Dinoflagellate cyst distribution in high-latitude marine environments and quantitative reconstruction of sea-surface salinity, temperature, and seasonality

1994 ◽  
Vol 31 (1) ◽  
pp. 48-62 ◽  
Author(s):  
Anne de Vernal ◽  
Jean-Louis Turon ◽  
Joel Guiot
Keyword(s):  
Sea Ice ◽  
High Latitude ◽  
Transfer Functions ◽  
Ice Cover ◽  
Sea Surface ◽  
Labrador Sea ◽  
Marine Environments ◽  
Long Distance ◽  
Surface Conditions ◽  
Dinoflagellate Cyst

A data base of 179 reference sites documents the relations between the assemblages of organic-walled dinoflagellate cysts and sea-surface temperature, salinity, and seasonality throughout the North Atlantic, adjacent subpolar basins (Labrador Sea, Baffin Bay, Irminger and Iceland basins) and epicontinental environments off eastern Canada (estuary and Gulf of St. Lawrence, Hudson Bay). Principal-component analyses show close relationships between dinoflagellate cyst data and sea-surface conditions: the first component (71.1% of the variance) correlates with the winter temperature, salinity, and seasonal duration of sea-ice cover, whereas the second component (11.3% of the variance) appears mainly related to summer temperature. Transfer functions using the best analogue method were tested by reconstructing modern sea-surface conditions on the basis of the reference dinoflagellate cyst assemblages. The correlation coefficient between instrumental averages and reconstructed values ranges from 0.87 (August temperature) to 0.97 (annual duration of sea-ice cover). These transfer functions appear most accurate for the reconstruction of sea-surface conditions in marginal marine environments of high-latitude basins. The only reservation concerns the validity of reconstruction in offshore regions characterized by low productivity where sparse cyst fluxes may result from long-distance transport through currents. The transfer functions that were applied in, as an example, a late Quaternary sequence of the Davis Strait in the northern Labrador Sea, notably suggest seasonal sea-ice cover extent of 6–10 months/year and August temperature and salinity of 1–4 °C and 31–33‰, respectively, during the last glacial optimum (isotopic stage 2).

Palynomorph distribution in Recent sediments from the Labrador Sea

1994 ◽  
Vol 31 (1) ◽  
pp. 115-127 ◽  
Author(s):  
André Rochon ◽  
Anne de Vernal
Keyword(s):  
Surface Water ◽  
Primary Productivity ◽  
Water Masses ◽  
Sea Surface ◽  
Labrador Sea ◽  
Dinoflagellate Cysts ◽  
Eastern Canada ◽  
Long Distance ◽  
Surface Conditions ◽  
Dinoflagellate Cyst

Surface sediments from the Labrador Sea and Baffin Bay have been examined for their palynomorph content. Pollen and spore assemblages reflect the vegetation zones of eastern Canada, although long-distance atmospheric transport results in over-representation of Pinus and spores. A linear decrease of pollen input is observed with distance from the source vegetation; the abyssal domain receives less than 2% of the initial input. The abundance of dinoflagellate cysts reflects a relatively high primary productivity in surface water masses which seems proportional to the benthic productivity, as shown by the concentrations of organic linings of foraminifers. The relative abundance of dinoflagellate cyst taxa and principal component analysis led to the definition of three assemblages that can be related to sea-surface conditions and current pattern. The modern distribution of dinoflagellate cysts was used to interpret assemblages recovered in five box cores from the deep Labrador Sea. Results reveal important changes in sea-surface conditions during the Holocene. At the end of the last glacial period, the productivity in surface waters was sparse, notably on the continental slope off southwest Greenland. Shortly after the deglaciation, the primary productivity increased, probably due to the improvement of sea-surface conditions. At about 5000 BP, the dinoflagellate cyst concentrations and fluxes reach maximum values, and the assemblages are marked by the augmentation of Nematosphaeropsis labyrinthus relative to Operculodinium centrocarpum. This trend is associated with a cooling and the increased influence of the inner component of the Greenland Current in surface water masses of the Labrador Sea. It marks the establishment of modern conditions in the basin.

Palynological evidence of sea-surface conditions in the Barents Sea off northeast Svalbard during the postglacial period

2020 ◽  
pp. 1-15
Author(s):  
Camille Brice ◽  
Anne de Vernal ◽  
Elena Ivanova ◽  
Simon van Bellen ◽  
Nicolas Van Nieuwenhove
Keyword(s):  
Sea Ice ◽  
Surface Waters ◽  
Barents Sea ◽  
Ice Cover ◽  
Atlantic Water ◽  
Transitional Period ◽  
Sea Surface ◽  
Sea Surface Salinity ◽  
Surface Conditions ◽  
The Barents Sea

Abstract Postglacial changes in sea-surface conditions, including sea-ice cover, summer temperature, salinity, and productivity were reconstructed from the analyses of dinocyst assemblages in core S2528 collected in the northwestern Barents Sea. The results show glaciomarine-type conditions until about 11,300 ± 300 cal yr BP and limited influence of Atlantic water at the surface into the Barents Sea possibly due to the proximity of the Svalbard-Barents Sea ice sheet. This was followed by a transitional period generally characterized by cold conditions with dense sea-ice cover and low-salinity pulses likely related to episodic freshwater or meltwater discharge, which lasted until 8700 ± 700 cal yr BP. The onset of “interglacial” conditions in surface waters was marked by a major change in dinocyst assemblages, from dominant heterotrophic to dominant phototrophic taxa. Until 4100 ± 150 cal yr BP, however, sea-surface conditions remained cold, while sea-surface salinity and sea-ice cover recorded large amplitude variations. By ~4000 cal yr BP optimum sea-surface temperature of up to 4°C in summer and maximum salinity of ~34 psu suggest enhanced influence of Atlantic water, and productivity reached up to 150 gC/m2/yr. After 2200 ± 1300 cal yr BP, a distinct cooling trend accompanied by sea-ice spreading characterized surface waters. Hence, during the Holocene, with exception of an interval spanning about 4000 to 2000 cal yr BP, the northern Barents Sea experienced harsh environments, relatively low productivity, and unstable conditions probably unsuitable for human settlements.

Palynological Evidence of Climatic and Oceanographic Changes in the North Sea during the Last Deglaciation

1998 ◽  
Vol 49 (2) ◽  
pp. 197-207 ◽  
Author(s):  
André Rochon ◽  
Anne de Vernal ◽  
Hans-Petter Sejrup ◽  
Haflidi Haflidason
Keyword(s):  
Sea Ice ◽  
North Sea ◽  
Surface Waters ◽  
Vegetation Cover ◽  
Younger Dryas ◽  
Late Glacial ◽  
Ice Cover ◽  
Sea Surface ◽  
Delayed Response ◽  
Surface Conditions

Palynological analyses performed on cores from the Norwegian Channel (Troll 8903) led to reconstruction of the late-glacial variations in sea-surface conditions using dinoflagellate cyst data and permitted direct correlation with the vegetation history of northwestern Europe derived from pollen assemblages. By ∼15,000 yr B.P., ice rapidly receded from the Norwegian shelf and relatively warm summer conditions prevailed in surface waters. A first late-glacial cooling marked by extensive seasonal sea–ice cover is dated at ca. 13,600–13,000 14C yr B.P., which coincides with the Oldest Dryas interval. During the Bølling–Allerød interval, a rise in sea-surface temperature both in February (up to 3°C) and August (up to 15°C) led to the establishment of ice-free conditions in the northern North Sea, while pollen data reveal a densification of the vegetation cover. The beginning of the Younger Dryas interval is marked by an increase in nonarboreal pollen input indicative of the opening of the forest vegetation cover, concomitant with a cooling of surface waters during winter and development of sea–ice cover. However, sea-surface conditions remained relatively warm in summer until about 10,300 yr B.P., when extremely cold conditions and extensive sea–ice cover developed (up to 7 months/yr). Improving conditions are recorded in surface waters by ∼10,100 yr B.P., a few hundred years before the development of forest cover onshore, as shown by the pollen record. Such a discrepancy between marine and terrestrial indicators at the end of Younger Dryas time suggests a delayed response of the vegetation to regional climate warming.

Organic-walled dinoflagellate cysts: Palynological tracers of sea-surface conditions in middle to high latitude marine environments

Geobios ◽  
1997 ◽  
Vol 30 (7) ◽  
pp. 905-920 ◽  
Author(s):  
Anne De Vernal ◽  
André Rochon ◽  
Jean-Louis Turon ◽  
Jens Matthiessen
Keyword(s):  
High Latitude ◽  
Sea Surface ◽  
Marine Environments ◽  
Dinoflagellate Cysts ◽  
Surface Conditions

Postglacial changes of terrestrial and marine environments along the Labrador coast: palynological evidence from cores 91-045-005 and 91-045-006, Cartwright Saddle

1997 ◽  
Vol 34 (10) ◽  
pp. 1358-1365 ◽  
Author(s):  
Elisabeth Levac ◽  
Anne de Vernal
Keyword(s):  
Forest Cover ◽  
Transfer Functions ◽  
Sea Surface ◽  
Surface Conditions ◽  
Dinoflagellate Cyst ◽  
Tree Migration ◽  
Tundra Vegetation ◽  
Arboreal Pollen ◽  
Shrub Tundra ◽  
Cover Up

The palynology of cores from Cartwright Saddle led to reconstruction of sea-surface conditions on the basis of transfer functions using dinoflagellate cyst assemblages, and to correlations with vegetational history on adjacent land as derived from pollen assemblages. From deglaciation to about 8000 BP, dinoflagellate cyst assemblages dominated by Algidasphaeridium? minutum indicate Arctic-type sea-surface conditions, and pollen assemblages reveal tundra vegetation in southeastern Labrador. Codominance of A.? minutum and Brigantedinium spp. indicate persistence of cold sea-surface conditions (August temperature < 3 °C) and extensive sea-ice cover (up to 11 months/year) until ca. 6000 BP. However, the occurrence of Abies, which reached a maximum abundance at ca. 7000–6000 BP, and increasing percentages of Alnus indicate northward tree migration and development of shrub tundra as a result of warmer terrestrial conditions. Around 6000 BP, the significant occurrence of Peridinium faeroense and Nematosphaeropsis labyrinthus suggests the establishment of modern-like conditions in surface waters. This transition coincides with an abrupt increase in the abundance of Picea, associated with the regional development of spruce forests. The later marine record does not indicate any significant trend in sea-surface temperature, whereas decreasing abundance of arboreal pollen reflects opening of the forest cover in response to a slight cooling onshore. Thus, palynological analyses suggest complex changes in continental climate and marine hydrography along the coast of Labrador.

Last Interglacial sea ice variability and paleoceanography of the Labrador Sea

2021 ◽  
Author(s):  
Kristine Steinsland ◽  
Ulysess Ninnemann ◽  
Kirsten Fahl ◽  
Rüdiger Stein ◽  
Danielle Grant ◽  
...  
Keyword(s):  
Sea Ice ◽  
Ocean Circulation ◽  
Thermohaline Circulation ◽  
Ice Cover ◽  
Sea Surface ◽  
Last Interglacial ◽  
Close Link ◽  
Large Variability ◽  
Dinoflagellate Cyst ◽  
Cooling Period

&lt;p&gt;Sea ice provides strong feedback in the climate system, and it plays an important role in modulating the strength of the Thermohaline Circulation through glacials, and even interglacials. The warmer than present Last Interglacial (LIG, ~116-128 ka) is thought to have a less stable climate than the current interglacial. Proxies from the deep- and surface subpolar North Atlantic Ocean show prominent instabilities pointing toward coupled ocean-climate variability.&amp;#160; Here we reconstruct sea surface and sea ice changes of the subpolar gyre through the penultimate deglaciation and LIG in order to evaluate sea ice&amp;#8217;s role as a driver and amplifier of these ocean circulation and climate changes. We reconstruct the sea ice and sea surface conditions using biomarkers (IP&lt;sub&gt;25&lt;/sub&gt;, sterols) and dinoflagellate cyst assemblages from the Eirik Drift. Low productivity combined with an absence of IP&lt;sub&gt;25&lt;/sub&gt; could indicate a potential full sea ice cover through MIS 6. The surface ocean experienced large variability through the first half of the LIG, including an early cooling with potential seasonal sea ice cover evident from the dinoflagellate cyst assemblage and IP&lt;sub&gt;25&lt;/sub&gt;. The peak warm period of the LIG is seen in the second half, followed by a brief cooling period towards the end. Following the LIG, MIS 5d is characterized by an IP&lt;sub&gt;25&lt;/sub&gt; signal and high relative abundances of round brown dinocysts indicating cooling with seasonal sea ice cover. Initial comparisons with deep ventilation proxies (benthic foraminiferal &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C data) indicate a potential close link between sea ice, surface hydrography and deep circulation. In future studies, we aim to compare the sea ice record to benthic foraminiferal &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C data from the same samples to better understand the connection between surface and deep-ocean variability.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

scholarly journals Connection between Sea Surface Anomalies and Atmospheric Quasi-Stationary Waves

2020 ◽  
Vol 33 (1) ◽  
pp. 201-212
Author(s):  
G. Wolf ◽  
A. Czaja ◽  
D. J. Brayshaw ◽  
N. P. Klingaman
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Southern Oscillation ◽  
Late Summer ◽  
Ice Cover ◽  
Sea Surface ◽  
Late Winter ◽  
Driving Mechanism ◽  
The North ◽  
The North Atlantic

AbstractLarge-scale, quasi-stationary atmospheric waves (QSWs) are known to be strongly connected with extreme events and general weather conditions. Yet, despite their importance, there is still a lack of understanding about what drives variability in QSW. This study is a step toward this goal, and it identifies three statistically significant connections between QSWs and sea surface anomalies (temperature and ice cover) by applying a maximum covariance analysis technique to reanalysis data (1979–2015). The two most dominant connections are linked to El Niño–Southern Oscillation and the North Atlantic Oscillation. They confirm the expected relationship between QSWs and anomalous surface conditions in the tropical Pacific and the North Atlantic, but they cannot be used to infer a driving mechanism or predictability from the sea surface temperature or the sea ice cover to the QSW. The third connection, in contrast, occurs between late winter to early spring Atlantic sea ice concentrations and anomalous QSW patterns in the following late summer to early autumn. This new finding offers a pathway for possible long-term predictability of late summer QSW occurrence.

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