Reconstruction of Holocene oceanographic conditions in eastern Baffin Bay

Abstract

Abstract. Baffin Bay is a semi-enclosed basin connecting the Arctic Ocean and the western North Atlantic, thus making out a significant pathway for heat exchange. Here we reconstruct the alternating advection of relatively warmer and saline Atlantic waters versus the incursion of colder Arctic water masses entering Baffin Bay through the multiple gateways in the Canadian Arctic Archipelago and the Nares Strait during the Holocene. We carried out benthic foraminiferal assemblage analyses, X-ray fluorescence scanning, and radiocarbon dating of a 738 cm long marine sediment core retrieved from eastern Baffin Bay near Upernavik, Greenland (Core AMD14-204C; 987 m water depth). Results reveal that eastern Baffin Bay was subjected to several oceanographic changes during the last 9.2 kyr. Waning deglacial conditions with enhanced meltwater influxes and an extensive sea-ice cover prevailed in eastern Baffin Bay from 9.2 to 7.9 ka. A transition towards bottom water amelioration is recorded at 7.9 ka by increased advection of Atlantic water masses, encompassing the Holocene Thermal Maximum. A cold period with growing sea-ice cover at 6.7 ka interrupts the overall warm subsurface water conditions, promoted by a weaker northward flow of Atlantic waters. The onset of the neoglaciation at ca. 2.9 ka is marked by an abrupt transition towards a benthic fauna dominated by agglutinated species, likely in part explained by a reduction of the influx of Atlantic Water, allowing an increased influx of the cold, corrosive Baffin Bay Deep Water originating from the Arctic Ocean to enter Baffin Bay through the Nares Strait. These cold subsurface water conditions persisted throughout the Late Holocene, only interrupted by short-lived warmings superimposed on this cooling trend.

Evidence for influx of Atlantic water masses to the Labrador Sea during the Last Glacial Maximum

“…Radiocarbon measurements on benthic and planktic specimens at ~ 27,000 years ago show slightly younger ages for the benthic foraminifera (Seidenkrantz et al, 2019; Fig. 2) indicating that bottom-water conditions were well-ventilated within the entire depth range of the WGC, as previously also shown for the Holocene 40 . Shortly prior to the LGM, the number of these warmer Atlantic Water indicators decreased compared to earlier in MIS 2, becoming replaced with species indicating more chilled Atlantic Water, inferring a continued Atlantic Water influx, but with increased mixing of these waters with colder Polar Waters.…”

“…Core 479G itself does not encompass modern or Holocene deposits. However, at other sites along the West Greenland shelf from water depth corresponding to the present location of the core of the WGIW, the benthic foraminiferal assemblages today and during the Holocene are characterised by diverse faunas [38][39][40] , largely linked to the presence of chilled Atlantic Water (i.e., I. norcrossi) with comparatively low frequencies of the warmer, true Atlantic Water species [39][40][41] (for details on species groupings see Methods and Figs. 3 and 4).…”

Comparative analysis of six common foraminiferal species of the genera <i>Cassidulina</i>, <i>Paracassidulina</i>, and <i>Islandiella</i> from the Arctic–North Atlantic domain

“…This shallow infaunal species typically dwells in fine-grained sediments in regions influenced by cool, modified Atlantic Water (with relatively stable salinities and temperatures) across the Nordic Seas (e.g. Mackensen and Hald, 1988;Gooday and Lambshead, 1989;Jennings and Helgadóttir, 1994;Rytter et al, 2002;Jennings et al, 2004;Knudsen et al, 2012), the Labrador Sea and Baffin Bay (Holocene records: Seidenkrantz et al, 2013;Hansen et al, 2020), and into the Arctic Ocean and its marginal seas (Wollenburg and Mackensen, 1998;Husum et al, 2015;Jennings et al, 2020). It is noteworthy that in the eastern Nordic Seas it is also found in Atlantic-sourced water at deeper sites with cooler and more stable conditions than usual for C. laevigata (cf.…”

Holocene polynya dynamics and their interaction with oceanic heat transport in northernmost Baffin Bay

“…temperature and salinity). Based on previous foraminifera studies from the region 28 , 35 – 39 , two main groups were defined: the Polar/Arctic water group and the chilled Atlantic water group (Table 2 ). The Polar/Arctic water group consists of agglutinated cold water species such as Cuneata arctica and Textularia torquata and the calcareous species Elphidium clavatum .…”

“…The Polar/Arctic water group consists of agglutinated cold water species such as Cuneata arctica and Textularia torquata and the calcareous species Elphidium clavatum . The Atlantic water group consists of the calcareous species Cassidulina reniforme and Islandiella norcrossi, both found in glaciomarine environments under the influence of (chilled) Atlantic-sourced waters along the West Greenland coast 35 , 36 , 38 , 39 and the agglutinated species Adercotryma glomerata and Reophax catella. Cassidulina neoteretis is seen as an indicator of a true (warm) Atlantic water influence 37 , 40 , but as they were rare (≤ 6%) in our records are the grouped with the larger (chilled) Atlantic water group.…”