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Geert-jan A. Brummer - One of the best experts on this subject based on the ideXlab platform.
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temporal offsets between surface temperature Ice Rafting and bottom flow speed proxies in the glacial mis 3 northern north atlantic
Quaternary Science Reviews, 2012Co-Authors: Lukas Jonkers, Matthias Moros, Maarten A. Prins, Gert Jan Weltje, S R Troelstra, Geert-jan A. BrummerAbstract:Rapid climatic switches during marine isotope stage 3 (29–59 ka BP) are often attributed to ocean circulation changes caused by freshwater input into the North Atlantic through the melting of large amounts of Icebergs and sea Ice. However, recent studies have questioned this direct coupling between factors influencing the ocean-climate system. By combining multiple proxies from two mid depth northern North Atlantic sediment cores we assess temporal offsets and links between freshwater input and response of the near bottom flow as well as between near bottom flow and sea surface temperatures changes. Grain size, mineralogical and magnetic proxies for Ice Rafting and near-bottom flow speed, interpreted as indicators of freshwater input and deep circulation strength, consistently indicate a delay in the recovery of the deep circulation after freshwater perturbations. Sea surface temperature variability is inferred from foraminiferal assemblages and Mg/Ca and δ18O of Neogloboquadrina pachyderma s. The records show rapid switches towards higher temperatures following the Ice-Rafting events. Interestingly, near sea surface temperatures increased and decreased again during periods of accelerating bottom flow speed, likely reflecting the sudden release of heat from deeper in the water column, rather than circulation changes. Our data thus confirm the impact of freshwater forcing on the Atlantic deep circulation, but suggest that temperature variability at the surface was not directly linked to these circulation changes.
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A reconstruction of sea surface warming in the northern North Atlantic during MIS 3 Ice-Rafting events
Quaternary Science Reviews, 2010Co-Authors: Lukas Jonkers, Matthias Moros, Maarten A. Prins, Trond Dokken, Carin Andersson Dahl, Noortje Dijkstra, Kerstin Perner, Geert-jan A. BrummerAbstract:Marine isotope stage 3 (29–59 kyr BP) is characterised by rapid shifts from cold stadial to warm interstadial periods, which may be linked to changes in the vigour of the Atlantic Meridional Overturning Circulation due to variable freshwater input by melting Ice. Here we present two northern North Atlantic multi-proxy records of sea surface conditions that indicate warm (near) sea surface conditions during such Ice-Rafting events. We infer near surface temperature from planktonic foraminiferal counts, Mg/Ca and oxygen isotopes of left-coiling Neogloboquadrina pachyderma and from calcite content. Temperatures increased during Ice-Rafting and rose rapidly to interstadial values after Ice-Rafting ceased. This pattern is clearest during Heinrich Event 4, but also present throughout the other millennial scale Ice-Rafting events. It indicates that stadials in the Greenland Ice-cores are concurrent with a (near) surface warming in the North Atlantic, which was probably restricted to the summer, as winter temperatures must have remained low for sediment-laden Ice to reach the site. As similar warming during Ice-Rafting events is seen regionally in the northern North Atlantic it cannot be explained by a rerouting of the North Atlantic Current. Rather, we attribute it to a shoaling of a warm subsurface water mass that was formed as a result of decreased ventilation of the upper waters and a continued northward subsurface flow of warm water. Planktonic carbon isotopes support this suggestion showing coincident decreased ventilation during deposition of Ice-rafted detritus (IRD). The absence of a clear meltwater spike in the δ18O records during IRD input suggests that besides glacial freshwater, sea Ice may have been responsible for the ventilation decrease and associated near surface heat built up. The proposed scenario is in agreement with modelling studies that require the release of heat trapped below the surface to restart the overturning circulation.
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A reconstruction of sea surface warming in the northern North Atlantic during MIS 3 Ice-Rafting events
Quaternary Science Reviews, 2010Co-Authors: Lukas Jonkers, Matthias Moros, Maarten A. Prins, Trond Dokken, Carin Andersson Dahl, Noortje Dijkstra, Kerstin Perner, Geert-jan A. BrummerAbstract:Marine isotope stage 3 (29-59 kyr BP) is characterised by rapid shifts from cold stadial to warm interstadial periods, which may be linked to changes in the vigour of the Atlantic Meridional Overturning Circulation due to variable freshwater input by melting Ice. Here we present two northern North Atlantic multi-proxy records of sea surface conditions that indicate warm (near) sea surface conditions during such Ice-Rafting events. We infer near surface temperature from planktonic foraminiferal counts, Mg/Ca and oxygen isotopes of left-coiling Neogloboquadrina pachyderma and from calcite content. Temperatures increased during Ice-Rafting and rose rapidly to interstadial values after Ice-Rafting ceased. This pattern is clearest during Heinrich Event 4, but also present throughout the other millennial scale Ice-Rafting events. It indicates that stadials in the Greenland Ice-cores are concurrent with a (near) surface warming in the North Atlantic, which was probably restricted to the summer, as winter temperatures must have remained low for sediment-laden Ice to reach the site. As similar warming during Ice-Rafting events is seen regionally in the northern North Atlantic it cannot be explained by a rerouting of the North Atlantic Current. Rather, we attribute it to a shoaling of a warm subsurface water mass that was formed as a result of decreased ventilation of the upper waters and a continued northward subsurface flow of warm water. Planktonic carbon isotopes support this suggestion showing coincident decreased ventilation during deposition of Ice-rafted detritus (IRD). The absence of a clear meltwater spike in the
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Transport of terrestrial organic matter to the deep North Atlantic Ocean by Ice Rafting
Organic Geochemistry, 2007Co-Authors: Stefan Schouten, Geert-jan A. Brummer, Jort Ossebaar, Henry Elderfield, Jaap S. Sinninghe DamstéAbstract:Abstract Total organic carbon (TOC), δ13C values of TOC (δ13Corg) and glycerol dialkyl glycerol tetraethers (GDGTs) were analysed for a sediment core from the North Atlantic covering the last 30 kyr to investigate organic matter deposition due to Ice Rafting. TOC content was low in sediments representing glacial times (0.2–0.4%) and even lower in Holocene sediments (
Matthias Moros - One of the best experts on this subject based on the ideXlab platform.
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temporal offsets between surface temperature Ice Rafting and bottom flow speed proxies in the glacial mis 3 northern north atlantic
Quaternary Science Reviews, 2012Co-Authors: Lukas Jonkers, Matthias Moros, Maarten A. Prins, Gert Jan Weltje, S R Troelstra, Geert-jan A. BrummerAbstract:Rapid climatic switches during marine isotope stage 3 (29–59 ka BP) are often attributed to ocean circulation changes caused by freshwater input into the North Atlantic through the melting of large amounts of Icebergs and sea Ice. However, recent studies have questioned this direct coupling between factors influencing the ocean-climate system. By combining multiple proxies from two mid depth northern North Atlantic sediment cores we assess temporal offsets and links between freshwater input and response of the near bottom flow as well as between near bottom flow and sea surface temperatures changes. Grain size, mineralogical and magnetic proxies for Ice Rafting and near-bottom flow speed, interpreted as indicators of freshwater input and deep circulation strength, consistently indicate a delay in the recovery of the deep circulation after freshwater perturbations. Sea surface temperature variability is inferred from foraminiferal assemblages and Mg/Ca and δ18O of Neogloboquadrina pachyderma s. The records show rapid switches towards higher temperatures following the Ice-Rafting events. Interestingly, near sea surface temperatures increased and decreased again during periods of accelerating bottom flow speed, likely reflecting the sudden release of heat from deeper in the water column, rather than circulation changes. Our data thus confirm the impact of freshwater forcing on the Atlantic deep circulation, but suggest that temperature variability at the surface was not directly linked to these circulation changes.
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A reconstruction of sea surface warming in the northern North Atlantic during MIS 3 Ice-Rafting events
Quaternary Science Reviews, 2010Co-Authors: Lukas Jonkers, Matthias Moros, Maarten A. Prins, Trond Dokken, Carin Andersson Dahl, Noortje Dijkstra, Kerstin Perner, Geert-jan A. BrummerAbstract:Marine isotope stage 3 (29–59 kyr BP) is characterised by rapid shifts from cold stadial to warm interstadial periods, which may be linked to changes in the vigour of the Atlantic Meridional Overturning Circulation due to variable freshwater input by melting Ice. Here we present two northern North Atlantic multi-proxy records of sea surface conditions that indicate warm (near) sea surface conditions during such Ice-Rafting events. We infer near surface temperature from planktonic foraminiferal counts, Mg/Ca and oxygen isotopes of left-coiling Neogloboquadrina pachyderma and from calcite content. Temperatures increased during Ice-Rafting and rose rapidly to interstadial values after Ice-Rafting ceased. This pattern is clearest during Heinrich Event 4, but also present throughout the other millennial scale Ice-Rafting events. It indicates that stadials in the Greenland Ice-cores are concurrent with a (near) surface warming in the North Atlantic, which was probably restricted to the summer, as winter temperatures must have remained low for sediment-laden Ice to reach the site. As similar warming during Ice-Rafting events is seen regionally in the northern North Atlantic it cannot be explained by a rerouting of the North Atlantic Current. Rather, we attribute it to a shoaling of a warm subsurface water mass that was formed as a result of decreased ventilation of the upper waters and a continued northward subsurface flow of warm water. Planktonic carbon isotopes support this suggestion showing coincident decreased ventilation during deposition of Ice-rafted detritus (IRD). The absence of a clear meltwater spike in the δ18O records during IRD input suggests that besides glacial freshwater, sea Ice may have been responsible for the ventilation decrease and associated near surface heat built up. The proposed scenario is in agreement with modelling studies that require the release of heat trapped below the surface to restart the overturning circulation.
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A reconstruction of sea surface warming in the northern North Atlantic during MIS 3 Ice-Rafting events
Quaternary Science Reviews, 2010Co-Authors: Lukas Jonkers, Matthias Moros, Maarten A. Prins, Trond Dokken, Carin Andersson Dahl, Noortje Dijkstra, Kerstin Perner, Geert-jan A. BrummerAbstract:Marine isotope stage 3 (29-59 kyr BP) is characterised by rapid shifts from cold stadial to warm interstadial periods, which may be linked to changes in the vigour of the Atlantic Meridional Overturning Circulation due to variable freshwater input by melting Ice. Here we present two northern North Atlantic multi-proxy records of sea surface conditions that indicate warm (near) sea surface conditions during such Ice-Rafting events. We infer near surface temperature from planktonic foraminiferal counts, Mg/Ca and oxygen isotopes of left-coiling Neogloboquadrina pachyderma and from calcite content. Temperatures increased during Ice-Rafting and rose rapidly to interstadial values after Ice-Rafting ceased. This pattern is clearest during Heinrich Event 4, but also present throughout the other millennial scale Ice-Rafting events. It indicates that stadials in the Greenland Ice-cores are concurrent with a (near) surface warming in the North Atlantic, which was probably restricted to the summer, as winter temperatures must have remained low for sediment-laden Ice to reach the site. As similar warming during Ice-Rafting events is seen regionally in the northern North Atlantic it cannot be explained by a rerouting of the North Atlantic Current. Rather, we attribute it to a shoaling of a warm subsurface water mass that was formed as a result of decreased ventilation of the upper waters and a continued northward subsurface flow of warm water. Planktonic carbon isotopes support this suggestion showing coincident decreased ventilation during deposition of Ice-rafted detritus (IRD). The absence of a clear meltwater spike in the
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Sea surface temperatures and Ice Rafting in the Holocene North Atlantic: climate influences on northern Europe and Greenland
Quaternary Science Reviews, 2004Co-Authors: Matthias Moros, Kay Emeis, Bjørg Risebrobakken, Ian Snowball, Antoon Kuijpers, Jerry F. Mcmanus, Eystein JansenAbstract:Abstract The oceanographic conditions in the high-latitude North Atlantic ocean during the Holocene were reconstructed through analyses of sea surface temperature (SST; alkenone unsaturation ratios) and Ice Rafting (mineralogy and grain size) from two sediment sequences, one recovered from the Reykjanes Ridge at 59°N and the other from the Norwegian Sea at 68°N. Comparison of our records to published Ice core and terrestrial proxy-climate data sets suggests that atmospheric temperature changes over Northern Europe and Greenland were coupled to SST variability and Ice Rafting. The records outline four major climatic phases: (i) an early-Holocene Thermal Maximum that lasted until approximately 6.7 kyr BP, (ii) a distinctly cooler phase associated with increased Ice Rafting between 6.5 and 3.7 kyr BP, (iii) a transition to generally warmer, but relatively unstable climate conditions between 3.7 and 2 kyr BP and (iv) a second distinct SST decline that took place between 2 and 0.5 kyr BP. In contrast to the dominant control of Northern Hemisphere summer insolation on early-Holocene climate development (via strong seasonality), the trigger for the onset of relatively unstable climatic conditions in the North Atlantic at 3.7 kyr BP is not straightforward. However, it is possible that this change was triggered by late-Holocene winter insolation increase at high northern latitude and/or by inter-hemispheric changes in orbital forcing. The late-Holocene Neoglaciation trend, which is characteristic of numerous terrestrial archives in northern Europe, may not only be attributed to a gradual decrease in orbitally forced summer temperature, but also to increase snow precipitation at high northern latitudes during generally milder winters.
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Quartz content and the quartz-to-plagioclase ratio determined by X-ray diffraction: a proxy for Ice Rafting in the northern North Atlantic?
Earth and Planetary Science Letters, 2004Co-Authors: Matthias Moros, Trond Dokken, Tine L. Rasmussen, Ian Snowball, Antoon Kuijpers, Jerry F. Mcmanus, Troels F.d. Nielsen, Eystein JansenAbstract:Many paleoceanographic reconstructions of the glacial North Atlantic include estimates of Iceberg discharge, which are based on the variable abundance of Ice-rafted detritus (IRD) in deep-sea sediments. IRD abundance is most often determined by the mechanical separation and painstaking counting of terrigenous particles larger than a specified threshold grain size, typically 150 mum. Here we present a new proxy for IRD based on X-ray diffraction (XRD) analysis of bulk sediments. This approach complements results obtained from standard techniques while offering several distinct advantages. In addition to the rapid production of objective data, XRD measurements on bulk sediments are sensitive to a broader and more characteristic grain size range than counts of individual coarse lithic fragments. The technique is demonstrated in a study of 12 sediment cores from the North Atlantic. Bulk quartz content and the quartz-to-plagioclase ratio exhibit peak-to-peak correspondence to manual counting results, which verifies the identification of large IRD influxes. The XRD data also reveal variations between the manually identified peaks, suggesting increased sensitivity to low-level, distal, or sea-Ice sources of IRD. A saw-tooth pattern emerges in many IRD events, which supports a link between Ice Rafting and atmospheric temperature changes over Greenland, and providing further evidence of the influence of climate on Iceberg discharges. (C) 2003 Elsevier B.V. All rights reserved. (Less)
Lukas Jonkers - One of the best experts on this subject based on the ideXlab platform.
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temporal offsets between surface temperature Ice Rafting and bottom flow speed proxies in the glacial mis 3 northern north atlantic
Quaternary Science Reviews, 2012Co-Authors: Lukas Jonkers, Matthias Moros, Maarten A. Prins, Gert Jan Weltje, S R Troelstra, Geert-jan A. BrummerAbstract:Rapid climatic switches during marine isotope stage 3 (29–59 ka BP) are often attributed to ocean circulation changes caused by freshwater input into the North Atlantic through the melting of large amounts of Icebergs and sea Ice. However, recent studies have questioned this direct coupling between factors influencing the ocean-climate system. By combining multiple proxies from two mid depth northern North Atlantic sediment cores we assess temporal offsets and links between freshwater input and response of the near bottom flow as well as between near bottom flow and sea surface temperatures changes. Grain size, mineralogical and magnetic proxies for Ice Rafting and near-bottom flow speed, interpreted as indicators of freshwater input and deep circulation strength, consistently indicate a delay in the recovery of the deep circulation after freshwater perturbations. Sea surface temperature variability is inferred from foraminiferal assemblages and Mg/Ca and δ18O of Neogloboquadrina pachyderma s. The records show rapid switches towards higher temperatures following the Ice-Rafting events. Interestingly, near sea surface temperatures increased and decreased again during periods of accelerating bottom flow speed, likely reflecting the sudden release of heat from deeper in the water column, rather than circulation changes. Our data thus confirm the impact of freshwater forcing on the Atlantic deep circulation, but suggest that temperature variability at the surface was not directly linked to these circulation changes.
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A reconstruction of sea surface warming in the northern North Atlantic during MIS 3 Ice-Rafting events
Quaternary Science Reviews, 2010Co-Authors: Lukas Jonkers, Matthias Moros, Maarten A. Prins, Trond Dokken, Carin Andersson Dahl, Noortje Dijkstra, Kerstin Perner, Geert-jan A. BrummerAbstract:Marine isotope stage 3 (29–59 kyr BP) is characterised by rapid shifts from cold stadial to warm interstadial periods, which may be linked to changes in the vigour of the Atlantic Meridional Overturning Circulation due to variable freshwater input by melting Ice. Here we present two northern North Atlantic multi-proxy records of sea surface conditions that indicate warm (near) sea surface conditions during such Ice-Rafting events. We infer near surface temperature from planktonic foraminiferal counts, Mg/Ca and oxygen isotopes of left-coiling Neogloboquadrina pachyderma and from calcite content. Temperatures increased during Ice-Rafting and rose rapidly to interstadial values after Ice-Rafting ceased. This pattern is clearest during Heinrich Event 4, but also present throughout the other millennial scale Ice-Rafting events. It indicates that stadials in the Greenland Ice-cores are concurrent with a (near) surface warming in the North Atlantic, which was probably restricted to the summer, as winter temperatures must have remained low for sediment-laden Ice to reach the site. As similar warming during Ice-Rafting events is seen regionally in the northern North Atlantic it cannot be explained by a rerouting of the North Atlantic Current. Rather, we attribute it to a shoaling of a warm subsurface water mass that was formed as a result of decreased ventilation of the upper waters and a continued northward subsurface flow of warm water. Planktonic carbon isotopes support this suggestion showing coincident decreased ventilation during deposition of Ice-rafted detritus (IRD). The absence of a clear meltwater spike in the δ18O records during IRD input suggests that besides glacial freshwater, sea Ice may have been responsible for the ventilation decrease and associated near surface heat built up. The proposed scenario is in agreement with modelling studies that require the release of heat trapped below the surface to restart the overturning circulation.
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A reconstruction of sea surface warming in the northern North Atlantic during MIS 3 Ice-Rafting events
Quaternary Science Reviews, 2010Co-Authors: Lukas Jonkers, Matthias Moros, Maarten A. Prins, Trond Dokken, Carin Andersson Dahl, Noortje Dijkstra, Kerstin Perner, Geert-jan A. BrummerAbstract:Marine isotope stage 3 (29-59 kyr BP) is characterised by rapid shifts from cold stadial to warm interstadial periods, which may be linked to changes in the vigour of the Atlantic Meridional Overturning Circulation due to variable freshwater input by melting Ice. Here we present two northern North Atlantic multi-proxy records of sea surface conditions that indicate warm (near) sea surface conditions during such Ice-Rafting events. We infer near surface temperature from planktonic foraminiferal counts, Mg/Ca and oxygen isotopes of left-coiling Neogloboquadrina pachyderma and from calcite content. Temperatures increased during Ice-Rafting and rose rapidly to interstadial values after Ice-Rafting ceased. This pattern is clearest during Heinrich Event 4, but also present throughout the other millennial scale Ice-Rafting events. It indicates that stadials in the Greenland Ice-cores are concurrent with a (near) surface warming in the North Atlantic, which was probably restricted to the summer, as winter temperatures must have remained low for sediment-laden Ice to reach the site. As similar warming during Ice-Rafting events is seen regionally in the northern North Atlantic it cannot be explained by a rerouting of the North Atlantic Current. Rather, we attribute it to a shoaling of a warm subsurface water mass that was formed as a result of decreased ventilation of the upper waters and a continued northward subsurface flow of warm water. Planktonic carbon isotopes support this suggestion showing coincident decreased ventilation during deposition of Ice-rafted detritus (IRD). The absence of a clear meltwater spike in the
Eystein Jansen - One of the best experts on this subject based on the ideXlab platform.
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Sea surface temperatures and Ice Rafting in the Holocene North Atlantic: climate influences on northern Europe and Greenland
Quaternary Science Reviews, 2004Co-Authors: Matthias Moros, Kay Emeis, Bjørg Risebrobakken, Ian Snowball, Antoon Kuijpers, Jerry F. Mcmanus, Eystein JansenAbstract:Abstract The oceanographic conditions in the high-latitude North Atlantic ocean during the Holocene were reconstructed through analyses of sea surface temperature (SST; alkenone unsaturation ratios) and Ice Rafting (mineralogy and grain size) from two sediment sequences, one recovered from the Reykjanes Ridge at 59°N and the other from the Norwegian Sea at 68°N. Comparison of our records to published Ice core and terrestrial proxy-climate data sets suggests that atmospheric temperature changes over Northern Europe and Greenland were coupled to SST variability and Ice Rafting. The records outline four major climatic phases: (i) an early-Holocene Thermal Maximum that lasted until approximately 6.7 kyr BP, (ii) a distinctly cooler phase associated with increased Ice Rafting between 6.5 and 3.7 kyr BP, (iii) a transition to generally warmer, but relatively unstable climate conditions between 3.7 and 2 kyr BP and (iv) a second distinct SST decline that took place between 2 and 0.5 kyr BP. In contrast to the dominant control of Northern Hemisphere summer insolation on early-Holocene climate development (via strong seasonality), the trigger for the onset of relatively unstable climatic conditions in the North Atlantic at 3.7 kyr BP is not straightforward. However, it is possible that this change was triggered by late-Holocene winter insolation increase at high northern latitude and/or by inter-hemispheric changes in orbital forcing. The late-Holocene Neoglaciation trend, which is characteristic of numerous terrestrial archives in northern Europe, may not only be attributed to a gradual decrease in orbitally forced summer temperature, but also to increase snow precipitation at high northern latitudes during generally milder winters.
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Quartz content and the quartz-to-plagioclase ratio determined by X-ray diffraction: a proxy for Ice Rafting in the northern North Atlantic?
Earth and Planetary Science Letters, 2004Co-Authors: Matthias Moros, Trond Dokken, Tine L. Rasmussen, Ian Snowball, Antoon Kuijpers, Jerry F. Mcmanus, Troels F.d. Nielsen, Eystein JansenAbstract:Many paleoceanographic reconstructions of the glacial North Atlantic include estimates of Iceberg discharge, which are based on the variable abundance of Ice-rafted detritus (IRD) in deep-sea sediments. IRD abundance is most often determined by the mechanical separation and painstaking counting of terrigenous particles larger than a specified threshold grain size, typically 150 mum. Here we present a new proxy for IRD based on X-ray diffraction (XRD) analysis of bulk sediments. This approach complements results obtained from standard techniques while offering several distinct advantages. In addition to the rapid production of objective data, XRD measurements on bulk sediments are sensitive to a broader and more characteristic grain size range than counts of individual coarse lithic fragments. The technique is demonstrated in a study of 12 sediment cores from the North Atlantic. Bulk quartz content and the quartz-to-plagioclase ratio exhibit peak-to-peak correspondence to manual counting results, which verifies the identification of large IRD influxes. The XRD data also reveal variations between the manually identified peaks, suggesting increased sensitivity to low-level, distal, or sea-Ice sources of IRD. A saw-tooth pattern emerges in many IRD events, which supports a link between Ice Rafting and atmospheric temperature changes over Greenland, and providing further evidence of the influence of climate on Iceberg discharges. (C) 2003 Elsevier B.V. All rights reserved. (Less)
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Sea surface temperatures and Ice Rafting in the Holocene North Atlantic: climate influences on northern Europe and Greenland
Quaternary Science Reviews, 2004Co-Authors: Matthias Moros, Kay Emeis, Bjørg Risebrobakken, Ian Snowball, Antoon Kuijpers, Jerry Mcmanus, Eystein JansenAbstract:The oceanographic conditions in the high-latitude North Atlantic ocean during the Holocene were reconstructed through analyses of sea surface temperature (SST; alkenone unsaturation ratios) and Ice Rafting (mineralogy and grain size) from two sediment sequences, one recovered from the Reykjanes Ridge at 59degreesN and the other from the Norwegian Sea at 68degreesN. Comparison of our records to published Ice core and terrestrial proxy-climate data sets suggests that atmospheric temperature changes over Northern Europe and Greenland were coupled to SST variability and Ice Rafting. The records outline four major climatic phases: (i) an early-Holocene Thermal Maximum that lasted until approximately 6.7 kyr BP, (ii) a distinctly cooler phase associated with increased Ice Rafting between 6.5 and 3.7 kyr BP, (iii) a transition to generally warmer, but relatively unstable climate conditions between 3.7 and 2 kyr BP and (iv) a second distinct SST decline that took place between 2 and 0.5 kyr BP. In contrast to the dominant control of Northern Hemisphere summer insolation on early-Holocene climate development (via strong seasonality), the trigger for the onset of relatively unstable climatic conditions in the North Atlantic at 3.7 kyr BP is not straightforward. However, it is possible that this change was triggered by late-Holocene winter insolation increase at high northern latitude and/or by inter-hemispheric changes in orbital forcing. The late-Holocene Neoglaciation trend, which is characteristic of numerous terrestrial archives in northern Europe, may not only be attributed to a gradual decrease in orbitally forced summer temperature, but also to increase snow precipitation at high northern latitudes during generally milder winters. (C) 2004 Elsevier Ltd. All rights reserved
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pliocene pleistocene Ice Rafting history and cyclicity in the nordic seas during the last 3 5 myr
Paleoceanography, 2000Co-Authors: Eystein Jansen, Torben Fronval, Frank R Rack, James E T ChannellAbstract:A continuous 3.5 Myr IRD record was produced from Ocean Drilling Program (ODP) Site 907. A timescale based on magnetic polarity chrons, oxygen isotope stratigraphy (for the last 1Myr) and orbital tuning was developed. The record documents a stepwise inception of large-scale glacial cycles in the Nordic Seas region, the first being a marked expansion of the Greenland Ice sheet at 3.3 Ma. A second step occurred at 2.74 Ma by an expansion of large scale Ice sheets in the Northern Hemisphere. Ice sheet variability around the Nordic Seas was tightly coupled to global Ice volume over the past 3.3 Myr. Between 3 and 1 Ma, most of the variance of the IRD signal is in the 41 kyr band, whereas the last 1 Myr is characterized by stronger 100 kyr variance. The Gamma Ray Porosity Evaluator (GRAPE) density record is closely linked with IRD variations and documents sub orbital variability resembling the late Quaternary Heinrich/Bond cycles.
Maarten A. Prins - One of the best experts on this subject based on the ideXlab platform.
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temporal offsets between surface temperature Ice Rafting and bottom flow speed proxies in the glacial mis 3 northern north atlantic
Quaternary Science Reviews, 2012Co-Authors: Lukas Jonkers, Matthias Moros, Maarten A. Prins, Gert Jan Weltje, S R Troelstra, Geert-jan A. BrummerAbstract:Rapid climatic switches during marine isotope stage 3 (29–59 ka BP) are often attributed to ocean circulation changes caused by freshwater input into the North Atlantic through the melting of large amounts of Icebergs and sea Ice. However, recent studies have questioned this direct coupling between factors influencing the ocean-climate system. By combining multiple proxies from two mid depth northern North Atlantic sediment cores we assess temporal offsets and links between freshwater input and response of the near bottom flow as well as between near bottom flow and sea surface temperatures changes. Grain size, mineralogical and magnetic proxies for Ice Rafting and near-bottom flow speed, interpreted as indicators of freshwater input and deep circulation strength, consistently indicate a delay in the recovery of the deep circulation after freshwater perturbations. Sea surface temperature variability is inferred from foraminiferal assemblages and Mg/Ca and δ18O of Neogloboquadrina pachyderma s. The records show rapid switches towards higher temperatures following the Ice-Rafting events. Interestingly, near sea surface temperatures increased and decreased again during periods of accelerating bottom flow speed, likely reflecting the sudden release of heat from deeper in the water column, rather than circulation changes. Our data thus confirm the impact of freshwater forcing on the Atlantic deep circulation, but suggest that temperature variability at the surface was not directly linked to these circulation changes.
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A reconstruction of sea surface warming in the northern North Atlantic during MIS 3 Ice-Rafting events
Quaternary Science Reviews, 2010Co-Authors: Lukas Jonkers, Matthias Moros, Maarten A. Prins, Trond Dokken, Carin Andersson Dahl, Noortje Dijkstra, Kerstin Perner, Geert-jan A. BrummerAbstract:Marine isotope stage 3 (29–59 kyr BP) is characterised by rapid shifts from cold stadial to warm interstadial periods, which may be linked to changes in the vigour of the Atlantic Meridional Overturning Circulation due to variable freshwater input by melting Ice. Here we present two northern North Atlantic multi-proxy records of sea surface conditions that indicate warm (near) sea surface conditions during such Ice-Rafting events. We infer near surface temperature from planktonic foraminiferal counts, Mg/Ca and oxygen isotopes of left-coiling Neogloboquadrina pachyderma and from calcite content. Temperatures increased during Ice-Rafting and rose rapidly to interstadial values after Ice-Rafting ceased. This pattern is clearest during Heinrich Event 4, but also present throughout the other millennial scale Ice-Rafting events. It indicates that stadials in the Greenland Ice-cores are concurrent with a (near) surface warming in the North Atlantic, which was probably restricted to the summer, as winter temperatures must have remained low for sediment-laden Ice to reach the site. As similar warming during Ice-Rafting events is seen regionally in the northern North Atlantic it cannot be explained by a rerouting of the North Atlantic Current. Rather, we attribute it to a shoaling of a warm subsurface water mass that was formed as a result of decreased ventilation of the upper waters and a continued northward subsurface flow of warm water. Planktonic carbon isotopes support this suggestion showing coincident decreased ventilation during deposition of Ice-rafted detritus (IRD). The absence of a clear meltwater spike in the δ18O records during IRD input suggests that besides glacial freshwater, sea Ice may have been responsible for the ventilation decrease and associated near surface heat built up. The proposed scenario is in agreement with modelling studies that require the release of heat trapped below the surface to restart the overturning circulation.
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A reconstruction of sea surface warming in the northern North Atlantic during MIS 3 Ice-Rafting events
Quaternary Science Reviews, 2010Co-Authors: Lukas Jonkers, Matthias Moros, Maarten A. Prins, Trond Dokken, Carin Andersson Dahl, Noortje Dijkstra, Kerstin Perner, Geert-jan A. BrummerAbstract:Marine isotope stage 3 (29-59 kyr BP) is characterised by rapid shifts from cold stadial to warm interstadial periods, which may be linked to changes in the vigour of the Atlantic Meridional Overturning Circulation due to variable freshwater input by melting Ice. Here we present two northern North Atlantic multi-proxy records of sea surface conditions that indicate warm (near) sea surface conditions during such Ice-Rafting events. We infer near surface temperature from planktonic foraminiferal counts, Mg/Ca and oxygen isotopes of left-coiling Neogloboquadrina pachyderma and from calcite content. Temperatures increased during Ice-Rafting and rose rapidly to interstadial values after Ice-Rafting ceased. This pattern is clearest during Heinrich Event 4, but also present throughout the other millennial scale Ice-Rafting events. It indicates that stadials in the Greenland Ice-cores are concurrent with a (near) surface warming in the North Atlantic, which was probably restricted to the summer, as winter temperatures must have remained low for sediment-laden Ice to reach the site. As similar warming during Ice-Rafting events is seen regionally in the northern North Atlantic it cannot be explained by a rerouting of the North Atlantic Current. Rather, we attribute it to a shoaling of a warm subsurface water mass that was formed as a result of decreased ventilation of the upper waters and a continued northward subsurface flow of warm water. Planktonic carbon isotopes support this suggestion showing coincident decreased ventilation during deposition of Ice-rafted detritus (IRD). The absence of a clear meltwater spike in the
