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Assessing changes in sea surface conditions due to the effects of past freshwater outflow through Baffin Bay and Davis Strait to the Labrador Sea, hereafter referred to as the Baffin Bay corridor, is relevant in understanding the variability in Labrador Sea Water (LSW) formation. Here, regional changes in oceanographic circulation and sea surface conditions are reconstructed based on organic-walled dinoflagellate cyst (dinocyst) assemblages from four cores collected from deep, central sites of the Baffin Bay corridor. All cores exhibit a major shift in dinocyst assemblages since the late glacial period. This shift consists of a change from a polar–subpolar heterotrophic species assemblage tolerating cold and near permanent ice-covered conditions, to assemblages characterized by a higher diversity and the occurrence of phototrophic taxa associated with mild conditions. Sea surface reconstructions from the modern analogue technique display a shift from harsh, quasi-perennial ice cover to warmer summer sea surface temperatures and a seasonal sea ice. South of the Davis Strait sill, this regime shift occurred at ca. 11.9 cal ka BP due to the influence of North Atlantic waters. Baffin Bay, however, remained densely sea ice covered until about 7.4 cal ka BP, when these warmer waters penetrated into Baffin Bay and mixed with the West Greenland Current (WGC). This mixing was facilitated by the retreat of the Greenland and Laurentide Ice Sheet (LIS) margins. A major change in Labrador Sea surface conditions occurred nearly at about the same time (~7.6 cal ka BP) when the strong stratification of surface waters weakened because of the reduction in meltwater supplies from the LIS that allowed winter convection and the inception of LSW formation. All these new records demonstrate large amplitude fluctuations in sea surface conditions tightly controlled by the relative strengths and shifts of the warmer WGC and colder Baffin Island Current. [ABSTRACT FROM AUTHOR]

To reconstruct oceanic primary productivity in the northern North Atlantic Ocean during the last glacial maximum (LGM), we have applied the modern analogue technique to dinocyst assemblages using a Northern Hemisphere database that includes 1171 reference sites. The reconstructions were made in LGM sediments (21 ±2 ka) of a set of 62 cores collected from 36°N to 75°N. Here, we present the compilation of reconstructed seasonal and annual productivity during the LGM. Results show lower mean annual productivity during the LGM than at present in the northern North Atlantic. At most high-latitude locations, LGM productivity has been estimated at <200 gC m–2 a–1, with extremely low values (<100 gC m–2 a–1) in the Labrador Sea, Baffin Bay, and along the margins of Greenland. Such low values might be the result of reduced Atlantic Meridional Overturning Circulation and stratified water that characterized the glacial episode of the North Atlantic Ocean. Dans le but de reconstituer quantitativement la productivité primaire de l’Atlantique Nord au cours du dernier maximum glaciaire, nous avons utilisé les assemblages des kystes de dinoflagellés préservés dans le sédiment. La reconstitution a été effectuées en se basant sur la méthode des meilleurs analogues modernes et en exploitant une base de données de référence de l’Hémisphère Nord incluant 1171 sites. Les reconstitutions ont été effectuées sur 62 carottes sédimentaires prélevées entre les latitudes 36 °N et 75 °N. Les résultats montrent que la productivité primaire annuelle était moindre pendant le dernier maximum glaciaire que d’actuellement. La productivité primaire du dernier maximum glaciaire dans les hautes latitudes de l’Atlantique Nord a été estimée à des valeurs inférieure à 200 gC m–2 a–1 avec des valeurs extrêmement faibles (<100 gC m–2 a–1) dans la mer du Labrador, la baie de Baffin et le long des côtes groenlandaises. De telles valeurs pourraient être le résultat d’une diminution de l’intensité de la circulation thermohaline dans l’Atlantique Nord et de l’intensification de la stratification des eaux qui ont caractérisé l’Atlantique Nord pendant cet épisode glaciaire. [ABSTRACT FROM AUTHOR]

Marine sedimentary cores were collected off western Greenland margins to reconstructchanges in sea-surface conditions during the Holocene and to document the climate-ocean-icedynamics. In the south, close to Nuuk in eastern Labrador Sea, core SA13-ST3-20G providedrecords with a centennial resolution over the last 12,000 years. North of Davis Strait, in theeastern Baffin Bay, core MSM343300 from Disko Bugt permitted to document changesthrough the last 10,000 years in complement to other Baffin Bay records (cf. Gibb et al. theHolocene 2015). The dinocyst assemblages provided information on past sea-surfaceconditions, including temperature (SST), salinity and sea ice based on modern analoguetechnique. Both cores recorded significant changes throughout the Holocene. At regionalscale, during the early Holocene, a change from harsh conditions with dense sea-icecover to interglacial conditions occurred in two steps: at ca. 10 ka BP significantdecrease of heterotrophic taxa (Islandinium minutum and Brigantedinium spp.) andthe occurrence of phototrophic taxa (Pentapharsodinium dalei, Spiniferites spp.Operculodinium centrocarpum), corresponds to an increase of summer SST and adecrease of the sea ice cover; after 7.5 ka BP, the establishment of full interglacialconditions both south and north of Davis Strait is marked by maximum percentages ofphototrophic taxa and the occurrence of Nematosphaeropsis labyrinthus in dinocystassemblages, which corresponds to onset of minimum sea ice, optimum SST and salinity.Optimal conditions persisted until about 2.5 ka BP south of Davis Strait and 1.5 ka BPin the Disko Bugt. The change towards more unstable conditions during the LateHolocene is notably marked by decrease in the percentages of Pentapharsodiniumdalei and increase of Islandinium cezare. It corresponds to spreading of sea iceand successive cooling pulses. The changes towards harsher and more unstableconditions seem to coincide with the disappearance of the Saqqaq culture at about3 ka BP and to the gap of human occupation in western Greenland, which wasrecorded from about 2 to 1 ka BP between the Dorset and the Norse settlements. [ABSTRACT FROM AUTHOR]

As polynyas are often used around the globe as a window on tomorrow's marine polar ecosystems, this study presents reconstructions of primary production and sea-surface conditions near the North Water polynya, since ~ 1560 CE from palynological, isotopic and biomarker analyses of a sediment core. Quantitative reconstructions of sea-surface conditions (temperature, sea-ice cover and production) were derived from the Modern Analogue Technique (MAT) applied to dinoflagellate cyst assemblages. Production was also qualitatively estimated from the stable isotope composition of organic carbon and nitrogen and the concentration of organic biomarkers (IP 25, dinosterols). The results show relatively stable oceanographic conditions but suggest a slight warming accompanied by an increase in productivity after 1860 CE. The comparison of MAT reconstructions and the organic biomarker data suggests that IP 25 provides information about primary production associated with sea-ice but does not unequivocally reflect sea-ice concentration in this regional setting, which is marked by dense seasonal sea ice except during the short summer season. [ABSTRACT FROM AUTHOR]