McCarthy, 2011).…”

Interaction between subsurface ocean waters and calving of the Jakobshavn Isbræ during the late Holocene

“…6B). Greenland (Møller et al 2006;Seidenkrantz et al 2007;Ren et al, 2009) and the Nares Strait (Knudsen et al 2008) as well as from terrestrial studies from Baffin Island, NE Canada and West…”