Rapid Reductions in North Atlantic Deep Water During the Peak of the Last Interglacial Period

Abstract

Deep ocean circulation has been considered relatively stable during interglacial periods, yet little is known about its behavior on submillennial time scales. Using a subcentennially resolved epibenthic foraminiferal δ(13)C record, we show that the influence of North Atlantic Deep Water (NADW) was strong at the onset of the last interglacial period and was then interrupted by several prominent centennial-scale reductions. These NADW transients occurred during periods of increased ice rafting and southward expansions of polar water influence, suggesting that a buoyancy threshold for convective instability was triggered by freshwater and circum-Arctic cryosphere changes. The deep Atlantic chemical changes were similar in magnitude to those associated with glaciations, implying that the canonical view of a relatively stable interglacial circulation may not hold for conditions warmer and fresher than at present.

Last interglacial temperature seasonality reconstructed from tropical Atlantic corals

“…These modelling efforts reveal that the mid-LIG increased SST seasonality in the Caribbean Sea results primarily from summer warming, contrary to the conclusion reached in Winter et al (2003). Our coral Sr/Ca records and time-slice simulations also further substantiate the transient modelling and hosing experiments (Felis et al, 2015) that demonstrate the insensitivity of tropical SST seasonality to the wider climate instabilities that perturbed the Atlantic realm during the LIG (Sirocko et al, 2005;Blanchon et al, 2009;O'Leary et al, 2013;Galaasen et al, 2014;Mokeddem et al, 2014). In summary, our results affirm the prevailing influence of orbital insolation changes on tropical SST seasonality.…”

“…The LIG was punctuated by profound changes and instabilities. However, as demonstrated by a water hosing experiment performed on model simulations of LIG climate and a coral proxy record (Felis et al, 2015), temperature seasonality in the tropical Atlantic was relatively insensitive to the influences of monumental ice sheet loss (Blanchon et al, 2009), sea level rise (O'Leary et al, 2013), rapid reorganisation of oceanic currents (Galaasen et al, 2014), cold events (Mokeddem et al, 2014) and abrupt climatic shifts (Sirocko et al, 2005).…”

Stable isotope compositions of speleothems from the last interglacial – Spatial patterns of climate fluctuations in Europe

“…As also shown in Fig. 10, stable isotope peaks obtained for planctonic foraminifers at 125-124 ka appear in several North Atlantic deep sea cores around Greenland , Van Nieuwenhove et al, 2011Irvalı et al, 2012;Galaasen et al, 2014), and may be interpreted as a result of a Younger Dryas type event (Bauch, 2013). The event is generally explained as resulting from a freshwater influx from melting ice sheets that induced a reduction in the Atlantic Meridional Overturning Circulation (AMOC) and associated cooling in the northernmost parts of the Atlantic realm.…”

“…10) such as the Greenland ice core δ 18 O data (North Greenland Ice Core Project members, 2004; using the GICC05 age scale of Wolff et al, 2010) and selected stable isotope compositions and sea surface temperature reconstructions derived from North Atlantic deep sea sediment cores Sánchez-Goñi et al, 2012;Galaasen et al, 2014). It should be noted here that dating of deep sea records is a challenging task (e.g., Drysdale et al, 2009), and the North Atlantic region may behave heterogeneously with respect to temperature anomalies during climate change events (Capron et al, 2014) that must be kept in mind during the evaluation.…”

Deep Atlantic variability during the last interglacial period

“…yes, suggests our ultra-highly resolved stable isotope record generated as part of the Past4Future project. Galaasen et al (2014) reconstructed variability in NADW over the LIG using epibenthic foraminifera C. wuellerstorfi δ 13 C from the Eirik Drift (Fig. 1).…”