Reconstruction of Holocene oceanographic conditions in eastern Baffin Bay Katrine Elnegaard Hansen, Jacques Giraudeau, Lukas Wacker, Christof Pearce, Seidenkrantz Marit-Solveig To cite this version: Katrine Elnegaard Hansen, Jacques Giraudeau, Lukas Wacker, Christof Pearce, Seidenkrantz Marit- Solveig. Reconstruction of Holocene oceanographic conditions in eastern Baffin Bay. Climate of the Past, European Geosciences Union (EGU), 2020, 16, pp.1075 - 1095. 10.5194/cp-16-1075-2020. hal-02991681 HAL Id: hal-02991681 https://hal.archives-ouvertes.fr/hal-02991681 Submitted on 6 Nov 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. 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Reconstruction of Holocene oceanographic conditions in eastern Baffin Bay Katrine Elnegaard Hansen1, Jacques Giraudeau2, Lukas Wacker3, Christof Pearce1, and Marit-Solveig Seidenkrantz1 1Department of Geoscience, Arctic Research Centre and iClimate, Aarhus University, Aarhus, Denmark 2Centre national de la recherche scientifique (CNRS), Université de Bordeaux, UMR 5805, Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), Bordeaux, France 3Laboratory of Ion Beam Physics, ETH, Zürich, Switzerland Correspondence: Katrine Elnegaard Hansen ([email protected]) Received: 18 December 2019 – Discussion started: 10 January 2020 Revised: 21 April 2020 – Accepted: 1 May 2020 – Published: 22 June 2020 Abstract. Baffin Bay is a semi-enclosed basin connecting Late Holocene, only interrupted by short-lived warmings su- the Arctic Ocean and the western North Atlantic, thus mak- perimposed on this cooling trend. ing out a significant pathway for heat exchange. Here we re- construct the alternating advection of relatively warmer and saline Atlantic waters versus the incursion of colder Arctic water masses entering Baffin Bay through the multiple gate- 1 Introduction ways in the Canadian Arctic Archipelago and the Nares Strait during the Holocene. We carried out benthic foraminiferal The opening of the Nares Strait and the narrower gateways assemblage analyses, X-ray fluorescence scanning, and ra- of the Canadian Arctic Archipelago was initiated towards diocarbon dating of a 738 cm long marine sediment core the end of the last glacial. It was completed in the Early retrieved from eastern Baffin Bay near Upernavik, Green- Holocene at 9.3–8.3 ka when parts of the Greenland and In- land (Core AMD14-204C; 987 m water depth). Results re- nuitian ice sheets, blocking these gateways, had fully re- veal that eastern Baffin Bay was subjected to several oceano- treated from the area (Jennings et al., 2019, 2011; Georgiadis graphic changes during the last 9.2 kyr. Waning deglacial et al., 2018; England et al., 2006; Zreda et al., 1999). The conditions with enhanced meltwater influxes and an exten- opening of these gateways presumably had a significant im- sive sea-ice cover prevailed in eastern Baffin Bay from 9.2 pact on the general oceanic circulation in Baffin Bay and the to 7.9 ka. A transition towards bottom water amelioration is Labrador Sea, allowing the input of cold Arctic water masses recorded at 7.9 ka by increased advection of Atlantic water to these regions (Jennings et al., 2019, 2017). masses, encompassing the Holocene Thermal Maximum. A The modern marine environment of Baffin Bay is charac- cold period with growing sea-ice cover at 6.7 ka interrupts terized by a combination of warm Atlantic and cold polar the overall warm subsurface water conditions, promoted by waters. The West Greenland Current (WGC), which flows a weaker northward flow of Atlantic waters. The onset of the northward along the coast of west Greenland, carries mixed, neoglaciation at ca. 2.9 ka is marked by an abrupt transition warm, Atlantic-sourced Irminger Current (IC) water and towards a benthic fauna dominated by agglutinated species, cold and fresh waters of the East Greenland Current (EGC) likely in part explained by a reduction of the influx of At- (Drinkwater, 1996). The onset of the present configuration lantic Water, allowing an increased influx of the cold, cor- of the WGC during the late glacial (Jennings et al., 2017, rosive Baffin Bay Deep Water originating from the Arctic 2018) enabled the advection of Atlantic-sourced waters from Ocean to enter Baffin Bay through the Nares Strait. These the south along the west coast of Greenland into Baffin Bay. cold subsurface water conditions persisted throughout the These waters progressively expanded from the shelf edge to shallow shelf areas during the deglaciation following the re- treat of the Greenland Ice Sheet (Jennings et al., 2017; Shel- Published by Copernicus Publications on behalf of the European Geosciences Union. 1076 K. E. Hansen et al.: Reconstruction of Holocene oceanographic conditions in eastern Baffin Bay don et al., 2016). Today, Atlantic Water reaches the locations tion of warmer Atlantic waters into the fjord (Andresen et al., of Thule (76◦ N) and the southern part of the Nares Strait at 2014; Vermassen et al., 2019). its northernmost extension off west Greenland (Buch, 1994; An area of maximum 80 000 km2 in north-western Baffin Funder, 1990; Knudsen et al., 2008). Bay is occupied by the North Water Polynya (Dunbar and Several studies suggest that eastern Baffin Bay has been Dunbar, 1972; Tremblay et al., 2002). The prevailing north- subjected to a series of oceanographic and palaeoclimatic westerly winds carry newly formed sea ice away from the changes during the Holocene, induced by changes in the polynya (Bi et al., 2019), limiting the formation of a thick strength of the WGC linked to fluctuations in Atlantic Wa- sea-ice cover and resulting in open-water conditions, exten- ter entrainment and thus to changes in the Atlantic Merid- sive heat loss to the atmosphere, and high marine productiv- ional Overturning Circulation (AMOC). Most of these stud- ity (Melling et al., 2010). The sea ice that is exported from ies focused on the southern and central shelf regions of west the polynya contributes to brine formation, which may lead Greenland (Erbs-Hansen et al., 2013; Moros et al., 2016; to the sinking of dense and cold surface waters. The sustain- Lloyd et al., 2007; Perner et al., 2012; Seidenkrantz et al., ment of the polynya is highly dependent on strong north- 2007), but few investigated the past dynamics of the WGC in westerly winds and the continuous formation of an ice bridge the eastern sector of Baffin Bay. at Smith Sound (Fig. 1a) preventing sea ice from entering In this study, we investigate potential changes in the influx Baffin Bay through the Nares Strait (Dunbar and Dunbar, of Atlantic-sourced water to eastern Baffin Bay through the 1972; Melling et al., 2010). Holocene, discussing the hypothesis that changes in Baffin The modern ocean surface circulation in Baffin Bay is Bay environmental conditions are closely linked to overall driven by the local atmospheric circulation system affect- changes in the Atlantic Meridional Overturning Circulation. ing the strength of the north-westerly winds, creating an Our study is based on micropalaeontological and geochem- overall cyclonic ocean circulation pattern (Drinkwater, 1996) ical investigations of a marine sediment core retrieved near (Fig. 1a). From the south near Cape Farewell, the mixed Upernavik in eastern Baffin Bay. This site is located in the WGC carries relatively warm saline water from the Irminger flow path of the WGC and in the vicinity of the marine out- Current (IC) and cold ice-loaded polar waters from the East let glacier Upernavik Isstrøm (Fig. 1b). Faunal assemblage Greenland Current (EGC) towards the north over the shelf re- analysis of benthic foraminifera, radiocarbon datings, and X- gion of the west Greenland margin (Drinkwater, 1996; Mün- ray fluorescence (XRF) data enable the reconstruction of the chow et al., 2015), creating the West Greenland Intermedi- palaeoceanography and palaeoclimate of eastern Baffin Bay, ate Water (Tang et al., 2004). The IC water component is including the temporal and spatial development of the water mainly constrained to the continental slope in the depth range exchange in Baffin Bay during the Holocene. of 200–1000 m, whereas the EGC component is more shelf oriented and thus shallower (200 m), (Buch, 1994; Rykova Regional setting et al., 2015). The WGC bifurcates into two branches upon reaching the Davis Strait (Cuny et al., 2002). Here, one Baffin Bay is a semi-enclosed basin constrained by Baffin branch flows towards the west and eventually meets and joins Island to the west, Ellesmere Island to the north-west, and the Outer Labrador Current and heads south (Cuny et al., Greenland to the east (Fig.