Mean global ocean temperatures during the last glacial transition

Abstract

Little is known about the ocean temperature's long-term response to climate perturbations owing to limited observations and a lack of robust reconstructions. Although most of the anthropogenic heat added to the climate system has been taken up by the ocean up until now, its role in a century and beyond is uncertain. Here, using noble gases trapped in ice cores, we show that the mean global ocean temperature increased by 2.57 ± 0.24 degrees Celsius over the last glacial transition (20,000 to 10,000 years ago). Our reconstruction provides unprecedented precision and temporal resolution for the integrated global ocean, in contrast to the depth-, region-, organism- and season-specific estimates provided by other methods. We find that the mean global ocean temperature is closely correlated with Antarctic temperature and has no lead or lag with atmospheric CO, thereby confirming the important role of Southern Hemisphere climate in global climate trends. We also reveal an enigmatic 700-year warming during the early Younger Dryas period (about 12,000 years ago) that surpasses estimates of modern ocean heat uptake.

Response of a comprehensive climate model to a broad range of external forcings: relevance for deep ocean ventilation and the development of late Cenozoic ice ages

“…The simulated salinity at Shona Rise is only 36.4, rather than the reconstructed 37.1 ± 0.2, but the robustness of the Shona Rise reconstruction has been questioned (Wunsch 2016) so we are unsure whether or not this discrepancy is significant. The model also simulates a change in Mean Ocean Temperature of 2.47 °C between the pre-industrial control and the 'glacial' state, which is indistinguishable from the recent estimate of 2.57 ± 0.24 ºC derived from noble gas ratios in Antarctic ice (Bereiter et al 2018). Thus, we are unable to identify a significant bias in the model simulation of the glacial-interglacial change in deep ocean temperature and salinity.…”

Is the Noble Gas‐Based Rate of Ocean Warming During the Younger Dryas Overestimated?

“…Gray bar highlights CH 4 data used to estimate smoothing at TG. (b) Splined MOT records for TG (orange) and WD (blue; Bereiter, Shackleton, et al, ). Crosses indicate location of MOT data used to produce spline.…”

Evaluating the link between the sulfur-rich Laacher See volcanic eruption and the Younger Dryas climate anomaly

“…The best age estimate of the LSE is shown (red circle) (Brauer et al, 2008;Lane et al, 2015), and a possible correlation to a synchronous sulfate spike highlighted by the vertical dashed arrow. The large spike at ∼ 13 ka BP represents a smaller but more proximal Icelandic eruption (Hekla) associated with a volcanic ash layer (Mortensen et al, 2005;Bereiter et al, 2018). abrupt cooling predates this by ∼ 24 years) (Fig.…”

“…Research now indicates that the YD was indeed characterised by cold conditions across the North Atlantic and Europe (Carlson et al, 2007;von Grafenstein et al, 1999) but also by a southwardshifted westerly wind belt over Europe (Bakke et al, 2009;Brauer et al, 2008;Lane et al, 2013a;Baldini et al, 2015b), a southward-shifted Intertropical Convergence Zone (Shakun et al, 2007;Chiang and Bitz, 2005;Bahr et al, 2018), increased moisture across the southwest of North America (Polyak et al, 2004;Asmerom et al, 2010), and potential warming in parts of the Southern Hemisphere (Bereiter et al, 2018;Kaplan et al, 2010).…”