12 research outputs found
The marine and continental cryosphere in NW Greenland : holocene dynamics under a changing climate and interplay with the oceanographic context
ThĂšse en cotutelle : UniversitĂ© Laval, QuĂ©bec, Canada et UniversitĂ© de Bordeaux, Talence, FranceLe dĂ©troit de Nares constitue l'un des trois domaines de l'Archipel Arctique Canadien (AAC) reliant l'ocĂ©an Arctique Ă la baie de Baffin. Le potentiel d'eau douce transportĂ© via ces dĂ©troits atteint, au sud de la baie de Baffin, la mer du Labrador, et module ainsi les caractĂ©ristiques physico-chimiques des eaux de surface et de sub-surface de cette rĂ©gion, siĂšge de la formation d'une des composantes majeures de la circulation profonde de l'Atlantique Nord. Le dĂ©troit de Nares, Ă la frontiĂšre est de l'AAC, est Ă 80% couvert de glace de mer pendant 11 mois de l'annĂ©e sous l'influence (1) de l'apport de banquise multi-annuelle provenant de l'ocĂ©an Arctique au Nord, et (2) de la formation in situ de glace de mer. L'histoire hydrologique de cette rĂ©gion est donc intimement liĂ©e Ă celle de ces deux composantes. Par ailleurs, ce couvert de glace rĂ©gule le transport d'eaux dessalĂ©es et de glace vers la baie de Baffin, et entretient l'existence d'une zone ouverte : la polynie des eaux du nord. La polynie des eaux du nord est aujourd'hui essentiellement une polynie Ă chaleur latente. L'arc de glace du bassin de Kane empĂȘche la dĂ©rive de glace de mer et d'icebergs vers la baie de Baffin, pendant que les vents puissants chassent la glace formĂ©e Ă la surface de la polynie. Deux processus physiques important ont alors lieu : (1) la formation de glace de mer en continue entretient la formation de saumures ou « brines », des eaux salĂ©es et froides, et (2) sous l'effet du vent, les masses d'eaux de surface sont dĂ©viĂ©es vers l'Ăźle d'Ellesmere. Un mouvement vertical est initiĂ© par la plongĂ©e des brines et le pompage d'Ekman rĂ©sultant du dĂ©placement des masses d'eaux par le vent induit la remontĂ©e d'eaux atlantiques chaudes, riches en nutriments. La remontĂ©e d'eaux atlantiques peut promouvoir la fonte de la glace en surface, ce qui confĂšre Ă la polynie des eaux du nord son caractĂšre sensible. La productivitĂ© primaire est alimentĂ©e en continu par des eaux pacifiques riches en silicates Ă travers le dĂ©troit de Nares et la remontĂ©e d'eaux atlantiques riches en nitrates dans la polynie, jusqu'Ă la rupture estivale du pont de glace qui entraine l'entrĂ©e de glace dans la polynie et l'arrĂȘt de la remontĂ©e de nitrates. Depuis les annĂ©es 1980, la durĂ©e moyenne du pont de glace est en diminution, engendrant une chute de la productivitĂ©. Le dĂ©troit de Nares a Ă©tĂ© affectĂ© durant la pĂ©riode post-glaciaire par (1) un retrait rapide des calottes groenlandaise et innuitienne, initialement ancrĂ©es sur le fond et convergeant au niveau du dĂ©troit de Nares, (2) une baisse importante du niveau marin (rebond isostatique) et (3) des conditions variables de glace de mer pĂ©renne ou saisonniĂšre. Ces trois phĂ©nomĂšnes, dont la chronologie et le synchronisme Ă l'Ă©chelle rĂ©gionale sont trĂšs mal contraints, font du dĂ©troit de Nares un domaine unique d'examen de la rĂ©ponse de la cryosphĂšre marine et continentale Ă un changement climatique rapide tel celui amplifiĂ© aujourd'hui dans les rĂ©gions arctiques sous le forçage du rĂ©chauffement global. Les archives sĂ©dimentaires prĂ©levĂ©es lors des campagnes (2014 et 2016) du NGCC Amundsen dans le cadre de l'ANR GreenEdge et du programme canadien ArcticNet offrent une opportunitĂ© unique de reconstituer l'histoire post-glaciaire Ă tardi-holocĂšne de la rĂ©gion. Notre travail repose sur une analyse multi-proxies de ces archives incluant pour chaque carotte une Ă©tude sĂ©dimentologique approfondie (granulomĂ©trie et lithofaciĂšs), une analyse micropalĂ©ontologique (assemblages de foraminifĂšres benthiques et planctoniques), des mesures gĂ©ochimiques continues de la distribution d'Ă©lĂ©ments majeurs et mineurs (banc XRF core-scanner), des analyses minĂ©ralogiques (q-XRD) et des mesures biogĂ©ochimiques (biomarqueurs de la glace de mer IP25 et HBI III). Nos rĂ©sultats nous ont amenĂ© Ă proposer un Ăąge d'ouverture pour le dĂ©troit de Nares situĂ© entre 9 et 8.3 mille ans avant l'actuel (cal. ka BP), avec un Ăąge probable autour de 8.5-8.3 cal. ka BP. Les conditions environnementales suivant la connexion de l'ocĂ©an Arctique avec la baie de Baffin ont Ă©tĂ© trĂšs variables en lien avec le maximum thermique holocĂšne (induisant de trĂšs fortes tempĂ©ratures atmosphĂ©riques) et l'apport important d'eau de fonte liĂ© au recul des calottes. Dans un environnement plus glacio-distal, un minimum de couvert de glace de mer est observĂ© entre 8.1 et 7.5 cal. ka BP. Avec la chute de tempĂ©ratures atmosphĂ©riques, le couvert de glace de mer saisonniĂšre est Ă©tabli de façon rĂ©guliĂšre Ă partir de 7.5 cal. ka BP, mais ce n'est qu'Ă partir de 5.5 cal. ka BP que le pont de glace du bassin de Kane s'inscrit durablement au printemps et en Ă©tĂ©. La polynie est initiĂ©e Ă partir de 5.5 cal. ka BP, mais elle repose sur une chaleur essentiellement latente. Ce n'est qu'Ă partir de 4.5 cal. ka BP, lorsque les tempĂ©ratures atmosphĂ©riques sont assez froides, que la formation de brines est assez importante pour engendrer le transport vertical d'eaux atlantiques. A partir de 3.7/3.0 cal. ka BP, le pont de glace nord est prĂ©sent de façon quasi-pĂ©renne, ce qui empĂȘche l'entrĂ©e de glace de mer arctique Ă©paisse dans le dĂ©troit de Nares et abouti Ă la fragilisation du pont de glace dans le bassin de Kane. Le dĂ©troit de Nares devient libre de glace de façon saisonniĂšre et, du fait de l'absence de convection, les eaux de la rĂ©gion nord de la baie de Baffin deviennent stratifiĂ©es. Le rĂ©tablissement du pont de glace du bassin de Kane est limitĂ© Ă une courte pĂ©riode centrĂ©e autour de 500 ans avant l'actuel.Nares Strait is one of three channels of the Canadian Arctic Archipelago (CAA) which connect the Arctic Ocean to Baffin Bay. The CAA throughflow is a major component of ocean circulation in western Baffin Bay. Nares Strait borders the CAA to the east, separating Ellesmere Island from Greenland, and is 80% covered in sea ice 11 months of the year. The heavy sea ice cover is constituted of (1) Arctic (multi-year) sea-ice having entered the strait by the north, and (2) locally formed first year sea ice, which consolidates the ice cover. The hydrological history of the area is intimately linked to the formation of land-fast sea ice in the strait, constituting ice arches. The seaice cover in Nares Strait regulates freshwater (liquid and solid) export towards Baffin Bay, and is integral to the formation of an area of open water in northernmost Baffin Bay: The North Water polynya. Nares Strait has been at the heart of major geomorphological changes over the past 10,000 years. Its deglacial and post-glacial history is marked by (1) rapid retreat of the Greenland and Innuitian ice-sheets which coalesced along Nares Strait during the Last Glacial Maximum, (2) post-glacial shoaling associated to isostatic rebound, and (3) variable multi-year and seasonal sea ice conditions. Little is known about the evolution of these three environmental components of the Nares Strait history, and they are poorly constrained in terms of chronology and synchronism with other regional changes. Nares Strait and its eventful Holocene history provide a unique case study of the response of the marine and continental cryosphere to rapid climate change, such as that affecting Arctic regions in modern times. The marine sediment archives that were retrieved during the ANR GreenEdge and ArcticNet (2014 and 2016) cruises of CCGS Amundsen offer a unique opportunity to investigate the Deglacial to Late Holocene history of Nares Strait. Our reconstructions are based on a multi-proxy study of these cores, including sedimentologic (grain size and lithofacies), geochemical (XRF), mineralogical (q-XRD), micropaleontological (planktic and benthic foraminiferal assemblages), and biogeochemical (sea ice biomarkers IP25 and HBI III). Our results include an age for the Deglacial opening of Nares Strait between 9.0 and 8.3 cal. ka BP, with the event likely occurring closer to the later bracket of the timeframe (i.e., ca 8.5-8.3 cal. ka BP). This event established the throughflow from the Arctic Ocean towards northernmost Baffin Bay. Environmental conditions were highly unstable in the Early Holocene, and marine primary productivity was limited. A period of minimum sea-ice cover occurred from ca 8.1 to 7.5 cal. ka BP, during the Holocene Thermal Maximum, when atmospheric temperatures were higher than today in Nares Strait. Sea-ice cover became more stably established as a seasonal feature around 7.5 cal. ka BP and primary productivity related to ice edge blooms increased. Eventually, the duration of the ice arches increased and they were present in spring and into the summer from 5.5 to 3.7 cal. ka BP, which allowed the inception of the North Water polynya. The North Water reached its maximal potential between 4.5 and 3.7 cal. ka BP, when warmer Atlantic-sourced water upwelled in the polynya, providing nutrients for primary productivity. The establishment of a near-perennial ice arch in northern Nares Strait prevented export of multi-year sea ice into Nares Strait and hindered the formation of the southern ice arch, ultimately resulting in a less productive polynya over the past ca 3.0 cal. ka BP
Learning from the past : Impact of the Arctic Oscillation on sea ice and marine productivity off northwest Greenland over the last 9,000 years
Climate warming is rapidly reshaping the Arctic cryosphere and ocean conditions, with consequences for sea ice and pelagic productivity patterns affecting the entire marine food web. To predict how ongoing changes will impact Arctic marine ecosystems, concerted effort from various disciplines is required. Here, we contribute multi-decadal reconstructions of changes in diatom production and sea-ice conditions in relation to Holocene climate and ocean conditions off northwest Greenland. Our multiproxy study includes diatoms, sea-ice biomarkers (IP(25)and HBI III) and geochemical tracers (TOC [total organic carbon], TOC:TN [total nitrogen], delta C-13, delta N-15) from a sediment core record spanning the last c. 9,000 years. Our results suggest that the balance between the outflow of polar water from the Arctic, and input of Atlantic water from the Irminger Current into the West Greenland Current is a key factor in controlling sea-ice conditions, and both diatom phenology and production in northeastern Baffin Bay. Our proxy record notably shows that changes in sea-surface conditions initially forced by Neoglacial cooling were dynamically amplified by the shift in the dominant phase of the Arctic Oscillation (AO) mode that occurred at c. 3,000 yr BP, and caused drastic changes in community composition and a decline in diatom production at the study site. In the future, with projected dominant-positive AO conditions favored by Arctic warming, increased water column stratification may counteract the positive effect of a longer open-water growth season and negatively impact diatom production.Peer reviewe
Vulnerability of the North Water ecosystem to climate change
High Arctic ecosystems and Indigenous livelihoods are tightly linked and exposed to climate change, yet assessing their sensitivity requires a long-term perspective. Here, we assess the vulnerability of the North Water polynya, a unique seaice ecosystem that sustains the worldâs northernmost Inuit communities and several keystone Arctic species. We reconstruct mid-to-late Holocene changes in sea ice, marine primary production, and little auk colony dynamics through multi-proxy analysis of marine and lake sediment cores. Our results suggest a productive ecosystem by 4400â4200âcalâyrs b2k coincident with the arrival of the first humans in Greenland. Climate forcing during the late Holocene, leading to periods of polynya instability and marine productivity decline, is strikingly coeval with the human abandonment of Greenland from c. 2200â1200âcalâyrs b2k. Our long-term perspective highlights the future decline of the North Water ecosystem, due to climate warming and changing sea-ice conditions, as an important climate change risk
The marine and continental cryosphere in Nares Strait, Northwest Greenland: Holocene dynamics under a changing climate and interplay with the oceanographic context
Nares Strait is one of three channels of the Canadian Arctic Archipelago (CAA) which connect the Arctic Ocean to Baffin Bay. The CAA throughflow is a major component of ocean circulation in western Baffin Bay. Nares Strait borders the CAA to the east, separating Ellesmere Island from Greenland, and is 80% covered in sea ice 11 months of the year. The heavy sea ice cover is constituted of (1) Arctic (multi-year) sea-ice having entered the strait by the north, and (2) locally formed first year sea ice, which consolidates the ice cover. The hydrological history of the area is intimately linked to the formation of land-fast sea ice in the strait, constituting ice arches. The seaice cover in Nares Strait regulates freshwater (liquid and solid) export towards Baffin Bay, and is integral to the formation of an area of open water in northernmost Baffin Bay: The North Water polynya.Nares Strait has been at the heart of major geomorphological changes over the past 10,000 years. Its deglacial and post-glacial history is marked by (1) rapid retreat of the Greenland and Innuitian ice-sheets which coalesced along Nares Strait during the Last Glacial Maximum, (2) post-glacial shoaling associated to isostatic rebound, and (3) variable multi-year and seasonal sea ice conditions. Little is known about the evolution of these three environmental components of the Nares Strait history, and they are poorly constrained in terms of chronology and synchronism with other regional changes. Nares Strait and its eventful Holocene history provide a unique case study of the response of the marine and continental cryosphere to rapid climate change, such as that affecting Arctic regions in modern times.The marine sediment archives that were retrieved during the ANR GreenEdge and ArcticNet (2014 and 2016) cruises of CCGS Amundsen offer a unique opportunity to investigate the Deglacial to Late Holocene history of Nares Strait. Our reconstructions are based on a multi-proxy study of these cores, including sedimentologic (grain size and lithofacies), geochemical (XRF), mineralogical (q-XRD), micropaleontological (planktic and benthic foraminiferal assemblages), and biogeochemical (sea ice biomarkers IP25 and HBI III).Our results include an age for the Deglacial opening of Nares Strait between 9.0 and 8.3 cal. ka BP, with the event likely occurring closer to the later bracket of the timeframe (i.e., ca 8.5-8.3 cal. ka BP). This event established the throughflow from the Arctic Ocean towards northernmost Baffin Bay. Environmental conditions were highly unstable in the Early Holocene, and marine primary productivity was limited. A period of minimum sea-ice cover occurred from ca 8.1 to 7.5 cal. ka BP, during the Holocene Thermal Maximum, when atmospheric temperatures were higher than today in Nares Strait. Sea-ice cover became more stably established as a seasonal feature around 7.5 cal. ka BP and primary productivity related to ice edge blooms increased. Eventually, the duration of the ice arches increased and they were present in spring and into the summer from 5.5 to 3.7 cal. ka BP, which allowed the inception of the North Water polynya. The North Water reached its maximal potential between 4.5 and 3.7 cal. ka BP, when warmer Atlantic-sourced water upwelled in the polynya, providing nutrients for primary productivity. The establishment of a near-perennial ice arch in northern Nares Strait prevented export of multi-year sea ice into Nares Strait and hindered the formation of the southern ice arch, ultimately resulting in a less productive polynya over the past ca 3.0 cal. ka BP.Le dĂ©troit de Nares constitue lâun des trois domaines de lâArchipel Arctique Canadien (AAC) reliant lâocĂ©an Arctique Ă la baie de Baffin. Le potentiel d'eau douce transportĂ© via ces dĂ©troits atteint, au sud de la baie de Baffin, la mer du Labrador, et module ainsi les caractĂ©ristiques physico-chimiques des eaux de surface et de sub-surface de cette rĂ©gion, siĂšge de la formation dâune des composantes majeures de la circulation profonde de lâAtlantique Nord.Le dĂ©troit de Nares, Ă la frontiĂšre est de l'AAC, est Ă 80% couvert de glace de mer pendant 11 mois de lâannĂ©e sous lâinfluence (1) de lâapport de banquise multi-annuelle provenant de lâocĂ©an Arctique au Nord, et (2) de la formation in situ de glace de mer. Lâhistoire hydrologique de cette rĂ©gion est donc intimement liĂ©e Ă celle de ces deux composantes. Par ailleurs, ce couvert de glace rĂ©gule le transport d'eaux dessalĂ©es et de glace vers la baie de Baffin, et entretient l'existence d'une zone ouverte : la polynie des eaux du nord.La polynie des eaux du nord est aujourdâhui essentiellement une polynie Ă chaleur latente. Lâarc de glace du bassin de Kane empĂȘche la dĂ©rive de glace de mer et dâicebergs vers la baie de Baffin, pendant que les vents puissants chassent la glace formĂ©e Ă la surface de la polynie. Deux processus physiques important ont alors lieu : (1) la formation de glace de mer en continue entretient la formation de saumures ou « brines », des eaux salĂ©es et froides, et (2) sous lâeffet du vent, les masses dâeaux de surface sont dĂ©viĂ©es vers lâĂźle dâEllesmere. Un mouvement vertical est initiĂ© par la plongĂ©e des brines et le pompage dâEkman rĂ©sultant du dĂ©placement des masses dâeaux par le vent induit la remontĂ©e dâeaux atlantiques chaudes, riches en nutriments. La remontĂ©e dâeaux atlantiques peut promouvoir la fonte de la glace en surface, ce qui confĂšre Ă la polynie des eaux du nord son caractĂšre sensible. La productivitĂ© primaire est alimentĂ©e en continu par des eaux pacifiques riches en silicates Ă travers le dĂ©troit de Nares et la remontĂ©e dâeaux atlantiques riches en nitrates dans la polynie, jusquâĂ la rupture estivale du pont de glace qui entraĂźne lâentrĂ©e de glace dans la polynie et lâarrĂȘt de la remontĂ©e de nitrates. Depuis les annĂ©es 1980, la durĂ©e moyenne du pont de glace est en diminution, engendrant une chute de la productivitĂ©.Le dĂ©troit de Nares a Ă©tĂ© affectĂ© durant la pĂ©riode post-glaciaire par (1) un retrait rapide des calottes groenlandaise et innuitienne, initialement ancrĂ©es sur le fond et convergeant au niveau du dĂ©troit de Nares, (2) une baisse importante du niveau marin (rebond isostatique) et (3) des conditions variables de glace de mer pĂ©renne ou saisonniĂšre. Ces trois phĂ©nomĂšnes, dont la chronologie et le synchronisme Ă lâĂ©chelle rĂ©gionale sont trĂšs mal contraints, font du dĂ©troit de Nares un domaine unique dâexamen de la rĂ©ponse de la cryosphĂšre marine et continentale Ă un changement climatique rapide tel celui amplifiĂ© aujourdâhui dans les rĂ©gions arctiques sous le forçage du rĂ©chauffement global.Les archives sĂ©dimentaires prĂ©levĂ©es lors des campagnes (2014 et 2016) du NGCC Amundsen dans le cadre de lâANR GreenEdge et du programme canadien ArcticNet offrent une opportunitĂ© unique de reconstituer lâhistoire post-glaciaire Ă tardi-holocĂšne de la rĂ©gion. Notre travail repose sur une analyse multi-proxies de ces archives incluant pour chaque carotte une Ă©tude sĂ©dimentologique approfondie (granulomĂ©trie et lithofaciĂšs), une analyse micropalĂ©ontologique (assemblages de foraminifĂšres benthiques et planctoniques), des mesures gĂ©ochimiques continues de la distribution dâĂ©lĂ©ments majeurs et mineurs (banc XRF core-scanner), des analyses minĂ©ralogiques (q-XRD) et des mesures biogĂ©ochimiques (biomarqueurs de la glace de mer IP25 et HBI III).Nos rĂ©sultats nous ont amenĂ© Ă proposer un Ăąge dâouverture pour le dĂ©troit de Nares situĂ© entre 9 et 8.3 mille ans avant lâactuel (cal. ka BP), avec un Ăąge probable autour de 8.5-8.3 cal. ka BP. Les conditions environnementales suivant la connexion de lâocĂ©an Arctique avec la baie de Baffin ont Ă©tĂ© trĂšs variables en lien avec le maximum thermique holocĂšne (induisant de trĂšs fortes tempĂ©ratures atmosphĂ©riques) et lâapport important dâeau de fonte liĂ© au recul des calottes. Dans un environnement plus glacio-distal, un minimum de couvert de glace de mer est observĂ© entre 8.1 et 7.5 cal. ka BP. Avec la chute de tempĂ©ratures atmosphĂ©riques, le couvert de glace de mer saisonniĂšre est Ă©tabli de façon rĂ©guliĂšre Ă partir de 7.5 cal. ka BP, mais ce nâest quâĂ partir de 5.5 cal. ka BP que le pont de glace du bassin de Kane sâinscrit durablement au printemps et en Ă©tĂ©. La polynie est initiĂ©e Ă partir de 5.5 cal. ka BP, mais elle repose sur une chaleur essentiellement latente. Ce nâest quâĂ partir de 4.5 cal. ka BP, lorsque les tempĂ©ratures atmosphĂ©riques sont assez froides, que la formation de brines est assez importante pour engendrer le transport vertical dâeaux atlantiques. A partir de 3.7/3.0 cal. ka BP, le pont de glace nord est prĂ©sent de façon quasi-pĂ©renne, ce qui empĂȘche lâentrĂ©e de glace de mer arctique Ă©paisse dans le dĂ©troit de Nares et abouti Ă la fragilisation du pont de glace dans le bassin de Kane. Le dĂ©troit de Nares devient libre de glace de façon saisonniĂšre et, du fait de lâabsence de convection, les eaux de la rĂ©gion nord de la baie de Baffin deviennent stratifiĂ©es. Le rĂ©tablissement du pont de glace du bassin de Kane est limitĂ© Ă une courte pĂ©riode centrĂ©e autour de 500 ans avant lâactuel
Local and regional controls on Holocene sea ice dynamics and oceanography in Nares Strait, Northwest Greenland
International audienceNares Strait is one of three channels that connect the Arctic Ocean to Baffin Bay. Unique sea-ice conditions in the strait lead to the formation of landfast ice arches at its northern and southern ends. These ice arches regulate Arctic sea-ice and freshwater export through the strait and promote the opening of the North Water polynya. The present study addresses the paucity of pre-satellite records of environmental conditions in the Nares Strait area, and aims at reconstructing Holocene sea-ice conditions and ocean circulation in the strait. The investigation is based on a marine sediment core strategically retrieved from under the current ice arch in Kane Basin to the south of Nares Strait, and provides a continuous record spanning the past ca 9 kyrs. We use benthic foraminiferal assemblages and sea-ice biomarkers to infer changes in Holocene ocean circulation and sea-ice conditions in Kane Basin. The establishment of the modern ocean circulation in Kane Basin is related to ice sheet retreat and postglacial rebound, while changes in sea-ice cover concur with major shifts in the Arctic Oscillation (AO). Our results suggest that sea-ice cover in Kane Basin was highly variable between ca 9.0 and 8.3 cal. ka BP, before increasing, probably in link with the 8.2 cold event and the opening of Nares Strait. A short period of minimum sea-ice cover and maximum Atlantic bottom water influence occurred between ca 8.1 and 7.5 cal. ka BP, when Kane Basin was deeper than for the remaining of the Holocene. As atmospheric temperatures dropped, sea-ice cover intensified in Kane Basin between ca 7.5 and 5.5 cal. ka BP, but strong winds under prevailing positive-like AO conditions likely prevented the formation of ice arches in Nares Strait. During this time, our micro-paleontological data show that Atlantic water was progressively excluded from Kane Basin by the postglacial isostatic rebound. Increasingly cooler atmospheric temperatures and a shift towards more negative phases of the AO may have promoted the establishment of ice arches in Nares Strait between ca 5.5 and 3.0 cal. ka BP. Instabilities in the Kane Basin ice arch ca 3.0 cal. ka BP coincide with a shift towards prevailing positive phases of the AO, while a brief recovery of the ice arch occurred during more negative-like AO conditions between ca 1.2 and 0.2 cal. ka BP
Total sedimentary organic carbon and nitrogen analyses from marine sediment core AMD14-204_CASQ
Total sedimentary organic carbon contents (TOC; %), total nitrogen (TN; %), ratio TOC to TN, carbon and nitrogen isotopic compositions (â°) from the marine sediment core AMD14-204 that was retrieved from the West Greenland shelf, offshore Upernavik, and which spans the last ca. 9,000 years
Diatom concentrations and fluxes from marine sediment core AMD14-204_CASQ
Relative contribution of the âmarginal ice zoneâ, âdrift-ice/pack-iceâ and âsummer subsurfaceâ diatom indicator groups, diatom valve and Chaetoceros resting spore concentrations (valves or spores/g), diatom valve and Chaetoceros resting spore fluxes (valves or spores/unit surface area/yr), and total diatom fluxes (valves and spores/unit surface area/yr) from the marine sediment core AMD14-204 that was retrieved from the West Greenland shelf, offshore Upernavik, and which spans the last ca. 9,000 years
Fossil diatom record from marine sediment core AMD14-204_CASQ
Raw counts of fossil diatom taxa from the marine sediment core AMD14-204 that was retrieved from the West Greenland shelf, offshore Upernavik, and which spans the last ca. 9,000 years. Quantification was done using a light microscope (Olympus BX53, University of New Brunswick) with phase contrast optics, at 1000x magnification
Concentrations and fluxes of the sea-ice biomarkers 2,6,10,14-Tetramethyl-7-(3-methylpent-4-enyl)pentadecane (IP25) and highly branched isoprenoid triene (HBI III) from marine sediment core AMD14-204_CASQ
Concentrations of the sea-ice biomarker IP25 and highly branched isoprenoid triene (HBI III) (ng/g), total organic carbon content (TOC; %), IP25 and HBI III concentrations normalized to TOC (ng/gTOC), and fluxes of IP25 and HBI III (ng/unit surface area/yr) from the marine sediment core AMD14-204_CASQ that was retrieved from the West Greenland shelf, offshore Upernavik, and which spans the last ca. 9,000 years
Holocene polynya dynamics and their interaction with oceanic heat transport in northernmost Baffin Bay
Baffin Bay hosts the largest and most productive of the Arctic polynyas: the North Water (NOW). Despite its significance and active role in water mass formation, the history of the NOW beyond the observational era remains poorly known. We reconcile the previously unassessed relationship between long-term NOW dynamics and ocean conditions by applying a multiproxy approach to two marine sediment cores from the region that, together, span the Holocene. Declining influence of Atlantic Water in the NOW is coeval with regional records that indicate the inception of a strong and recurrent polynya from ~â4400 yrs BP, in line with Neoglacial cooling. During warmer Holocene intervals such as the Roman Warm Period, a weaker NOW is evident, and its reduced capacity to influence bottom ocean conditions facilitated northward penetration of Atlantic Water. Future warming in the Arctic may have negative consequences for this vital biological oasis, with the potential knock-on effect of warm water penetration further north and intensified melt of the marine-terminating glaciers that flank the coast of northwest Greenland