Late Quaternary paleoceanography of the western Baffin Bay region: evidence from fossil diatoms

Abstract

Seven marine cores from the east coast of Baffin Island were examined for variations in diatom content. The cores have good age control and were used for Holocene paleoceanographic reconstruction. A diatom barren zone or a zone of much reduced diatom productivity is evident some time during the early to middle Holocene. This zone ends earlier in the southern area than farther north. The changes in diatom productivity may be caused by changing oceanographic variables such as sea ice extent and the presence of a meltwater cap during deglaciation. Light isotope 18O events ("meltwater spikes") generally coincide with barren or reduced productivity zones in the cores from the middle and southern part of the shelf and from Jones Sound, suggesting a general surficial cooling of the fjord and ocean water. If diatom productivity was depressed because of a meltwater cap over the core sites with increasing sea ice extent, the theory of a general "marine optimum" in all of Baffin Bay and Davis Strait from 8000 to 6000 BP may have to be modified.

A History of Sea Ice in the Canadian Arctic Archipelago Based on Postglacial Remains of the Bowhead Whale (<i>Balaena Mysticetus</i>)

“…The diatom record of a core (HU82-031-MC83.6) off McBeth Fiord, east central Baffin coast shows a generally high productivity for the interval 12.3 -8 ka B.P., interpreted as indicating seasonally open pack ice; however, the dating of this core (and others) is suspect, in that it utilized fine-grained total organic carbon (Williams, 1990). Williams reported other western Baffin Bay cores that penetrate 10 ka B.P.…”

“…We show here that bowhead whale subfossils (hereafter fossils) yield the best available proxy of sea-ice history. Some diatoms are known to have sea-ice affinity, but far too few marine sediment cores have been analyzed from the Arctic Archipelago to reconstruct regional sea-ice history by this means (see e.g., Williams, 1990;Short et al, 1994). Otherwise sea ice-excepting icebergs, which contain appreciable sediment loads (e.g., Ruddiman, 1987)-is a geological agent that leaves little or no coherent, direct record of its changing extent through time.…”

The Eastern Canadian Arctic at ca. 6 ka BP: A Time of Transition

“…Along the Baffin Island coast the diatom productivity hiatus (ca. 8-5.5 ka) has been interpreted as a signal of increased meltwater outflow over the coastal areas (Williams, 1990a). This probably was due to the very same conditions that warmed the land and this idea is supported by the increasing sediment accumulation rates recorded from the fjords around that same time (Fig.…”

“…However, the marine core record, based on eight cores, from the Baffin Island coast as discussed in Williams (1990a), from Strathcona Sound (Short et al, 1994) in the north and from Frobisher Bay in the south, suggests a different scenario. A time of initial glacial melt prior to 8 or 9 ka is often indicated by a spike in the diatom record, suggested by an enhanced flux of frustules to the sea floor.…”

“…Land-warming caused the glacial ice to melt increasingly rapidly, flushing out large quantities of fresh, cold (near freezing) meltwater. Meltwater may then have formed a cap of cold, relatively fresh water on top of the marine surface (Williams, 1990a), extending the sea ice season and limiting the time needed for algal growth. Further, the glacial meltwater may have been seasonally turbid, cutting down light transmission necessary for plant life.…”