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The causes and consequences of the episodic iceberg-discharge events from the Hudson Strait Ice Stream of the Laurentide Ice Sheet, or Heinrich events (HE), are one of the most explored topics in Pleistocene palaeoclimatology. In this chapter, we summarise three decades of intense research while introducing recent results from both the European and Cordilleran Ice Sheets that could call for a paradigm shift in our understanding of the HE.

This chapter describes the millennial-scale climatic variability in the atmosphere of Greenland during the Last Glacial Cycle (MIS 5e–MIS 1, 116–14.7 cal ka BP), that is, the Dansgaard–Oeschger (D–O) cycles, and the associated global changes in greenhouse gas atmospheric concentrations, particularly CO2 and CH4, and atmospheric circulation (Ca2+ concentration and d-excess). This chapter highlights the contrasting regional impact of the D–O cycles on the North Atlantic Sea surface temperatures and the vegetation and climate across Europe, as well as the synchronicity between changes in Greenland temperature and the hydrological cycle in the tropics and midlatitudes of the Northern Hemisphere. By contrast, the shape and phasing of millennial-scale events between Greenland and Antarctica differ between the two regions. The mechanisms underlying such a variability are still under debate.

This chapter summarises the environmental changes that accompanied the rapid growth of the Northern Hemisphere ice sheets c. 35–30 cal ka BP and their maximum extent c. 29–19 cal ka BP, with a special focus on the European continent and its surrounding margins.

The increasingly popular opinion that temperate plant and animal species persisted in many small refugia in Europe north of the main southern peninsular refugia directly challenges a classical paradigm. As indirect evidence for the existence of such glacial microrefugia readily accumulates, it is interesting to note that the few direct in situ occurrences of fossils testifying their local existence are almost always debated. Our recent study on European beech (Fagus sylvatica) refugia in south-western France was no exception to this trend. Yet, as mentioned by the philosopher Bertrand Russell, it is not possible ‘to get anywhere if we start from skepticism. We must start from a broad acceptance of whatever seems to be knowledge and is not rejected for some specific reason.’ We therefore believe that no a priori preference should be given to one of the two scenarios of migration from a distant macro-refugium or of survival in situ in small refugia. Microrefugia are by definition spatially restricted and include few and possibly less fit individuals, so that a direct assessment for their existence at the stand-scale is extremely challenging. In fact, without prior information on the possible location of these refugia, finding fossils testifying to their existence is akin to looking for a needle in a haystack. We believe that to uncover glacial micro-refugia, the fossil record needs not to be abundant, as long as the claims are reasonable and the dataset includes both indirect and robust direct field evidence for local presence during the most severe climatic conditions. The criticisms of Huntley extend beyond our own study to other recently published studies on so-called cryptic glacial refugia, that is putative microrefugia inferred indirectly from genetic analyses of extant populations, species distribution modeling (SDM) or regional-scale pollen analyses. As we will now show, considerable progress has been made recently in these fields that deserve to be more widel

The relationships between climate, vegetation and fires are a major subject of investigation in the context of climate change. In southern Africa, fire is known to play a crucial role in the existence of grasslands and Mediterranean-type biomes. Microcharcoal-based reconstructions of past fire activity in that region have shown a tight correlation between grass-fueled fires and the precessional cycle, with maximum fire activity during maxima of the climatic precession index. These changes have been interpreted as the result of changes in fuel load in response to precipitation changes in eastern southern Africa. Here we use the general circulation model IPSL_CM5A (Institut Pierre Simon Laplace Climate Model version 5A) and the dynamic vegetation model LPJ-LMfire to investigate the response of climate, vegetation and fire activity to precession changes in southern Africa during marine isotopic stage 4 (74-59 kyr BP). We perform two climatic simulations, for a maximum and minimum of the precession index, and use a statistical downscaling method to increase the spatial resolution of the IPSL_CM5A outputs over southern Africa and perform high-resolution simulations of the vegetation and fire activity. Our results show an anticorrelation between the northern and southern African monsoons in response to precession changes. A decrease of the precession climatic index leads to a precipitation decrease in the summer rainfall area of southern Africa. The drying of climate leads to a decrease of vegetation cover and fire activity. Our results are in qualitative agreement with data and confirm that fire activity in southern Africa during MIS4 is mainly driven by vegetation cover.

Sediments cored along the southwestern Iberian margin during Integrated Ocean Drilling Program Expedition 339 provide constraints on Mediterranean Outflow Water (MOW) circulation patterns from the Pliocene epoch to the present day. After the Strait of Gibraltar opened (5.33 million years ago), a limited volume of MOW entered the Atlantic. Depositional hiatuses indicate erosion by bottom currents related to higher volumes of MOW circulating into the North Atlantic, beginning in the late Pliocene. The hiatuses coincide with regional tectonic events and changes in global thermohaline circulation (THC). This suggests that MOW influenced Atlantic Meridional Overturning Circulation (AMOC), THC, and climatic shifts by contributing a component of warm, saline water to northern latitudes while in turn being influenced by plate tectonics.

Three highly resolved pollen and sea surface temperature records from the Iberian margin (36-42 degrees N) reveal the local evolution of vegetation and climate associated with the rapid climatic variability of marine isotope stage 3. The comparison of the climate at these midlatitudes with delta D and d excess from Greenland ice cores shows that the north-south climatic gradient underwent strong variations during the long Greenland Interstadials (GIs) 8 and 12. After the Northern Hemispheric rapid warming at the Greenland Stadial (GS)-GI transition, the trend during the first part of the GI is a Greenland cooling and an Iberian warming. This increase of the North Atlantic climatic gradient led to moisture transportation to Greenland from midlatitudes (lightest d excess) and to a drying episode in Iberia. The subsequent temperature decrease in Greenland and Iberia associated with the precipitation increase in the latter region occurred when the major source of Greenland precipitation shifted to lower latitudes (d excess increase).

© 2009 The Authors. This article is distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Climate of the Past 5 (2009): 53-72, doi:10.5194/cp-5-53-2009, We present a new high-resolution marine pollen record from NW Iberian margin sediments (core MD03-2697) covering the interval between 340 000 and 270 000 years ago, a time period centred on Marine Isotope Stage (MIS) 9 and characterized by particular baseline climate states. This study enables the documentation of vegetation changes in the north-western Iberian Peninsula and therefore the terrestrial climatic variability at orbital and in particular at millennial scales during MIS 9, directly on a marine stratigraphy. Suborbital vegetation changes in NW Iberia in response to cool/cold events are detected throughout the studied interval even during MIS 9e ice volume minimum. However, they appear more frequent and of higher amplitude during the 30 000 years following the MIS 9e interglacial period and during the MIS 9a-8 transition, which correspond to intervals of an intermediate to high ice volume and mainly periods of ice growth. Each suborbital cold event detected in NW Iberia has a counterpart in the Southern Iberian margin SST record. High to moderate amplitude cold episodes detected on land and in the ocean appear to be related to changes in deep water circulation and probably to iceberg discharges at least during MIS 9d, the mid-MIS 9c cold event and MIS 9b. This work provides therefore additional evidence of pervasive millennial-scale climatic variability in the North Atlantic borderlands throughout past climatic cycles of the Late Pleistocene, regardless of glacial state. However, ice volume might have an indirect influence on the amplitude of the millennial climatic changes in Southern Europe., This research was supported by IPEV (Institut Paul Emile Victor), PNEDC (Programme National d’Etude de la Dynamique du Climat), the Gary Comer Science and Education Foundation and the US National Science Foundation (OCE grants 8-4911100 and 8-256500).