scholarly journals Late and Postglacial Paleoenvironments of the Gulf of St. Lawrence: Marine and Terrestrial Palynological Evidence

2007 ◽  
Vol 47 (2) ◽  
pp. 167-180 ◽  
Author(s):  
Anne de Vernal ◽  
Joël Guiot ◽  
Jean-Louis Turon
Keyword(s):  
Surface Water ◽  
Sea Ice ◽  
Sea Surface ◽  
Early Holocene ◽  
Laurentide Ice Sheet ◽  
Gulf Region ◽  
Low Salinity ◽  
Cooling Phase ◽  
Summer Temperatures ◽  
Younger Dryas Event

ABSTRACT Cored sediments from Anticosti and Esquiman channels and from Cabot Strait have been analyzed for their palynological content, which includes pollen and spores and dinoflagellate cysts. The dinoflagellate cyst assemblages led to the establishment of a regional ecostratigraphy and to quantitative reconstruction of changes in sea-surface conditions using transfer function (best analogue method). Prior to about 10,000 BP, assemblages dominated by Brigantedinium are associated with relatively cold (4-100C in August) surface water and extensive seasonal sea-ice cover (up to 8 months/yr.); in Cabot Strait low salinity conditions (25-27%o) were recorded from about 11,800 to 10,000 BP as the result of outflow of meltwater discharge from the Laurentide Ice Sheet. Between ca. 11,000 and 10,500 BP a cooling phase in surface water probably corresponds to the Younger Dryas event. At about 10,000 BP, a sharp transition marked by the occurrence of abundant Gonyaulacales, corresponds to the establishment of conditions similar to the present with summer temperatures up to 160C, salinity of -31 %o and a seasonal extent of sea-ice of about 2 months/yr. During the Holocene, slight fluctuations of sea-surface temperature are reconstructed, and a thermal optimum is recorded at about 6000 BP. The pollen and spore assemblages led to direct correlations with the onshore palynostratigraphy. In the northern Gulf region, Picea migration apparently rapidly followed the early Holocene surface water warming although the development of closed coniferous forests occurred much later. In the southern part of the Gulf, the Picea forest expansion coincides with the early Holocene increase of temperature, and the significant occurrence of Tsuga followed the middle Holocene thermal optimum as recorded in sea-surface water.

scholarly journals Atlantic Water advection vs glacier dynamics in northern Spitsbergen since early deglaciation

2017 ◽  
Author(s):  
Martin Bartels ◽  
Jürgen Titschack ◽  
Kirsten Fahl ◽  
Rüdiger Stein ◽  
Marit-Solveig Seidenkrantz ◽  
...  
Keyword(s):  
Sea Ice ◽  
Environmental Conditions ◽  
Late Holocene ◽  
Ice Cover ◽  
Atlantic Water ◽  
Sea Surface ◽  
Early Holocene ◽  
Sea Surface Temperatures ◽  
Surface Temperatures ◽  
Glacier Dynamics

Abstract. Atlantic Water (AW) advection plays an important role for climatic, oceanographic and environmental conditions in the eastern Arctic. Situated along the only deep connection between the Atlantic and the Arctic Ocean, the Svalbard Archipelago is an ideal location to reconstruct the past AW advection history and document its linkage with local glacier dynamics, as illustrated in the present study of a sedimentary record from Woodfjorden (northern Spitsbergen) spanning the last ~ 15 500 years. Sedimentological, micropalaeontological and geochemical analyses were used to reconstruct changes in marine environmental conditions, sea-ice cover and glacier activity. Data illustrate a partial breakup of the Svalbard–Barents–Sea Ice Sheet from Heinrich Stadial 1 onwards (until ~ 14.6 ka BP). During the Bølling-Allerød (~ 14.6–12.7 ka BP), AW penetrated as a bottom water mass into the fjord system and contributed significantly to the destabilisation of local glaciers. During the Younger Dryas (~ 12.7–11.7 ka BP), it intruded into intermediate waters while evidence for a glacier advance is lacking. A short-term deepening of the halocline occurred at the very end of this interval. During the early Holocene (~ 11.7–7.8 ka BP), mild conditions led to glacier retreat, a reduced sea-ice cover and increasing sea surface temperatures, with a brief interruption during the Preboreal Oscillation (~ 11.1–10.8 ka BP). During the late Holocene (~ 1.8–0.4 ka BP), a slightly reduced AW inflow and lower sea surface temperatures compared to the early Holocene are reconstructed. Glaciers, which previously retreated to the shallower inner parts of the Woodfjorden system, likely advanced during the late Holocene. In particular, as topographic control in concert with the reduced summer insolation partly decoupled glacier dynamics from AW advection during this recent interval.

scholarly journals A rapid transition from ice covered CO<sub>2</sub>–rich waters to a biologically mediated CO<sub>2</sub> sink in the eastern Weddell Gyre

2008 ◽  
Vol 5 (5) ◽  
pp. 1373-1386 ◽  
Author(s):  
D. C. E. Bakker ◽  
M. Hoppema ◽  
M. Schröder ◽  
W. Geibert ◽  
H. J. W. de Baar
Keyword(s):  
Surface Water ◽  
Sea Ice ◽  
Deep Water ◽  
Dissolved Inorganic Carbon ◽  
Ice Cover ◽  
Weddell Sea ◽  
Sea Surface ◽  
Upward Movement ◽  
Weddell Gyre ◽  
Warm Deep Water

Abstract. Circumpolar Deep Water (CDW), locally called Warm Deep Water (WDW), enters the Weddell Gyre in the southeast, roughly at 25° E to 30° E. In December 2002 and January 2003 we studied the effect of entrainment of WDW on the fugacity of carbon dioxide (fCO2) and dissolved inorganic carbon (DIC) in Weddell Sea surface waters. Ultimately the fCO2 difference across the sea surface drives air-sea fluxes of CO2. Deep CTD sections and surface transects of fCO2 were made along the Prime Meridian, a northwest-southeast section, and along 17° E to 23° E during cruise ANT XX/2 on FS Polarstern. Upward movement and entrainment of WDW into the winter mixed layer had significantly increased DIC and fCO2 below the sea ice along 0° W and 17° E to 23° E, notably in the southern Weddell Gyre. Nonetheless, the ice cover largely prevented outgassing of CO2 to the atmosphere. During and upon melting of the ice, biological activity rapidly reduced surface water fCO2 by up to 100 μatm, thus creating a sink for atmospheric CO2. Despite the tendency of the surfacing WDW to cause CO2 supersaturation, the Weddell Gyre may well be a CO2 sink on an annual basis due to this effective mechanism involving ice cover and ensuing biological fCO2 reduction. Dissolution of calcium carbonate (CaCO3) in melting sea ice may play a minor role in this rapid reduction of surface water fCO2.

scholarly journals A rapid transition from ice covered CO<sub>2</sub>-rich waters to a biologically mediated CO<sub>2</sub> sink in the eastern Weddell Gyre

2008 ◽  
Vol 5 (2) ◽  
pp. 1205-1235 ◽  
Author(s):  
D. C. E. Bakker ◽  
M. Hoppema ◽  
M. Schröder ◽  
W. Geibert ◽  
H. J. W. de Baar
Keyword(s):  
Surface Water ◽  
Sea Ice ◽  
Deep Water ◽  
Ice Cover ◽  
Weddell Sea ◽  
Sea Surface ◽  
Atmospheric Co2 ◽  
Upward Movement ◽  
Weddell Gyre ◽  
Co2 Sink

Abstract. Circumpolar Deep Water (CDW), locally called Warm Deep Water (WDW), enters the Weddell Gyre in the southeast, roughly at 25° E to 30° E. In December~2002 and January 2003} we studied the effect of entrainment of WDW on the fugacity of carbon dioxide (fCO2) and dissolved inorganic carbon (DIC) in Weddell Sea surface waters. Ultimately the fCO2 difference across the sea surface drives CO2 air-sea fluxes. Deep CTD sections and surface transects of fCO2 were made along the Prime Meridian, a northwest-southeast section, and along 17° E to 23° E during cruise ANT XX/2 on FS Polarstern. Upward movement and entrainment of WDW into the winter mixed layer had significantly increased DIC and fCO2 below the sea ice along 0° W and 17° E to 23° E, notably in the southern Weddell Gyre. Nonetheless, the ice cover largely prevented outgassing of CO2 to the atmosphere. During and upon melting of the ice, biological activity rapidly reduced surface water fCO2 by up to 100 μatm, thus creating a sink for atmospheric CO2. Despite the tendency of the surfacing WDW to cause CO2 supersaturation, the Weddell Gyre may well be a CO2 sink on an annual basis due to this effective mechanism involving ice cover and ensuing biological fCO2 reduction. Dissolution of calcium carbonate (CaCO3) in melting sea ice may also play a role in this rapid reduction of surface water fCO2. The CO2 source tendency deriving from the upward movement of "pre-industrial" CDW is declining, as atmospheric CO2 levels continue to increase, and thus the CO2 sink of the Weddell Gyre will continue to increase as well (provided the upward movement of WDW does not change significantly).

scholarly journals Planktic foraminifera and structure of surface water masses at the SW Svalbard margin in relation to climate changes during the last 2000 years

2018 ◽  
Author(s):  
Katarzyna Zamelczyk ◽  
Tine Lander Rasmussen ◽  
Markus Raitzsch ◽  
Melissa Chierici
Keyword(s):  
Surface Water ◽  
Sea Ice ◽  
Time Scale ◽  
Climate Changes ◽  
Water Masses ◽  
Warm Period ◽  
Sea Surface ◽  
Planktic Foraminifera ◽  
Near Surface ◽  
Surface Conditions

Abstract. We present a high-resolution record of properties in the subsurface (250–100 m), near surface (100–30 m) and surface (30–0 m) water masses at the SW Svalbard margin in relation to climate changes during the last 2000 years. The study is based on planktic foraminiferal proxies including the distribution patterns of planktic foraminiferal faunas, δ18O and δ13C values measured on Neogloboquadrina pachyderma, Turborotalita quinqueloba, and Globigerinita uvula, Mg / Ca-, δ18O- and transfer function-based sea surface temperatures, mean shell weights and other geochemical and sedimentological data. We compared paleo-data with modern planktic foraminiferal fauna distributions and the carbonate chemistry of the surface ocean. The results showed that cold sea surface conditions prevailed at ~ 400–800 AD and ~ 1400–1950 AD are associated with the local expression of the Dark Ages Cold Period and Little Ice Age, respectively. Warm sea surface conditions occurred at ~ 21–400 AD, ~ 800–1400 AD and from ~ 1950 AD until present and are linked to the second half of the Roman Warm Period, Medieval Warm Period and recent warming, respectively. On the centennial to multi-centennial time scale, sea surface conditions seem to be governed by the inflow of Atlantic water masses (subsurface and surface) and the presence of sea-ice and the variability of sea-ice margin (near surface water masses). However, the close correlation of sea surface temperature recorded by planktic foraminifera with total solar irradiance implies that solar activity could have exerted a dominant influence on the sea surface conditions on the decadal to multidecadal time scale.

scholarly journals Properties of surface water masses in the Laptev and the East Siberian seas in summer 2018 from in situ and satellite data

Ocean Science ◽  
2021 ◽  
Vol 17 (1) ◽  
pp. 221-247
Author(s):  
Anastasiia Tarasenko ◽  
Alexandre Supply ◽  
Nikita Kusse-Tiuz ◽  
Vladimir Ivanov ◽  
Mikhail Makhotin ◽  
...  
Keyword(s):  
Surface Water ◽  
Sea Ice ◽  
Satellite Data ◽  
Sea Water ◽  
Water Masses ◽  
Sea Surface ◽  
Ekman Transport ◽  
Synoptic Scale ◽  
Marginal Ice Zone

Abstract. Variability of surface water masses of the Laptev and the East Siberian seas in August–September 2018 is studied using in situ and satellite data. In situ data were collected during the ARKTIKA-2018 expedition and then complemented with satellite-derived sea surface temperature (SST), salinity (SSS), sea surface height, wind speed, and sea ice concentration. The estimation of SSS fields is challenging in high-latitude regions, and the precision of soil moisture and ocean salinity (SMOS) SSS retrieval is improved by applying a threshold on SSS weekly error. For the first time in this region, the validity of DMI (Danish Meteorological Institute) SST and SMOS SSS products is thoroughly studied using ARKTIKA-2018 expedition continuous thermosalinograph measurements and conductivity–temperature–depth (CTD) casts. They are found to be adequate to describe large surface gradients in this region. Surface gradients and mixing of the river and the sea water in the ice-free and ice-covered areas are described with a special attention to the marginal ice zone at a synoptic scale. We suggest that the freshwater is pushed northward, close to the marginal ice zone (MIZ) and under the sea ice, which is confirmed by the oxygen isotope analysis. The SST-SSS diagram based on satellite estimates shows the possibility of investigating the surface water mass transformation at a synoptic scale and reveals the presence of river water on the shelf of the East Siberian Sea. The Ekman transport is calculated to better understand the pathway of surface water displacement on the shelf and beyond.

scholarly journals Atlantic Water advection vs. glacier dynamics in northern Spitsbergen since early deglaciation

2017 ◽  
Vol 13 (12) ◽  
pp. 1717-1749 ◽  
Author(s):  
Martin Bartels ◽  
Jürgen Titschack ◽  
Kirsten Fahl ◽  
Rüdiger Stein ◽  
Marit-Solveig Seidenkrantz ◽  
...  
Keyword(s):  
Sea Ice ◽  
Environmental Conditions ◽  
Late Holocene ◽  
Ice Cover ◽  
Atlantic Water ◽  
Sea Surface ◽  
Early Holocene ◽  
Sea Surface Temperatures ◽  
Surface Temperatures ◽  
Glacier Dynamics

Abstract. Atlantic Water (AW) advection plays an important role in climatic, oceanographic and environmental conditions in the eastern Arctic. Situated along the only deep connection between the Atlantic and the Arctic oceans, the Svalbard Archipelago is an ideal location to reconstruct the past AW advection history and document its linkage with local glacier dynamics, as illustrated in the present study of a 275 cm long sedimentary record from Woodfjorden (northern Spitsbergen; water depth: 171 m) spanning the last  ∼  15 500 years. Sedimentological, micropalaeontological and geochemical analyses were used to reconstruct changes in marine environmental conditions, sea ice cover and glacier activity. Data illustrate a partial break-up of the Svalbard–Barents Sea Ice Sheet from Heinrich Stadial 1 onwards (until  ∼  14.6 ka). During the Bølling–Allerød ( ∼  14.6–12.7 ka), AW penetrated as a bottom water mass into the fjord system and contributed significantly to the destabilization of local glaciers. During the Younger Dryas ( ∼  12.7–11.7 ka), it intruded into intermediate waters while evidence for a glacier advance is lacking. A short-term deepening of the halocline occurred at the very end of this interval. During the early Holocene ( ∼  11.7–7.8 ka), mild conditions led to glacier retreat, a reduced sea ice cover and increasing sea surface temperatures, with a brief interruption during the Preboreal Oscillation ( ∼  11.1–10.8 ka). Due to a  ∼  6000-year gap, the mid-Holocene is not recorded in this sediment core. During the late Holocene ( ∼  1.8–0.4 ka), a slightly reduced AW inflow and lower sea surface temperatures compared to the early Holocene are reconstructed. Glaciers, which previously retreated to the shallower inner parts of the Woodfjorden system, likely advanced during the late Holocene. In particular, topographic control in concert with the reduced summer insolation partly decoupled glacier dynamics from AW advection during this recent interval.

Deglaciation of the Northeast Greenland ice stream and interaction with ocean circulation

2020 ◽  
Author(s):  
Jerry Lloyd ◽  
Louise Callard ◽  
Colm O'Cofaigh ◽  
David Roberts ◽  
Kaarina Weckstrom ◽  
...  
Keyword(s):  
Surface Water ◽  
Sea Ice ◽  
Ocean Circulation ◽  
Greenland Ice Sheet ◽  
Atlantic Water ◽  
Early Holocene ◽  
Sea Ice Concentration ◽  
Tidewater Glaciers ◽  
Ice Stream ◽  
Ice Concentration

&lt;p&gt;Large sections of the Greenland Ice Sheet (GrIS) drain directly to the ocean through tidewater glaciers and are, therefore, sensitive to changes in ocean circulation through time. Recent research has identified the dynamic response of many tidewater glaciers draining the GrIS showing thinning, flow acceleration and, in many cases, the break-up and retreat of fringing ice shelves and calving margins. This instability has been linked to incursion of relatively warm Atlantic Water as well as increased air temperatures and sea-ice loss.&lt;/p&gt;&lt;p&gt;The Northeast Greenland Ice Stream (NEGIS) is one of the largest ice streams draining approximately 15% of the GrIS with a sea level equivalent of ~ 1.4 m. Recent observations have identified ice shelf loss and grounding line retreat of Zachariae Isstrom, the southern arm of the NEGIS, post 2010 suggesting this sector of the GrIS might be starting to respond to climate forcing. The primary aim of the &amp;#8216;NEGIS&amp;#8217; project is to reconstruct the history of NEGIS since the Last Glacial Maximum (LGM) to improve our understanding of the interaction between NEGIS and climate (specifically ocean circulation). A series of sediment cores were collected along with bathymetric and sub-bottom profiler data concentrating on the Westwind and Norske Trough systems, two cross-shelf troughs originating from the present day margin of NEGIS. The data were collected through collaboration with the Alfred Wegener Institute as part of the GRIFF project supported by two cruises of the RV Polarstern in 2016 and 2017.&lt;/p&gt;&lt;p&gt;This presentation will focus on the deglaciation and palaeoceanographic evolution of the inner section of Norske Trough (inner continental shelf) investigating the interaction between ocean circulation and the dynamics of the tidewater margins of NEGIS. We present multiproxy results from a spliced box core and 10 m long gravity core collected from the same location covering the last 11,000 cal years. We use the benthic foraminiferal fauna and stable isotope signature to investigate variability in ocean circulation, specifically the relative strength of the Atlantic Water inflow along Norske Trough to the present day ice margin. We also investigate surface water conditions (including sea ice concentration) based on diatoms, dinoflagellates, IP&lt;sub&gt;25&lt;/sub&gt; and planktic foraminiferal stable isotopes. Our benthic foraminiferal assemblages record the variability in strength of Atlantic Water flow since deglaciation indicating relatively strong Atlantic Water flux during deglaciation reaching a peak during the early Holocene. Surface water proxies indicate variability in meltwater flux and sea ice concentration from the early Holocene. These results provide the first evidence for a variable ocean circulation with the potential to influence ice margin dynamics during deglaciation and through the Holocene.&lt;/p&gt;

Physical Control of Phytoplankton Production under Sea Ice (Manitounuk Sound, Hudson Bay)

1981 ◽  
Vol 38 (11) ◽  
pp. 1385-1392 ◽  
Author(s):  
L. Legendre ◽  
R. G. Ingram ◽  
M. Poulin
Keyword(s):  
Surface Water ◽  
Sea Ice ◽  
Water Column ◽  
Phytoplankton Bloom ◽  
Phytoplankton Production ◽  
Hudson Bay ◽  
Ice Algae ◽  
Phytoplankton Blooms ◽  
Low Salinity ◽  
Light Utilization

In polar and subpolar seas, there are numerous accounts of phytoplankton blooms in the upper water column under the ice. Various mechanisms have been invoked to explain these blooms: the seeding of the underlying surface water by algal cells (epontic flora) released from the melting ice, the optimization of light utilization by the cells, and the stabilization of the upper water column by the low-salinity melting water. From studies conducted in Manitounuk Sound (Hudson Bay), it is proposed that phytoplankton blooms under the ice probably result from the simultaneous deepening of both the photic layer (seasonal light increase) and the stratified layer (low-salinity melting water). In ice-covered seas, the release of ice algae superimposes itself on the phytoplankton bloom, resulting in the observed algal increase under melting ice.Key words: phytoplankton, under-ice blooms, ice flora, stability, nutrients, Hudson Bay

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