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Micropaleontological analyses of a sediment core raised in Disko Bugt (West of Greenland) were undertaken in order to document paleoceanographical changes in the eastern Baffin Bay during the Holocene. The modern analogue technique (MAT) applied to dinocyst assemblages provided information on paleo-sea-surface conditions, whereas isotopic analyses of benthic foraminifers aimed at documenting the 'deep' water mass occupying the site. During the earlier interval recorded (~10 to ~7.3 cal. kyr BP), important discharge of ice and meltwater from the Greenland Ice Sheet (GIS) margin, notably through the Jakobshavn Isbrae, resulted in harsh conditions with a dense sea-ice cover and low temperatures, productivity, and foraminiferal abundances. Postglacial conditions settled at ~7.3 cal. kyr BP, with a sharp rise in dinocyst abundance and species diversity, which led to reconstruct increase in summer temperatures. We link this transition to the advection of West Greenland Current waters in the upper part of the water column after the reduction of meltwater inputs from GIS. Optimal temperature conditions reaching up to >10°C were finally achieved in surface waters at ~6 cal. kyr BP. Slight cooling pulses were then recorded at ~4.2-4 and ~1.5-1 cal. kyr BP, and the final optimum recorded in surface temperature from ~1 to 0.8 cal. kyr BP is associated with the 'Medieval Warm Period'. Throughout the postglacial interval, the data suggest an opposition between sea-surface temperatures and salinity, with warmer intervals being characterized by lower salinity waters, probably as a result of the higher freshwater discharge along the ice margin and notably the Jakobshavn Isbrae.
Palynological analyses of sediment core MSM343310 from Disko Bugt (68°38′861°N, 53°49′493°W) document decadal‐ to centennial‐scale variability of sea surface conditions during the last ~3,600 years. Dinocyst fluxes (>104 cysts/cm2 yr−1) indicate a very high productivity. Dinocyst assemblages dominated by Islandinium minutum, Brigantedinium spp., Islandinium? cezare, and the cyst of Pentapharsodinium dalei suggest low surface salinity and marked shifts in summer sea surface temperature. The application of the modern analog technique to dinocyst assemblages, using an updated reference data set with new sites from the West Greenland margin, led to reconstruct decadal‐centennial‐scale variations in sea surface salinity and temperature, in phase with the δ18O variations in the Camp Century ice core. At ~1.5 ka BP, the seasonal sea ice cover records an important regime change, from winter‐only sea ice to more unstable conditions marked by successive cooling pulses with sea ice cover of up to 8 months/yr. The data suggest a close relationship between hydrographic conditions and regional climate over Greenland. Our record shows variations with a mean 200 years periodicity until ~2 ka BP, which supports the hypothesis of climate variations driven by solar variability. After 1.5 ka BP, our data show a variability characterized by a 60–70 year periodicity, which suggests linkages with the Atlantic Multidecadal Oscillation and southwestward migration of the atmospheric polar front. The most recent part of the record, from ~1900 CE to 2007 CE, is characterized by assemblages reflecting warmer surface conditions and reduced sea ice cover.
Centennial-to-millennial temperature records of the past provide a context for the interpretation of current and future changes in climate. Quaternary climates have been relatively well studied in north-east North America and the adjacent Atlantic Ocean over the last decades, and new research methods have been developed to improve reconstructions. We present newly inferred reconstructions of sea surface temperature for the north-western Atlantic region, together with a compilation of published temperature records. The database thus comprises a total of 86 records from both marine and terrestrial sites, including lakes, peatlands, ice and tree rings, each covering at least part of the Holocene. For each record, we present details on seasons covered, chronologies and information on radiocarbon dates and analytical time steps. The 86 records contain a total of 154 reconstructions of temperature and temperature-related variables. Main proxies include pollen and dinocysts, while summer was the season for which the highest number of reconstructions were available. Many records covered most of the Holocene, but many dinocyst records did not extend to the surface, due to sediment mixing, and dendroclimate records were limited to the last millennium. The database allows for the exploration of linkages between sea ice and climate and may be used in conjunction with other palaeoclimate and palaeoenvironmental records, such as wildfire records and peatland dynamics. This inventory may also aid the identification of gaps in the geographic distribution of past temperature records thus guiding future research efforts. K E Y W O R D SCanada, climate, dinocyst, palaeo, proxy | 39 van BELLEn Et aL.
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