Similarities and dissimilarities between the last two deglaciations and interglaciations in the North Atlantic region

Sea surface temperatures (SSTs) recorded by alkenones and oxygen isotopes in the Alboran basin are used here to describe, at an unprecedented fine temporal resolution, the present interglaciation (PIG, initiated at 11.7kaBP), the last interglaciation (LIG, onset approximately at 129ka) and respective deglaciations. Similarities and dissimilarities in the progression of these periods are reviewed in comparison with ice cores and stalagmites. Cold spells coeval with the Heinrich events (H) described in the North Atlantic include multi-decadal scale oscillations not previously obvious (up to 4°C in less than eight centuries within the stadials associated with H1 and H11, ca133ka and 17ka respectively). These abrupt oscillations precede the accumulation of organic rich layers deposited when perihelion moves from alignment with NH spring equinox to the summer solstice, a reference for deglaciations. Events observed during the last deglaciation at 17ka, 14.8ka and 11.7ka are reminiscent of events occurred during the penultimate deglaciation at ca136ka, 132ka and 129ka, respectively. The SST trend during the PIG is no more than 2°C (from 20°C to 18°C; up to-0.2°C/ka). The trend is steeper during the LIG, i.e. up to a 5°C change from the early interglaciation to immediately before the glacial inception (from 23°C to 18°C; up to-0.4°C/ka). Events are superimposed upon a long term trend towards colder SSTs, beginning with SST maxima followed by temperate periods until perihelion aligned with the NH autumn equinox (before ca5.3ka for the PIG and 121ka for the LIG). A cold spell of around eight centuries at 2.8ka during the PIG was possibly mimicked during the LIG at ca118ka by a SST fall of around 1°C in a millennium. These events led interglacial SST to stabilise at around 18°C. The glacial inception, barely evident at the beginning ca115ka (North Atlantic event C25, after perihelion passage in the NH winter solstice), culminated with a SST drop of at least 2°C in two millennia (event C24, ca111ka). The Little Ice Age (0.7ka) also occurred after the latest perihelion passage in the NH winter solstice and could be an example of how a glacial pre-inception event following an interglaciation might be.a Department of Environmental Chemistry, Institute of Environmental Assessment and Water Research (IDÆA), Spanish Council for Scientific Research (CSIC), 08034 Barcelona, Spain b University of Cambridge, Department of Earth Sciences, Downing Street, Cambridge CB2 3EQ, United Kingdom c Institute of Environmental Science and Technology and Department of Geography, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain d Institució Catalana de Recerca i Estudis Avançats (ICREA), Inst. of Environmental Science and Technology and Dept. of Geography, Universitat Autònoma de Barcelona, 08193 Bellaterra, SpainPeer reviewe