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  • 2020-2023  (2)
  • 2010-2014  (113)
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  • 1
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    Holocene variability in sea‐ice conditions in the eastern Baffin Bay‐Labrador Sea – A north–south biomarker transect study (2022)
    Saini, Jeetendra ; Stein, Ruediger ; Fahl, Kirsten ; [et al.]
    Details
    Publication Date: 2022-10-05
    Description: Reconstructions of sea‐surface conditions during the Holocene were achieved using three sediment cores from northeastern Baffin Bay (GeoB19948‐3 and GeoB19927‐3) and the Labrador Sea (GeoB19905‐1) along a north–south transect based on sea‐ice IP25 and open‐water phytoplankton biomarkers (brassicasterol, dinosterol and HBI III). In Baffin Bay, sea‐surface conditions in the Early Holocene were characterized by extended (early) spring sea ice cover (SIC) prior to 7.6 ka BP. The conditions in the NE Labrador Sea, however, remained predominantly ice‐free in spring/autumn due to the enhanced influx of Atlantic Water (West Greenland Current, WGC) from 11.5 until ~9.1 ka BP, succeeded by a period of continued (spring–autumn) ice‐free conditions between 9.1 and 7.6 ka BP corresponding to the onset of Holocene Thermal Maximum (HTM)‐like conditions. A transition towards reoccurring ice‐edge and significantly reduced SIC conditions in Baffin Bay is evident in the Middle Holocene (~7.6–3 ka BP) probably caused by the variations in the WGC influence associated with the ice melting and can be characterized as HTM‐like conditions. These HTM‐like conditions are predominantly recorded in the NE Labrador Sea area shown by (spring–autumn) ice‐free conditions from 5.9–3 ka BP. In the Late Holocene (last ~3 ka), our combined proxy records from eastern Baffin Bay indicate low in‐situ ice algae production; however, enhanced multi‐year (drifted) sea ice in this area was possibly attributed to the increased influx of Polar Water mass influx and may correlate with the Neoglacial cooling. The conditions in the NE Labrador Sea during the last 3 ka, however, continued to remain (spring–autumn) ice‐free. Our data from the Baffin Bay–Labrador Sea transect suggest a dominant influence of meltwater influx on sea‐ice formation throughout the Holocene, in contrast to sea‐ice records from the Fram Strait area, which seem to follow predominantly the summer insolation trend.
    Description: image
    Description: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:551.46
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 2
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    Rapid shifts in subarctic Pacific climate between 138 and 70 ka (2014)
    GSA, Geological Society of America
    In:  Geology, 42 (10). pp. 899-902.
    Details
    Publication Date: 2019-09-23
    Description: During the past decades, remarkable changes in sea-surface temperature (SST) and sea-ice extent have been observed in the marginal seas of the subarctic Pacific. However, little is known about natural climate variability at millennial time scales far beyond instrumental observations. Geological proxy records, such as those derived from marine sediments, offer a unique opportunity to investigate millennial-scale natural climate variability of the Artic and subarctic environments during past glacial-interglacial cycles. Here we provide reconstructions of sea-ice variability inferred from IP25 (Ice Proxy with 25 carbon atoms) sea-ice biomarker and SST fluctuations based on alkenone unsaturation index (Graphic) of the subarctic Pacific realm between 138 and 70 ka. Warmest sea-surface conditions were found during the early Eemian interglacial (128 to 126 ka), exceeding modern SSTs by ∼2 °C. The further North Pacific climate evolution is marked by pronounced oscillations in SST and sea-ice extent on millennial time scales, which correspond remarkably well to short-term temperature oscillations known from Greenland and the North Atlantic. These results imply a common forcing, which seems to be closely coupled to dynamics of the Atlantic meridional overturning circulation. However, immediate propagation of such climate fluctuations far beyond the North Atlantic basin suggests a rapid circumpolar coupling mechanism probably acting through the atmosphere, a prerequisite to explain the apparent synchronicity of remote climatic reorganizations in the subarctic Pacific.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1130/G35879.1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Last interglacial surface water structure in the western Mediterranean (Balearic) Sea: Climatic variability and link between low and high latitudes (2014)
    Elsevier
    In:  Global and Planetary Change, 123 . pp. 67-76.
    Details
    Publication Date: 2019-09-23
    Description: Highlights • Climate progression in the Balearic basin is examined between 140 and 100 ka. • A number of MIS 5e intra-interglacial cooling events is recognized. • MIS 5e climate phasing in the Western Mediterranean resembles the one in the Nordic Seas. • Foraminiferal abundances are strongly tied to a water circulation regime. • The timing of ORL deposition during MIS 5e resembles that of during the Holocene. Abstract A multiproxy analysis based on planktic foraminiferal abundances, derived SSTs, and stable planktic isotopes measurements together with alkenone abundances and Uk′37 SSTs was performed on late MIS 6 to early MIS 5d sediment recovered from Site 975 (ODP Leg 161) in the South Balearic Islands Basin (Western Mediterranean) with emphasis on reconstructing the climate progression of the last interglacial period. A number of abrupt climate changes related to alternative influence of nutrient rich northern and oligotrophic southern water masses was revealed. Heinrich event 11 and cooling events C27, C26, C25, C24, and C23, which have been previously described in the North Atlantic, were recognized. However, in comparison to the eastern North Atlantic mid-latitude region, events C27 and C26 at Site 975 seem to be significantly more pronounced. Together with evidence of a two-phase climate optimum with maximum SSTs reached during its later phase, this implies a close similarity in climate dynamics between the Western Mediterranean and the Nordic seas. We propose that postglacial effects in the Nordic seas had an influence on the western Mediterranean climate via atmospheric circulation and that these effects competed with the insolation force.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.gloplacha.2014.10.004
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Biomarker distributions in surface sediments from the Kara and Laptev seas (Arctic Ocean): indicators for organic-carbon sources and sea-ice coverage (2013)
    Elsevier
    In:  Quaternary Science Reviews, 79 . pp. 40-52.
    Details
    Publication Date: 2014-08-29
    Description: Studies of spatial and temporal changes in modern and past sea-ice occurrence may help to understand the processes controlling the recent decrease in Arctic sea-ice cover. Here, we determined concentrations of IP25, a novel biomarker proxy for sea ice developed in recent years, phytoplankton-derived biomarkers (brassicasterol and dinosterol) and terrigenous biomarkers (campesterol and β-sitosterol) in the surface sediments from the Kara and Laptev seas to estimate modern spatial (seasonal) sea-ice variability and organic-matter sources. C25-HBI dienes and trienes were determined as additional palaeoenvironmental proxies in the study area. Furthermore, a combined phytoplankton-IP25 biomarker approach (PIP25 index) is used to reconstruct the modern sea-ice distribution more quantitatively. The terrigenous biomarkers reach maximum concentrations in the coastal zones and estuaries, reflecting the huge discharge by the major rivers Ob, Yenisei and Lena. Maxima in phytoplankton biomarkers indicating increased primary productivity were found in the seasonally ice-free central part of the Kara and Laptev seas. Neither IP25 nor PIP25, however, shows a clear and simple correlation with satellite sea-ice distribution in our study area due to the complex environmental conditions in our study area and the transportation process of sea-ice diatom in the water column. Differences in the diene/IP25 and triene/IP25 ratios point to different sources of these HBIs and different environmental conditions. The diene/IP25 ratio seems to correlate positively with sea-surface temperature, while negatively with salinity distributions.
    Type: Article , PeerReviewed
    DOI: 10.1016/j.quascirev.2012.11.028
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    The meridional temperature gradient in the eastern North Atlantic during MIS 11 and its link to the ocean–atmosphere system (2012)
    Elsevier
    In:  Palaeogeography, Palaeoclimatology, Palaeoecology, 333/334 . pp. 24-39.
    Details
    Publication Date: 2019-09-23
    Description: Temporal and spatial patterns in eastern North Atlantic sea-surface temperatures (SST) were reconstructed for marine isotope stage (MIS) 11c using a submeridional transect of five sediment cores. The SST reconstructions are based on planktic foraminiferal abundances and alkenone indices, and are supported by benthic and planktic stable isotope measurements, as well as by ice-rafted debris content in polar and middle latitudes. Additionally, the larger-scale dynamics of the precipitation regime over northern Africa and the western Mediterranean region was evaluated from iron concentrations in marine sediments off NW Africa and planktic δ13C in combination with analysis of planktic foraminiferal abundances down to the species level in the Mediterranean Sea. Compared to the modern situation, it is revealed that during entire MIS 11c sensu stricto (ss), i.e., between 420 and 398 ka according to our age models, a cold SST anomaly in the Nordic seas co-existed with a warm SST anomaly in the middle latitudes and the subtropics, resulting in steeper meridional SST gradients than during the Holocene. Such a SST pattern correlates well with a prevalence of a negative mode of the modern North Atlantic Oscillation. We suggest that our scenario might partly explain the longer duration of wet conditions in the northern Africa during MIS 11c compared to the Holocene.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.palaeo.2012.03.005
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Last interglacial surface water structure in the NW Mediterranean (Balearic) Sea : climatic variability and link between low and high latitudes (2014)
    GeoUnion Alfred-Wegener-Stiftung
    In:  [Poster] In: international REKLIM Conference “Our Climate – Our Future, Regional Perspectives on a Global Challenge” , 06.10.-09.10.2014, Berlin . Our Climate – Our Future : Regional Perspectives on a Global Challenge ; International REKLIM Conference, 6 - 9 October, 2014, Umweltforum Auferstehungskirche, Berlin, Germany ; Program and Abstracts / REKLIM, Helmholtzverbund Regionale Klimaänderungen ; Helmholtz Association ; p. 120 .
    Details
    Publication Date: 2019-09-23
    Description: A multi-proxy analysis based on planktic foraminiferal abundances and derived SSTs, abundances of alkenone compounds and alkenone SSTs as well as stable isotopes measurements was performed for Site 975 (ODP Leg 161) from the slope of the South Balearic-Islands basin (Western Mediterranean) across late MIS 6 to early MIS 5d periods with emphasis on the climate progression of the last inter-glacial period. A number of abrupt climate changes related to alternative influence of northern nutrient rich and southern oligotrophic water masses were revealed. Among climate fluctuations, Heinrich Event 11 and cooling events C 27, C 26, C 25, C 24, C23 which had been detected earlier in the North Atlantic, were recognised. However, in comparison to the eastern North Atlantic mid-latitude region, at Site 975 events C27 and C26 seem to be significantly more pronounced. This fact along with evidence of two-phase climate optimum with the SSTs maximum reached during its later phase implies close similarity in climate dynamics between the Western Mediterranean and the Nordic Seas. It is proposed that postglacial effects in the Nordic Seas had an influence on the western Mediterranean climate via atmospheric circulation and competed with the insolation effect.
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Poster
  • 7
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    Cross-latitudinal climate teleconnections during the last interglacial (2014)
    In:  [Poster] In: AGU Fall Meeting 2014, 15.12.-19.12.2014, San Francisco, California, USA .
    Details
    Publication Date: 2019-09-23
    Description: PP33C-1256 A series of climate interruptions have been noted around the last warm period (MIS5e). Some of these are particularly conspicuous and occurred during both the deglacial as well as the glacial onset. These events are often associated with iceberg/meltwater charges into the subpolar/polar North Atlantic. A new multiproxy analysis using planktic foraminiferal abundances and SSTs, abundances of alkenone compounds and alkenone SSTs, and stable O/C isotope measurements was performed for Site 975 (Balearic Basin; Western Mediterranean). Samples covered the time from late MIS 6 to early MIS 5d with emphasis on the climate progression of the last interglacial period. A number of abrupt climate changes related to alternating influence of northern nutrient rich and southern oligotrophic water masses was revealed. Among the climate fluctuations, North Atlantic events Heinrich 11 as well as cooling events C27 – C23 could all be identified. However, in comparison to the eastern North Atlantic mid-latitude region, at Site 975 events C27 and C26 seem to be significantly more pronounced. This fact, along with evidence of a two-phase climate optimum with the SST maximum reached during its later phase, implies close similarity in climate dynamics between the Western Mediterranean and the polar Nordic Seas. It is therefore proposed that the postglacial marine development in the Nordic Seas – for instance, due to presence of winter sea ice – had a strong impact on the western Mediterranean climate via meridional atmospheric circulation patterns and temperature gradients.
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Poster
  • 8
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    Holocene cooling culminates in sea ice oscillations in Fram Strait (2012)
    Elsevier
    In:  Quaternary Science Reviews, 47 . pp. 1-14.
    Details
    Publication Date: 2019-09-23
    Description: A reconstruction of Holocene sea ice conditions in the Fram Strait provides insight into the palaeoenvironmental and palaeoceanographic development of this climate sensitive area during the past 8500 years BP. Organic geochemical analyses of sediment cores from eastern and western Fram Strait enable the identification of variations in the ice coverage that can be linked to changes in the oceanic (and atmospheric) circulation system. By means of the sea ice proxy IP25, phytoplankton-derived biomarkers and ice rafted detritus (IRD) increasing sea ice occurrences are traced along the western continental margin of Spitsbergen throughout the Holocene, which supports previous palaeoenvironmental reconstructions that document a general cooling. A further significant ice advance during the Neoglacial is accompanied by distinct sea ice fluctuations, which point to short-term perturbations in either the Atlantic Water advection or Arctic Water outflow at this site. At the continental shelf of East Greenland, the general Holocene cooling, however, seems to be less pronounced and sea ice conditions remained rather stable. Here, a major Neoglacial increase in sea ice coverage did not occur before 1000 years BP. Phytoplankton-IP25 indices (“PIP25-Index”) are used for more explicit sea ice estimates and display a Mid Holocene shift from a minor sea ice coverage to stable ice margin conditions in eastern Fram Strait, while the inner East Greenland shelf experienced less severe to marginal sea ice occurrences throughout the entire Holocene. Highlights ► Biomarker and IRD data give insight into Holocene sea ice conditions in Fram Strait. ► We find increasing sea ice coverage off West Spitsbergen throughout the Holocene. ► Oceanic/atmospheric variability caused Neoglacial sea ice fluctuations. ► Ice conditions along East Greenland shelf remain rather stable until 1000 years BP.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.quascirev.2012.04.024
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Sea surface temperature variability and sea-ice extent in the subarctic northwest Pacific during the past 15,000 years (2012)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 27 (3). PA3213.
    Details
    Publication Date: 2019-09-23
    Description: Past changes in North Pacific sea surface temperatures and sea-ice conditions are proposed to play a crucial role in deglacial climate development and ocean circulation but are less well known than from the North Atlantic. Here, we present new alkenone-based sea surface temperature records from the subarctic northwest Pacific and its marginal seas (Bering Sea and Sea of Okhotsk) for the time interval of the last 15 kyr, indicating millennial-scale sea surface temperature fluctuations similar to short-term deglacial climate oscillations known from Greenland ice-core records. Past changes in sea-ice distribution are derived from relative percentage of specific diatom groups and qualitative assessment of the IP25 biomarker related to sea-ice diatoms. The deglacial variability in sea-ice extent matches the sea surface temperature fluctuations. These fluctuations suggest a linkage to deglacial variations in Atlantic meridional overturning circulation and a close atmospheric coupling between the North Pacific and North Atlantic. During the Holocene the subarctic North Pacific is marked by complex sea surface temperature trends, which do not support the hypothesis of a Holocene seesaw in temperature development between the North Atlantic and the North Pacific. Key Points: - Millennial-scale changes in SST in the North Pacific during the last 15 kyr - Changes in sea-ice extent suggest a close coupling to SST fluctuations - Middle to late Holocene SSTs show no clear SST trend in the North Pacific
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2012PA002292
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Organic geochemical parameters (biomarker) in sediment trap PS2756-1 (2012)
    PANGAEA
    Details
    Publication Date: 2023-03-16
    Keywords: 2,6,10,14-Tetramethyl-7-(3-methylpent-4-enyl)pentadecane, flux; 24-Methylcholesta-5,22E-dien-3beta-ol, flux; Arctic Ocean; ARK-XI/1; AWI_Paleo; Calculated; DATE/TIME; Date/time end; DEPTH, water; Duration, number of days; Gas chromatography - Mass spectrometry (GC-MS); Mooring (long time); MOORY; Paleoenvironmental Reconstructions from Marine Sediments @ AWI; Phytoplankton biomarker Brassicasterol IP25 index; Polarstern; PS2756-1; PS36; PS36/051LOMO-2; Sample code/label
    Type: Dataset
    Format: text/tab-separated-values, 240 data points
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    DATA PANGAEA
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