Search

Marine Isotope Stage (MIS) 4 (ca. 71–57 ka; within the Middle Weichselian Substage) is considered a significant Pleistocene glaciation, but it remains poorly constrained in comparison to that of the Late Weichselian Last Glacial Maximum (LGM; ca. 29–19 ka, during MIS 2), or even the Late Saalian MIS 6 (ca. 190–130 ka). Most MIS 4 glacial landforms in Europe were erased by the more extensive LGM ice advance, precluding a robust reconstruction of its extent and dynamic through time. Marine sedimentary archives, in preserving the source-to-sink sediment transfer signals of ice-sheet and glacier processes, help to bridge this gap. Here, the signals west of the European Ice Sheet (EIS) are tracked for MIS 4 from the deep Bay of Biscay (NE Atlantic), which was the outlet for Fennoscandian Ice Sheet (FIS) sediment-laden meltwater during extensive glaciations, specifically when the British-Irish Ice Sheet (BIIS) and the FIS coalesced into the North Sea (as during MIS 6 and the LGM). Sedimentological, geochemical, and mineralogical proxies reveal the absence of FIS-derived material in Bay of Biscay sediment throughout MIS 4, which indicates that FIS meltwater and huge river systems from the North European Plain never drained into the Bay of Biscay at that time. This suggests that contrary to MIS 6 and the LGM, the BIIS and FIS were not likely large enough to coalesce and form a (grounded) ice bridge onto the North Sea, thus confirming geomorphic evidence for a significant, but relatively limited, glaciation in Europe during MIS 4. Closer to the Bay of Biscay, ice-marginal fluctuations of the BIIS are identified in the Celtic-Irish Sea region from the deep-sea record. More specifically, our findings suggest an early retreat of the Irish Sea Ice Stream as soon as ca. 68–65 ka, a few millennia before the demise of the EIS, and the Northern Hemisphere ice sheets as a whole, during Heinrich Stadial (HS) 6. This pattern is similar to that already recorded during MIS 2. Fi

Marine Isotope Stage (MIS) 4 (ca. 71–57 ka; within the Middle Weichselian Substage) is considered a significant Pleistocene glaciation, but it remains poorly constrained in comparison to that of the Late Weichselian Last Glacial Maximum (LGM; ca. 29–19 ka, during MIS 2), or even the Late Saalian MIS 6 (ca. 190–130 ka). Most MIS 4 glacial landforms in Europe were erased by the more extensive LGM ice advance, precluding a robust reconstruction of its extent and dynamic through time. Marine sedimentary archives, in preserving the source-to-sink sediment transfer signals of ice-sheet and glacier processes, help to bridge this gap. Here, the signals west of the European Ice Sheet (EIS) are tracked for MIS 4 from the deep Bay of Biscay (NE Atlantic), which was the outlet for Fennoscandian Ice Sheet (FIS) sediment-laden meltwater during extensive glaciations, specifically when the British-Irish Ice Sheet (BIIS) and the FIS coalesced into the North Sea (as during MIS 6 and the LGM). Sedimentological, geochemical, and mineralogical proxies reveal the absence of FIS-derived material in Bay of Biscay sediment throughout MIS 4, which indicates that FIS meltwater and huge river systems from the North European Plain never drained into the Bay of Biscay at that time. This suggests that contrary to MIS 6 and the LGM, the BIIS and FIS were not likely large enough to coalesce and form a (grounded) ice bridge onto the North Sea, thus confirming geomorphic evidence for a significant, but relatively limited, glaciation in Europe during MIS 4.Closer to the Bay of Biscay, ice-marginal fluctuations of the BIIS are identified in the Celtic-Irish Sea region from the deep-sea record. More specifically, our findings suggest an early retreat of the Irish Sea Ice Stream as soon as ca. 68–65 ka, a few millennia before the demise of the EIS, and the Northern Hemisphere ice sheets as a whole, during Heinrich Stadial (HS) 6. This pattern is similar to that already recorde

Rapid changes in ocean circulation and climate have been observed in marine-sediment and ice cores over the last glacial period and deglaciation, highlighting the non-linear character of the climate system and underlining the possibility of rapid climate shifts in response to anthropogenic greenhouse gas forcing. To date, these rapid changes in climate and ocean circulation are still not fully explained. One obstacle hindering progress in our understanding of the interactions between past ocean circulation and climate changes is the difficulty of accurately dating marine cores. Here, we present a set of 92 marine sediment cores from the Atlantic Ocean for which we have established age-depth models that are consistent with the Greenland GICC05 ice core chronology, and computed the associated dating uncertainties, using a new deposition modeling technique. This is the first set of consistently dated marine sediment cores enabling paleoclimate scientists to evaluate leads/lags between circulation and climate changes over vast regions of the Atlantic Ocean. Moreover, this data set is of direct use in paleoclimate modeling studies.

Producing independent and accurate chronologies for marine sediments is a prerequisite to understand the sequence of millennial-scale events and reveal potential temporal offsets between marine and continental records, or between different marine records, possibly from different regions. The last 40 ky is a generally well-constrained period since radiocarbon (14C) can be used as an absolute dating tool. However, in the northern North Atlantic, calendar ages cannot be directly derived from 14C ages, due to temporal and spatial variations of surface reservoir ages. Alternatively, chronologies can be derived by aligning Greenland ice-core time series with marine surface records. Yet this approach suffers from the lack of clearly defined climatic events between 14.7 and 23.3 cal ky BP (hereafter ka), a crucial period encompassing Heinrich Stadial 1 and the onset of the last deglaciation. In this study, (i) we assess the benefits of 230Th normalization to refine the sedimentation history between surface temperature alignment tie points and (ii) revisit the chronologies of three North Atlantic marine records. Our study supports the contention that the marked increase in the Greenland Ca2+ record at 17.48 ka ± 0.21 ky (1σ) occurred within dating uncertainty of sea surface temperature cooling in the North Atlantic at the onset of Heinrich Stadial 1. This sharp feature might be useful for future chronostratigraphic alignments to remedy the lack of chronological constraint between 14.7 and 23.3 ka for North Atlantic marine records that are subject to large changes in 14C surface reservoir age.

The last glacial period was punctuated by abrupt climatic events with extrema known as Heinrich and Dansgaard–Oeschger events. These millennial events have been the subject of many paleoreconstructions and model experiments in the past decades, but yet the hydrological processes involved remain elusive. In the present work, high-resolution analyses were conducted on the 12–42 ka BP section of core MD99-2281 retrieved southwest of the Faeroe Islands, and combined with analyses conducted in two previous studies (Zumaque et al., 2012; Caulle et al., 2013). Such a multiproxy approach, coupling micropaleontological, geochemical and sedimentological analyses, allows us to track surface, subsurface, and deep hydrological processes occurring during these rapid climatic changes. Records indicate that the coldest episodes of the studied period (Greenland stadials and Heinrich stadials) were characterized by a strong stratification of surface waters. This surface stratification seems to have played a key role in the dynamics of subsurface and deep-water masses. Indeed, periods of high surface stratification are marked by a coupling of subsurface and deep circulations which sharply weaken at the beginning of stadials, while surface conditions progressively deteriorate throughout these cold episodes; conversely, periods of decreasing surface stratification (Greenland interstadials) are characterized by a coupling of surface and deep hydrological processes, with progressively milder surface conditions and gradual intensification of the deep circulation, while the vigor of the subsurface northward Atlantic flow remains constantly high. Our results also reveal different and atypical hydrological signatures during Heinrich stadials (HSs): while HS1 and HS4 exhibit a "usual" scheme with reduced overturning circulation, a relatively active North Atlantic circulation seems to have prevailed during HS2, and HS3 seems to have experienced a re-intensification of this circulation during th

The Sahara experienced several humid episodes during the late Quaternary, associated with the development of vast fluvial networks and enhanced freshwater delivery to the surrounding ocean margins. In particular, marine sediment records off Western Sahara indicate deposition of river-borne material at those times, implying sustained fluvial discharges along the West African margin. Today, however, no major river exists in this area; therefore, the origin of these sediments remains unclear. Here, using orbital radar satellite imagery, we present geomorphological data that reveal the existence of a large buried paleodrainage network on the Mauritanian coast. On the basis of evidence from the literature, we propose that reactivation of this major paleoriver during past humid periods contributed to the delivery of sediments to the Tropical Atlantic margin. This finding provides new insights for the interpretation of terrigenous sediment records off Western Africa, with important implications for our understanding of the paleohydrological history of the Sahara.

The last glacial period was punctuated by abrupt climatic events with extrema known as Heinrich and Dansgaard–Oeschger events. These millennial events have been the subject of many paleoreconstructions and model experiments in the past decades, but yet the hydrological processes involved remain elusive. In the present work, high-resolution analyses were conducted on the 12–42 ka BP section of core MD99-2281 retrieved southwest of the Faeroe Islands, and combined with analyses conducted in two previous studies (Zumaque et al., 2012; Caulle et al., 2013). Such a multiproxy approach, coupling micropaleontological, geochemical and sedimentological analyses, allows us to track surface, subsurface, and deep hydrological processes occurring during these rapid climatic changes. Records indicate that the coldest episodes of the studied period (Greenland stadials and Heinrich stadials) were characterized by a strong stratification of surface waters. This surface stratification seems to have played a key role in the dynamics of subsurface and deep-water masses. Indeed, periods of high surface stratification are marked by a coupling of subsurface and deep circulations which sharply weaken at the beginning of stadials, while surface conditions progressively deteriorate throughout these cold episodes; conversely, periods of decreasing surface stratification (Greenland interstadials) are characterized by a coupling of surface and deep hydrological processes, with progressively milder surface conditions and gradual intensification of the deep circulation, while the vigor of the subsurface northward Atlantic flow remains constantly high. Our results also reveal different and atypical hydrological signatures during Heinrich stadials (HSs): while HS1 and HS4 exhibit a "usual" scheme with reduced overturning circulation, a relatively active North Atlantic circulation seems to have prevailed during HS2, and HS3 seems to have experienced a re-intensification of this circulation during th

The Sahara experienced several humid episodes during the late Quaternary, associated with the development of vast fluvial networks and enhanced freshwater delivery to the surrounding ocean margins. In particular, marine sediment records off Western Sahara indicate deposition of river-borne material at those times, implying sustained fluvial discharges along the West African margin. Today, however, no major river exists in this area; therefore, the origin of these sediments remains unclear. Here, using orbital radar satellite imagery, we present geomorphological data that reveal the existence of a large buried paleodrainage network on the Mauritanian coast. On the basis of evidence from the literature, we propose that reactivation of this major paleoriver during past humid periods contributed to the delivery of sediments to the Tropical Atlantic margin. This finding provides new insights for the interpretation of terrigenous sediment records off Western Africa, with important implications for our understanding of the paleohydrological history of the Sahara.

The last glacial period was punctuated by abrupt climatic events with extrema known as Heinrich and Dansgaard–Oeschger events. These millennial events have been the subject of many paleoreconstructions and model experiments in the past decades, but yet the hydrological processes involved remain elusive. In the present work, high-resolution analyses were conducted on the 12–42 ka BP section of core MD99-2281 retrieved southwest of the Faeroe Islands, and combined with analyses conducted in two previous studies (Zumaque et al., 2012; Caulle et al., 2013). Such a multiproxy approach, coupling micropaleontological, geochemical and sedimentological analyses, allows us to track surface, subsurface, and deep hydrological processes occurring during these rapid climatic changes. Records indicate that the coldest episodes of the studied period (Greenland stadials and Heinrich stadials) were characterized by a strong stratification of surface waters. This surface stratification seems to have played a key role in the dynamics of subsurface and deep-water masses. Indeed, periods of high surface stratification are marked by a coupling of subsurface and deep circulations which sharply weaken at the beginning of stadials, while surface conditions progressively deteriorate throughout these cold episodes; conversely, periods of decreasing surface stratification (Greenland interstadials) are characterized by a coupling of surface and deep hydrological processes, with progressively milder surface conditions and gradual intensification of the deep circulation, while the vigor of the subsurface northward Atlantic flow remains constantly high. Our results also reveal different and atypical hydrological signatures during Heinrich stadials (HSs): while HS1 and HS4 exhibit a "usual" scheme with reduced overturning circulation, a relatively active North Atlantic circulation seems to have prevailed during HS2, and HS3 seems to have experienced a re-intensification of this circulation during th

The Sahara experienced several humid episodes during the late Quaternary, associated with the development of vast fluvial networks and enhanced freshwater delivery to the surrounding ocean margins. In particular, marine sediment records off Western Sahara indicate deposition of river-borne material at those times, implying sustained fluvial discharges along the West African margin. Today, however, no major river exists in this area; therefore, the origin of these sediments remains unclear. Here, using orbital radar satellite imagery, we present geomorphological data that reveal the existence of a large buried paleodrainage network on the Mauritanian coast. On the basis of evidence from the literature, we propose that reactivation of this major paleoriver during past humid periods contributed to the delivery of sediments to the Tropical Atlantic margin. This finding provides new insights for the interpretation of terrigenous sediment records off Western Africa, with important implications for our understanding of the paleohydrological history of the Sahara.

The last glacial period was punctuated by abrupt climatic events with extrema known as Heinrich and Dansgaard–Oeschger events. These millennial events have been the subject of many paleoreconstructions and model experiments in the past decades, but yet the hydrological processes involved remain elusive. In the present work, high-resolution analyses were conducted on the 12–42 ka BP section of core MD99-2281 retrieved southwest of the Faeroe Islands, and combined with analyses conducted in two previous studies (Zumaque et al., 2012; Caulle et al., 2013). Such a multiproxy approach, coupling micropaleontological, geochemical and sedimentological analyses, allows us to track surface, subsurface, and deep hydrological processes occurring during these rapid climatic changes. Records indicate that the coldest episodes of the studied period (Greenland stadials and Heinrich stadials) were characterized by a strong stratification of surface waters. This surface stratification seems to have played a key role in the dynamics of subsurface and deep-water masses. Indeed, periods of high surface stratification are marked by a coupling of subsurface and deep circulations which sharply weaken at the beginning of stadials, while surface conditions progressively deteriorate throughout these cold episodes; conversely, periods of decreasing surface stratification (Greenland interstadials) are characterized by a coupling of surface and deep hydrological processes, with progressively milder surface conditions and gradual intensification of the deep circulation, while the vigor of the subsurface northward Atlantic flow remains constantly high. Our results also reveal different and atypical hydrological signatures during Heinrich stadials (HSs): while HS1 and HS4 exhibit a "usual" scheme with reduced overturning circulation, a relatively active North Atlantic circulation seems to have prevailed during HS2, and HS3 seems to have experienced a re-intensification of this circulation during th

Glacial climate was characterised by two types of abrupt events. Greenland ice cores record Dansgaard–Oeschger events, marked by abrupt warming in-between cold, stadial phases. Six of these stadials appear related to major Heinrich events (HEs), identified from ice-rafted debris (IRD) and large excursions in carbon- and oxygen-stable isotopic ratios in North Atlantic deep sea sediments, documenting major ice sheet collapse events. This finding has led to the paradigm that glacial cold events are induced by the response of the Atlantic Meridional Overturning Circulation to such massive freshwater inputs, supported by sensitivity studies conducted with climate models of various complexities. These models also simulate synchronous Greenland temperature and lower-latitude hydrological changes.

Glacial climate was characterised by two types of abrupt events. Greenland ice cores record Dansgaard–Oeschger events, marked by abrupt warming in-between cold, stadial phases. Six of these stadials appear related to major Heinrich events (HEs), identified from ice-rafted debris (IRD) and large excursions in carbon- and oxygen-stable isotopic ratios in North Atlantic deep sea sediments, documenting major ice sheet collapse events. This finding has led to the paradigm that glacial cold events are induced by the response of the Atlantic Meridional Overturning Circulation to such massive freshwater inputs, supported by sensitivity studies conducted with climate models of various complexities. These models also simulate synchronous Greenland temperature and lower-latitude hydrological changes.

Glacial climate was characterised by two types of abrupt events. Greenland ice cores record Dansgaard–Oeschger events, marked by abrupt warming in-between cold, stadial phases. Six of these stadials appear related to major Heinrich events (HEs), identified from ice-rafted debris (IRD) and large excursions in carbon- and oxygen-stable isotopic ratios in North Atlantic deep sea sediments, documenting major ice sheet collapse events. This finding has led to the paradigm that glacial cold events are induced by the response of the Atlantic Meridional Overturning Circulation to such massive freshwater inputs, supported by sensitivity studies conducted with climate models of various complexities. These models also simulate synchronous Greenland temperature and lower-latitude hydrological changes.

Glacial climate was characterised by two types of abrupt events. Greenland ice cores record Dansgaard–Oeschger events, marked by abrupt warming in-between cold, stadial phases. Six of these stadials appear related to major Heinrich events (HEs), identified from ice-rafted debris (IRD) and large excursions in carbon- and oxygen-stable isotopic ratios in North Atlantic deep sea sediments, documenting major ice sheet collapse events. This finding has led to the paradigm that glacial cold events are induced by the response of the Atlantic Meridional Overturning Circulation to such massive freshwater inputs, supported by sensitivity studies conducted with climate models of various complexities. These models also simulate synchronous Greenland temperature and lower-latitude hydrological changes.

The monsoon is one of the most important climatic phenomena: it promotes inter-hemispheric exchange of energy and affects the economical prosperity of several countries exposed to its seasonal seesaw. Previous studies in both the Indian and Asian monsoon systems have generally suggested a dominant northern hemispheric (NH) control on summer monsoon dynamics at the scale of suborbital-millennial climatic changes, while the forcing/response of Indian and Asian monsoons at the orbital scale remains a matter of debate. Here, six marine sediment cores distributed across the whole Arabian Sea are used to build a regional surface marine productivity signal. The productivity signal is driven by the intensity of Indian summer monsoon winds. Our results demonstrate the existence of an imprint of suborbital southern hemispheric (SH) temperature changes (i.e. Antarctica) on the Indian summer monsoon during the last glacial period that is generally not recognized. During the last deglaciation, the NH played a more significant role. This suggests that fluctuations in the Indian monsoon are better explained in a bipolar context. The delta O-18 signal recorded in the Asian monsoon speleothem records could be exported by winds from the Indian summer monsoon region, as recently proposed in modelling exercise, explaining the SH signature observed in Asian cave speleothems. Contrary to the view of a passive response of Indian and Asian monsoons to NH anomalies, the present results appear to suggest that the Indo-Asian summer monsoon plays an active role in amplifying millennial inter-hemispheric asymmetric patterns. Additionally, this study confirms previously observed differences between Indian and Asian speleothem monsoonal records at the orbital-precession scale.

The monsoon is one of the most important climatic phenomena: it promotes inter-hemispheric exchange of energy and affects the economical prosperity of several countries exposed to its seasonal seesaw. Previous studies in both the Indian and Asian monsoon systems have generally suggested a dominant northern hemispheric (NH) control on summer monsoon dynamics at the scale of suborbital-millennial climatic changes, while the forcing/response of Indian and Asian monsoons at the orbital scale remains a matter of debate. Here, six marine sediment cores distributed across the whole Arabian Sea are used to build a regional surface marine productivity signal. The productivity signal is driven by the intensity of Indian summer monsoon winds. Our results demonstrate the existence of an imprint of suborbital southern hemispheric (SH) temperature changes (i.e. Antarctica) on the Indian summer monsoon during the last glacial period that is generally not recognized. During the last deglaciation, the NH played a more significant role. This suggests that fluctuations in the Indian monsoon are better explained in a bipolar context. The delta O-18 signal recorded in the Asian monsoon speleothem records could be exported by winds from the Indian summer monsoon region, as recently proposed in modelling exercise, explaining the SH signature observed in Asian cave speleothems. Contrary to the view of a passive response of Indian and Asian monsoons to NH anomalies, the present results appear to suggest that the Indo-Asian summer monsoon plays an active role in amplifying millennial inter-hemispheric asymmetric patterns. Additionally, this study confirms previously observed differences between Indian and Asian speleothem monsoonal records at the orbital-precession scale.

The last glacial period, showing the progressive development of large boreal ice sheets, was punctuated by large climatic excursions. These excursions were triggered mainly by atmosphereoceanice coupled dynamics and are thus exemplary case studies of natural climate variability. To characterize the sea-surface palaeohydrographical changes accompanying these oscillations along the European margin, we have integrated new palynological data (dinocysts) acquired on core MD99-2281 (60 degrees N, Faeroe Margin) during Marine Isotope Stage 2 in a latitudinal transect including published cores MD95-2002 (47 degrees N, Celtic Margin) and MD95-2010 (66 degrees N, Voring Plateau). This transect is superimposed on the modern North Atlantic Drift pathway, but also at the outskirts of glacial European ice sheets, thus ideally located to track sea-ice extent and ice-sheet instabilities through time. The results show a coherent and sensitive response of sea-surface environments to the complex chain of abrupt events that punctuated the end of the last glacial period. The Last Glacial Maximum was marked by large seasonal contrasts of temperatures, whereas Heinrich events (HE) were characterized by a sharp cooling and sea-ice development. A tripartite structure is identified within HE1, with indices of melting at 19k cal a BP, followed by a temperate phase synchronous of a relative stability of ice sheets, and a terminal phase (17.515k cal a BP) characteristic of the conventional Laurentian' HE1. Copyright (c) 2013 John Wiley & Sons, Ltd.

The monsoon is one of the most important climatic phenomena: it promotes inter-hemispheric exchange of energy and affects the economical prosperity of several countries exposed to its seasonal seesaw. Previous studies in both the Indian and Asian monsoon systems have generally suggested a dominant northern hemispheric (NH) control on summer monsoon dynamics at the scale of suborbital-millennial climatic changes, while the forcing/response of Indian and Asian monsoons at the orbital scale remains a matter of debate. Here, six marine sediment cores distributed across the whole Arabian Sea are used to build a regional surface marine productivity signal. The productivity signal is driven by the intensity of Indian summer monsoon winds. Our results demonstrate the existence of an imprint of suborbital southern hemispheric (SH) temperature changes (i.e. Antarctica) on the Indian summer monsoon during the last glacial period that is generally not recognized. During the last deglaciation, the NH played a more significant role. This suggests that fluctuations in the Indian monsoon are better explained in a bipolar context. The delta O-18 signal recorded in the Asian monsoon speleothem records could be exported by winds from the Indian summer monsoon region, as recently proposed in modelling exercise, explaining the SH signature observed in Asian cave speleothems. Contrary to the view of a passive response of Indian and Asian monsoons to NH anomalies, the present results appear to suggest that the Indo-Asian summer monsoon plays an active role in amplifying millennial inter-hemispheric asymmetric patterns. Additionally, this study confirms previously observed differences between Indian and Asian speleothem monsoonal records at the orbital-precession scale.

The last glacial period, showing the progressive development of large boreal ice sheets, was punctuated by large climatic excursions. These excursions were triggered mainly by atmosphereoceanice coupled dynamics and are thus exemplary case studies of natural climate variability. To characterize the sea-surface palaeohydrographical changes accompanying these oscillations along the European margin, we have integrated new palynological data (dinocysts) acquired on core MD99-2281 (60 degrees N, Faeroe Margin) during Marine Isotope Stage 2 in a latitudinal transect including published cores MD95-2002 (47 degrees N, Celtic Margin) and MD95-2010 (66 degrees N, Voring Plateau). This transect is superimposed on the modern North Atlantic Drift pathway, but also at the outskirts of glacial European ice sheets, thus ideally located to track sea-ice extent and ice-sheet instabilities through time. The results show a coherent and sensitive response of sea-surface environments to the complex chain of abrupt events that punctuated the end of the last glacial period. The Last Glacial Maximum was marked by large seasonal contrasts of temperatures, whereas Heinrich events (HE) were characterized by a sharp cooling and sea-ice development. A tripartite structure is identified within HE1, with indices of melting at 19k cal a BP, followed by a temperate phase synchronous of a relative stability of ice sheets, and a terminal phase (17.515k cal a BP) characteristic of the conventional Laurentian' HE1. Copyright (c) 2013 John Wiley & Sons, Ltd.

The monsoon is one of the most important climatic phenomena: it promotes inter-hemispheric exchange of energy and affects the economical prosperity of several countries exposed to its seasonal seesaw. Previous studies in both the Indian and Asian monsoon systems have generally suggested a dominant northern hemispheric (NH) control on summer monsoon dynamics at the scale of suborbital-millennial climatic changes, while the forcing/response of Indian and Asian monsoons at the orbital scale remains a matter of debate. Here, six marine sediment cores distributed across the whole Arabian Sea are used to build a regional surface marine productivity signal. The productivity signal is driven by the intensity of Indian summer monsoon winds. Our results demonstrate the existence of an imprint of suborbital southern hemispheric (SH) temperature changes (i.e. Antarctica) on the Indian summer monsoon during the last glacial period that is generally not recognized. During the last deglaciation, the NH played a more significant role. This suggests that fluctuations in the Indian monsoon are better explained in a bipolar context. The delta O-18 signal recorded in the Asian monsoon speleothem records could be exported by winds from the Indian summer monsoon region, as recently proposed in modelling exercise, explaining the SH signature observed in Asian cave speleothems. Contrary to the view of a passive response of Indian and Asian monsoons to NH anomalies, the present results appear to suggest that the Indo-Asian summer monsoon plays an active role in amplifying millennial inter-hemispheric asymmetric patterns. Additionally, this study confirms previously observed differences between Indian and Asian speleothem monsoonal records at the orbital-precession scale.

The rapid climatic variability characterising the Marine Isotopic Stage (MIS) 3 (~60–30 cal ka BP) provides key issues to understand the atmosphere–ocean–cryosphere dynamics. Here we investigate the response of sea-surface paleoenvironments to the MIS3 climatic variability through the study of a high resolution oceanic sedimentological archive (core MD99-2281, 60°21' N; 09°27' W; 1197 m water depth), retrieved during the MD114-IMAGES (International Marine Global Change Study) cruise from the southern part of the Faeroe Bank. This sector was under the proximal influence of European ice sheets (Fennoscandian Ice Sheet to the East, British Irish Ice Sheet to the South) during the last glacial and thus probably responded to the MIS3 pulsed climatic changes. We conducted a multi-proxy analysis of core MD99-2281, including magnetic properties, x-ray fluorescence measurements, characterisation of the coarse (>150 μm) lithic fraction (grain concentration) and the analysis of selected biogenic proxies (assemblages and stable isotope ratio of calcareous planktonic foraminifera, dinoflagellate cyst – e.g. dinocyst – assemblages). Results presented here are focussed on the dinocyst response, this proxy providing the reconstruction of past sea-surface hydrological conditions, qualitatively as well as quantitatively (e.g. transfer function sensu lato). Our study documents a very coherent and sensitive oceanic response to the MIS3 rapid climatic variability: strong fluctuations, matching those of stadial/interstadial climatic oscillations as depicted by Greenland ice cores, are recorded in the MD99-2281 archive. Proxies of terrigeneous and detritical material suggest increases in continental advection during Greenland Stadials (including Heinrich events), the latter corresponding also to southward migrations of polar waters. At the opposite, milder sea-surface conditions seem to develop during Greenland Interstadials. After 30 ka, reconstructed paleohydrological condit

The rapid climatic variability characterising the Marine Isotopic Stage (MIS) 3 (similar to 60-30 cal ka BP) provides key issues to understand the atmosphere-ocean-cryosphere dynamics. Here we investigate the response of sea-surface paleoenvironments to the MIS3 climatic variability through the study of a high resolution oceanic sedimentological archive (core MD99-2281, 60 degrees 21' N; 09 degrees 27' W; 1197m water depth), retrieved during the MD114-IMAGES (International Marine Global Change Study) cruise from the southern part of the Faeroe Bank. This sector was under the proximal influence of European ice sheets (Fennoscandian Ice Sheet to the East, British Irish Ice Sheet to the South) during the last glacial and thus probably responded to the MIS3 pulsed climatic changes. We conducted a multi-proxy analysis of core MD99-2281, including magnetic properties, x-ray fluorescence measurements, characterisation of the coarse (> 150 mu m) lithic fraction (grain concentration) and the analysis of selected biogenic proxies (assemblages and stable isotope ratio of calcareous planktonic foraminifera, dinoflagellate cyst - e.g. dinocyst - assemblages). Results presented here are focussed on the dinocyst response, this proxy providing the reconstruction of past sea-surface hydrological conditions, qualitatively as well as quantitatively (e. g. transfer function sensu lato). Our study documents a very coherent and sensitive oceanic response to the MIS3 rapid climatic variability: strong fluctuations, matching those of stadial/interstadial climatic oscillations as depicted by Greenland ice cores, are recorded in the MD99-2281 archive. Proxies of terrigeneous and detritical material suggest increases in continental advection during Greenland Stadials (including Heinrich events), the latter corresponding also to southward migrations of polar waters. At the opposite, milder sea-surface conditions seem to develop during Greenland Interstadials. After 30 ka, reconstructed pale

The rapid climatic variability characterising the Marine Isotopic Stage (MIS) 3 (similar to 60-30 cal ka BP) provides key issues to understand the atmosphere-ocean-cryosphere dynamics. Here we investigate the response of sea-surface paleoenvironments to the MIS3 climatic variability through the study of a high resolution oceanic sedimentological archive (core MD99-2281, 60 degrees 21' N; 09 degrees 27' W; 1197m water depth), retrieved during the MD114-IMAGES (International Marine Global Change Study) cruise from the southern part of the Faeroe Bank. This sector was under the proximal influence of European ice sheets (Fennoscandian Ice Sheet to the East, British Irish Ice Sheet to the South) during the last glacial and thus probably responded to the MIS3 pulsed climatic changes. We conducted a multi-proxy analysis of core MD99-2281, including magnetic properties, x-ray fluorescence measurements, characterisation of the coarse (> 150 mu m) lithic fraction (grain concentration) and the analysis of selected biogenic proxies (assemblages and stable isotope ratio of calcareous planktonic foraminifera, dinoflagellate cyst - e.g. dinocyst - assemblages). Results presented here are focussed on the dinocyst response, this proxy providing the reconstruction of past sea-surface hydrological conditions, qualitatively as well as quantitatively (e. g. transfer function sensu lato). Our study documents a very coherent and sensitive oceanic response to the MIS3 rapid climatic variability: strong fluctuations, matching those of stadial/interstadial climatic oscillations as depicted by Greenland ice cores, are recorded in the MD99-2281 archive. Proxies of terrigeneous and detritical material suggest increases in continental advection during Greenland Stadials (including Heinrich events), the latter corresponding also to southward migrations of polar waters. At the opposite, milder sea-surface conditions seem to develop during Greenland Interstadials. After 30 ka, reconstructed pale

New dinocyst analyses were conducted on core MD99-2339 retrieved from the central Gulf of Cadiz. Dinocyst and foraminiferal assemblages from this core are combined with existing data off SW Portugal and NW Morocco to investigate past hydrological and primary productivity regimes in the subtropical NE Atlantic Ocean over the last 30 ka. Our results have revealed highest upwelling intensity during Heinrich Stadial 1 (HS 1) and the Younger Dryas and weaker upwelling cells during the Last Glacial Maximum (LGM) and HS 2, off the SW Iberian and NW Moroccan margins. Similar assemblages between the Gulf of Cadiz and the NW Moroccan margin, and distinct species off Portugal, were observed during the cold climatic extremes that punctuated the last 30 ka. This pattern has been linked to the occurrence of a hydrological structure between SW Iberia and Cadiz during the last glacial period, perhaps similar to the modern Azores Front. This front was probably responsible locally for heterotrophic dinocysts found in the Gulf of Cadiz during the last glacial period, even if this sector is not conductive to upwelling phenomena by Ekman transport. Regional reconstructions of paleo-sea-surface temperatures (SSTs) using dinocyst and foraminiferal transfer functions, as well as alkenones, are also discussed and depict coherent scenarios over the last 30 ka. Seasonal reconstructions of LGM SSTs obtained with this multi-proxy panel are discussed jointly with model outputs in order to contribute to ongoing efforts in model-data comparison.

New dinocyst analyses were conducted on core MD99-2339 retrieved from the central Gulf of Cadiz. Dinocyst and foraminiferal assemblages from this core are combined with existing data off SW Portugal and NW Morocco to investigate past hydrological and primary productivity regimes in the subtropical NE Atlantic Ocean over the last 30 ka. Our results have revealed highest upwelling intensity during Heinrich Stadial 1 (HS 1) and the Younger Dryas and weaker upwelling cells during the Last Glacial Maximum (LGM) and HS 2, off the SW Iberian and NW Moroccan margins. Similar assemblages between the Gulf of Cadiz and the NW Moroccan margin, and distinct species off Portugal, were observed during the cold climatic extremes that punctuated the last 30 ka. This pattern has been linked to the occurrence of a hydrological structure between SW Iberia and Cadiz during the last glacial period, perhaps similar to the modern Azores Front. This front was probably responsible locally for heterotrophic dinocysts found in the Gulf of Cadiz during the last glacial period, even if this sector is not conductive to upwelling phenomena by Ekman transport. Regional reconstructions of paleo-sea-surface temperatures (SSTs) using dinocyst and foraminiferal transfer functions, as well as alkenones, are also discussed and depict coherent scenarios over the last 30 ka. Seasonal reconstructions of LGM SSTs obtained with this multi-proxy panel are discussed jointly with model outputs in order to contribute to ongoing efforts in model-data comparison.

Westaway and Bridgland (Earth Surface Processes and Landforms 35: 1071–1094, 2010) discuss the causes, the consequences and the chronology of large-magnitude palaeoflows in Pleistocene river systems of northwest Europe. Based on their calculations, these authors suggest that the combined effects of meltwater from Alpine glaciers, rainfall, snowmelt and melting of permafrost during Heinrich Events (HEs) explain the large-magnitude discharges of the Fleuve Manche palaeoriver which punctuated the last glacial period. This comment identifies some approximations and inconsistencies regarding (i) the timing of the last massive Fleuve Manche palaeoriver discharge and its relation to the de-glacial pattern of the British-Irish Ice Sheet (Point 1); (ii) the palaeoclimatic conditions prevailing on land and the antagonistic forcing mechanism proposed by the authors to explain the large-magnitude palaeoflows (Point 2); (iii) Westaway and Bridgland's (2010) revised interpretation of the deep-sea records from the Bay of Biscay (Point 3); and (iv) the relationship between the offshore sedimentation since the Middle Pleistocene and the formation of the Dover Strait (Point 4). Each point is discussed.

New dinocyst analyses were conducted on core MD99-2339 retrieved from the central Gulf of Cadiz. Dinocyst and foraminiferal assemblages from this core are combined with existing data off SW Portugal and NW Morocco to investigate past hydrological and primary productivity regimes in the subtropical NE Atlantic Ocean over the last 30 ka. Our results have revealed highest upwelling intensity during Heinrich Stadial 1 (HS 1) and the Younger Dryas and weaker upwelling cells during the Last Glacial Maximum (LGM) and HS 2, off the SW Iberian and NW Moroccan margins. Similar assemblages between the Gulf of Cadiz and the NW Moroccan margin, and distinct species off Portugal, were observed during the cold climatic extremes that punctuated the last 30 ka. This pattern has been linked to the occurrence of a hydrological structure between SW Iberia and Cadiz during the last glacial period, perhaps similar to the modern Azores Front. This front was probably responsible locally for heterotrophic dinocysts found in the Gulf of Cadiz during the last glacial period, even if this sector is not conductive to upwelling phenomena by Ekman transport. Regional reconstructions of paleo-sea-surface temperatures (SSTs) using dinocyst and foraminiferal transfer functions, as well as alkenones, are also discussed and depict coherent scenarios over the last 30 ka. Seasonal reconstructions of LGM SSTs obtained with this multi-proxy panel are discussed jointly with model outputs in order to contribute to ongoing efforts in model-data comparison.

Westaway and Bridgland (Earth Surface Processes and Landforms 35: 1071–1094, 2010) discuss the causes, the consequences and the chronology of large-magnitude palaeoflows in Pleistocene river systems of northwest Europe. Based on their calculations, these authors suggest that the combined effects of meltwater from Alpine glaciers, rainfall, snowmelt and melting of permafrost during Heinrich Events (HEs) explain the large-magnitude discharges of the Fleuve Manche palaeoriver which punctuated the last glacial period. This comment identifies some approximations and inconsistencies regarding (i) the timing of the last massive Fleuve Manche palaeoriver discharge and its relation to the de-glacial pattern of the British-Irish Ice Sheet (Point 1); (ii) the palaeoclimatic conditions prevailing on land and the antagonistic forcing mechanism proposed by the authors to explain the large-magnitude palaeoflows (Point 2); (iii) Westaway and Bridgland's (2010) revised interpretation of the deep-sea records from the Bay of Biscay (Point 3); and (iv) the relationship between the offshore sedimentation since the Middle Pleistocene and the formation of the Dover Strait (Point 4). Each point is discussed.

New dinocyst analyses were conducted on core MD99-2339 retrieved from the central Gulf of Cadiz. Dinocyst and foraminiferal assemblages from this core are combined with existing data off SW Portugal and NW Morocco to investigate past hydrological and primary productivity regimes in the subtropical NE Atlantic Ocean over the last 30 ka. Our results have revealed highest upwelling intensity during Heinrich Stadial 1 (HS 1) and the Younger Dryas and weaker upwelling cells during the Last Glacial Maximum (LGM) and HS 2, off the SW Iberian and NW Moroccan margins. Similar assemblages between the Gulf of Cadiz and the NW Moroccan margin, and distinct species off Portugal, were observed during the cold climatic extremes that punctuated the last 30 ka. This pattern has been linked to the occurrence of a hydrological structure between SW Iberia and Cadiz during the last glacial period, perhaps similar to the modern Azores Front. This front was probably responsible locally for heterotrophic dinocysts found in the Gulf of Cadiz during the last glacial period, even if this sector is not conductive to upwelling phenomena by Ekman transport. Regional reconstructions of paleo-sea-surface temperatures (SSTs) using dinocyst and foraminiferal transfer functions, as well as alkenones, are also discussed and depict coherent scenarios over the last 30 ka. Seasonal reconstructions of LGM SSTs obtained with this multi-proxy panel are discussed jointly with model outputs in order to contribute to ongoing efforts in model-data comparison.

Westaway and Bridgland (Earth Surface Processes and Landforms 35: 1071–1094, 2010) discuss the causes, the consequences and the chronology of large-magnitude palaeoflows in Pleistocene river systems of northwest Europe. Based on their calculations, these authors suggest that the combined effects of meltwater from Alpine glaciers, rainfall, snowmelt and melting of permafrost during Heinrich Events (HEs) explain the large-magnitude discharges of the Fleuve Manche palaeoriver which punctuated the last glacial period. This comment identifies some approximations and inconsistencies regarding (i) the timing of the last massive Fleuve Manche palaeoriver discharge and its relation to the de-glacial pattern of the British-Irish Ice Sheet (Point 1); (ii) the palaeoclimatic conditions prevailing on land and the antagonistic forcing mechanism proposed by the authors to explain the large-magnitude palaeoflows (Point 2); (iii) Westaway and Bridgland's (2010) revised interpretation of the deep-sea records from the Bay of Biscay (Point 3); and (iv) the relationship between the offshore sedimentation since the Middle Pleistocene and the formation of the Dover Strait (Point 4). Each point is discussed.

We present a new marine palynological record from the temperate North-eastern Atlantic (core MD03-2692, Celtic-Armorican margin) in the area of influence of the 'Fleuve Manche' paleoriver during glacial times. The runoff of this paleoriver was connected to the glacial history of European ice sheets (including the British Irish Ice Sheet-BIIS). Our study conducted on dinoflagellate cysts assemblages over the last 200 ka, associated with quantification of palynological remains reflecting continental influence (pre-Quaternary dinocysts and micro-algae Pediastrum spp. coenobia), yields detailed insights into the sea-surface paleoenvironments of this sector. More specifically, mechanisms responsible for the origin of unusual deposits of laminated sequences found at the end of Marine Isotope Stage (MIS) 2 and within mid-MIS 6 are here constrained. We provide evidence of genetic similarities between fluvial discharges occurring before and during times of deposition of the laminated deposits. Our study clarifies the causes of the collapse of European glaciated systems. At the end of MIS 2, prior to the deposition of the laminated deposits, plenioceanic influence characterized by high concentrations of Quaternary dinocysts prevailed, and a dinocyst species tracing the penetration of the warm North Atlantic Drift into the Bay of Biscay is recorded. However, this scenario did not recur prior to the deposition of laminated sediments of mid-MIS 6. In addition, contrary to the laminated deposits found at the end of MIS 2 and directly associated with Termination I, MIS 6 laminae appeared 20 ka earlier than Termination II. Our work shows that, during the penultimate glacial stage, the collapse of mid-latitudes ice sheets around 170 ka B.P. may have immediately followed the MIS 6.5 warming phase. Then, the most important melting event around 150 ka B.P. may be linked to a peak in insolation at 65 degrees N, though less important than those during MIS 6.5 and Termination II.

Observation-based reconstructions of sea surface temperature from relatively stable periods in the past, such as the Last Glacial Maximum, represent an important means of constraining climate sensitivity and evaluating model simulations. The first quantitative global reconstruction of sea surface temperatures during the Last Glacial Maximum was developed by the Climate Long-Range Investigation, Mapping and Prediction (CLIMAP) project in the 1970s and 1980s. Since that time, several shortcomings of that earlier effort have become apparent. Here we present an updated synthesis of sea surface temperatures during the Last Glacial Maximum, rigorously defined as the period between 23 and 19 thousand years before present, from the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) project. We integrate microfossil and geochemical reconstructions of surface temperatures and include assessments of the reliability of individual records. Our reconstruction reveals the presence of large longitudinal gradients in sea surface temperature in all of the ocean basins, in contrast to the simulations of the Last Glacial Maximum climate available at present.

We present a new marine palynological record from the temperate North-eastern Atlantic (core MD03-2692, Celtic-Armorican margin) in the area of influence of the 'Fleuve Manche' paleoriver during glacial times. The runoff of this paleoriver was connected to the glacial history of European ice sheets (including the British Irish Ice Sheet-BIIS). Our study conducted on dinoflagellate cysts assemblages over the last 200 ka, associated with quantification of palynological remains reflecting continental influence (pre-Quaternary dinocysts and micro-algae Pediastrum spp. coenobia), yields detailed insights into the sea-surface paleoenvironments of this sector. More specifically, mechanisms responsible for the origin of unusual deposits of laminated sequences found at the end of Marine Isotope Stage (MIS) 2 and within mid-MIS 6 are here constrained. We provide evidence of genetic similarities between fluvial discharges occurring before and during times of deposition of the laminated deposits. Our study clarifies the causes of the collapse of European glaciated systems. At the end of MIS 2, prior to the deposition of the laminated deposits, plenioceanic influence characterized by high concentrations of Quaternary dinocysts prevailed, and a dinocyst species tracing the penetration of the warm North Atlantic Drift into the Bay of Biscay is recorded. However, this scenario did not recur prior to the deposition of laminated sediments of mid-MIS 6. In addition, contrary to the laminated deposits found at the end of MIS 2 and directly associated with Termination I, MIS 6 laminae appeared 20 ka earlier than Termination II. Our work shows that, during the penultimate glacial stage, the collapse of mid-latitudes ice sheets around 170 ka B.P. may have immediately followed the MIS 6.5 warming phase. Then, the most important melting event around 150 ka B.P. may be linked to a peak in insolation at 65 degrees N, though less important than those during MIS 6.5 and Termination II.

The correlation of continental sedimentary records with the marine isotope stratigraphy is a challenge of central importance in Quaternary stratigraphy, particularly in Western Europe where long records of glaciation on land areas are particularly rare. Here we demonstrate for the first time the interrelationship of events during the last 1.2 Ma in an ocean-sediment core from the Bay of Biscay (NE Atlantic), SW of the Channel. The identification of discharge variations from tributary river systems to the 'Fleuve Manche' palaeoriver during glacio-eustatic sea-level lowstands demonstrates the correlation of the marine sediment stratigraphy to the expansion and recession of the European ice-sheets. The amplitude and chronology of European ice-sheet oscillations since the late Early Pleistocene is discussed and our results demonstrate that the first coalescence of the Fennoscandian and British ice-sheets in the North Sea basin ca 450 ka ago caused a profound change in lowstand European drainage alignment. This change caused a rerouting of Fennoscandian and eastern British ice-sheets-derived meltwaters from northwards into the Nordic Seas to southwards into the eastern North Atlantic thereafter. Besides allowing a thorough synchronisation of the European ice-sheet palaeogeography with the well-dated records of palaeoceanographical changes, our results improve the stratigraphy of the English Channel palaeovalleys and will provide important constraints on paleoclimatic scenarios considering the impact that such rerouting and meltwater surges might have on the stability of the oceanic conveyor belt.

Observation-based reconstructions of sea surface temperature from relatively stable periods in the past, such as the Last Glacial Maximum, represent an important means of constraining climate sensitivity and evaluating model simulations1. The first quantitative global reconstruction of sea surface temperatures during the Last Glacial Maximum was developed by the Climate Long-Range Investigation, Mapping and Prediction (CLIMAP) project in the 1970s and 1980s (refs 2, 3). Since that time, several shortcomings of that earlier effort have become apparent4. Here we present an updated synthesis of sea surface temperatures during the Last Glacial Maximum, rigorously defined as the period between 23 and 19 thousand years before present, from the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) project5. We integrate microfossil and geochemical reconstructions of surface temperatures and include assessments of the reliability of individual records. Our reconstruction reveals the presence of large longitudinal gradients in sea surface temperature in all of the ocean basins, in contrast to the simulations of the Last Glacial Maximum climate available at present

Observation-based reconstructions of sea surface temperature from relatively stable periods in the past, such as the Last Glacial Maximum, represent an important means of constraining climate sensitivity and evaluating model simulations. The first quantitative global reconstruction of sea surface temperatures during the Last Glacial Maximum was developed by the Climate Long-Range Investigation, Mapping and Prediction (CLIMAP) project in the 1970s and 1980s. Since that time, several shortcomings of that earlier effort have become apparent. Here we present an updated synthesis of sea surface temperatures during the Last Glacial Maximum, rigorously defined as the period between 23 and 19 thousand years before present, from the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) project. We integrate microfossil and geochemical reconstructions of surface temperatures and include assessments of the reliability of individual records. Our reconstruction reveals the presence of large longitudinal gradients in sea surface temperature in all of the ocean basins, in contrast to the simulations of the Last Glacial Maximum climate available at present.

We present a new marine palynological record from the temperate North-eastern Atlantic (core MD03-2692, Celtic-Armorican margin) in the area of influence of the 'Fleuve Manche' paleoriver during glacial times. The runoff of this paleoriver was connected to the glacial history of European ice sheets (including the British Irish Ice Sheet-BIIS). Our study conducted on dinoflagellate cysts assemblages over the last 200 ka, associated with quantification of palynological remains reflecting continental influence (pre-Quaternary dinocysts and micro-algae Pediastrum spp. coenobia), yields detailed insights into the sea-surface paleoenvironments of this sector. More specifically, mechanisms responsible for the origin of unusual deposits of laminated sequences found at the end of Marine Isotope Stage (MIS) 2 and within mid-MIS 6 are here constrained. We provide evidence of genetic similarities between fluvial discharges occurring before and during times of deposition of the laminated deposits. Our study clarifies the causes of the collapse of European glaciated systems. At the end of MIS 2, prior to the deposition of the laminated deposits, plenioceanic influence characterized by high concentrations of Quaternary dinocysts prevailed, and a dinocyst species tracing the penetration of the warm North Atlantic Drift into the Bay of Biscay is recorded. However, this scenario did not recur prior to the deposition of laminated sediments of mid-MIS 6. In addition, contrary to the laminated deposits found at the end of MIS 2 and directly associated with Termination I, MIS 6 laminae appeared 20 ka earlier than Termination II. Our work shows that, during the penultimate glacial stage, the collapse of mid-latitudes ice sheets around 170 ka B.P. may have immediately followed the MIS 6.5 warming phase. Then, the most important melting event around 150 ka B.P. may be linked to a peak in insolation at 65 degrees N, though less important than those during MIS 6.5 and Termination II.

The correlation of continental sedimentary records with the marine isotope stratigraphy is a challenge of central importance in Quaternary stratigraphy, particularly in Western Europe where long records of glaciation on land areas are particularly rare. Here we demonstrate for the first time the interrelationship of events during the last 1.2 Ma in an ocean-sediment core from the Bay of Biscay (NE Atlantic), SW of the Channel. The identification of discharge variations from tributary river systems to the 'Fleuve Manche' palaeoriver during glacio-eustatic sea-level lowstands demonstrates the correlation of the marine sediment stratigraphy to the expansion and recession of the European ice-sheets. The amplitude and chronology of European ice-sheet oscillations since the late Early Pleistocene is discussed and our results demonstrate that the first coalescence of the Fennoscandian and British ice-sheets in the North Sea basin ca 450 ka ago caused a profound change in lowstand European drainage alignment. This change caused a rerouting of Fennoscandian and eastern British ice-sheets-derived meltwaters from northwards into the Nordic Seas to southwards into the eastern North Atlantic thereafter. Besides allowing a thorough synchronisation of the European ice-sheet palaeogeography with the well-dated records of palaeoceanographical changes, our results improve the stratigraphy of the English Channel palaeovalleys and will provide important constraints on paleoclimatic scenarios considering the impact that such rerouting and meltwater surges might have on the stability of the oceanic conveyor belt.

Observation-based reconstructions of sea surface temperature from relatively stable periods in the past, such as the Last Glacial Maximum, represent an important means of constraining climate sensitivity and evaluating model simulations1. The first quantitative global reconstruction of sea surface temperatures during the Last Glacial Maximum was developed by the Climate Long-Range Investigation, Mapping and Prediction (CLIMAP) project in the 1970s and 1980s (refs 2, 3). Since that time, several shortcomings of that earlier effort have become apparent4. Here we present an updated synthesis of sea surface temperatures during the Last Glacial Maximum, rigorously defined as the period between 23 and 19 thousand years before present, from the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) project5. We integrate microfossil and geochemical reconstructions of surface temperatures and include assessments of the reliability of individual records. Our reconstruction reveals the presence of large longitudinal gradients in sea surface temperature in all of the ocean basins, in contrast to the simulations of the Last Glacial Maximum climate available at present

Observation-based reconstructions of sea surface temperature from relatively stable periods in the past, such as the Last Glacial Maximum, represent an important means of constraining climate sensitivity and evaluating model simulations. The first quantitative global reconstruction of sea surface temperatures during the Last Glacial Maximum was developed by the Climate Long-Range Investigation, Mapping and Prediction (CLIMAP) project in the 1970s and 1980s. Since that time, several shortcomings of that earlier effort have become apparent. Here we present an updated synthesis of sea surface temperatures during the Last Glacial Maximum, rigorously defined as the period between 23 and 19 thousand years before present, from the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) project. We integrate microfossil and geochemical reconstructions of surface temperatures and include assessments of the reliability of individual records. Our reconstruction reveals the presence of large longitudinal gradients in sea surface temperature in all of the ocean basins, in contrast to the simulations of the Last Glacial Maximum climate available at present.

We present a new marine palynological record from the temperate North-eastern Atlantic (core MD03-2692, Celtic-Armorican margin) in the area of influence of the 'Fleuve Manche' paleoriver during glacial times. The runoff of this paleoriver was connected to the glacial history of European ice sheets (including the British Irish Ice Sheet-BIIS). Our study conducted on dinoflagellate cysts assemblages over the last 200 ka, associated with quantification of palynological remains reflecting continental influence (pre-Quaternary dinocysts and micro-algae Pediastrum spp. coenobia), yields detailed insights into the sea-surface paleoenvironments of this sector. More specifically, mechanisms responsible for the origin of unusual deposits of laminated sequences found at the end of Marine Isotope Stage (MIS) 2 and within mid-MIS 6 are here constrained. We provide evidence of genetic similarities between fluvial discharges occurring before and during times of deposition of the laminated deposits. Our study clarifies the causes of the collapse of European glaciated systems. At the end of MIS 2, prior to the deposition of the laminated deposits, plenioceanic influence characterized by high concentrations of Quaternary dinocysts prevailed, and a dinocyst species tracing the penetration of the warm North Atlantic Drift into the Bay of Biscay is recorded. However, this scenario did not recur prior to the deposition of laminated sediments of mid-MIS 6. In addition, contrary to the laminated deposits found at the end of MIS 2 and directly associated with Termination I, MIS 6 laminae appeared 20 ka earlier than Termination II. Our work shows that, during the penultimate glacial stage, the collapse of mid-latitudes ice sheets around 170 ka B.P. may have immediately followed the MIS 6.5 warming phase. Then, the most important melting event around 150 ka B.P. may be linked to a peak in insolation at 65 degrees N, though less important than those during MIS 6.5 and Termination II.

The correlation of continental sedimentary records with the marine isotope stratigraphy is a challenge of central importance in Quaternary stratigraphy, particularly in Western Europe where long records of glaciation on land areas are particularly rare. Here we demonstrate for the first time the interrelationship of events during the last 1.2 Ma in an ocean-sediment core from the Bay of Biscay (NE Atlantic), SW of the Channel. The identification of discharge variations from tributary river systems to the 'Fleuve Manche' palaeoriver during glacio-eustatic sea-level lowstands demonstrates the correlation of the marine sediment stratigraphy to the expansion and recession of the European ice-sheets. The amplitude and chronology of European ice-sheet oscillations since the late Early Pleistocene is discussed and our results demonstrate that the first coalescence of the Fennoscandian and British ice-sheets in the North Sea basin ca 450 ka ago caused a profound change in lowstand European drainage alignment. This change caused a rerouting of Fennoscandian and eastern British ice-sheets-derived meltwaters from northwards into the Nordic Seas to southwards into the eastern North Atlantic thereafter. Besides allowing a thorough synchronisation of the European ice-sheet palaeogeography with the well-dated records of palaeoceanographical changes, our results improve the stratigraphy of the English Channel palaeovalleys and will provide important constraints on paleoclimatic scenarios considering the impact that such rerouting and meltwater surges might have on the stability of the oceanic conveyor belt.