North Atlantic Versus Global Control on Dansgaard‐Oeschger Events. Issue 23 (2nd December 2018)

• Record Type: Journal Article
• Authors: Dima, M.; Lohmann, G.; Knorr, G.
• Is Part Of: Geophysical research letters. Volume 45:Issue 23(2018)
• Page Start: 12, 991
• Page End: 12, 998
• Publication Date: 2018-12-02
• Subjects: Dansgaard‐Oeschger events -- thermohaline circulation -- hysteresis diagram -- global forcing -- Southern Hemisphere; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2018GL080035
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: The classic scenario for the generation of Dansgaard‐Oeschger (DO) events assumes a link to changes in the Atlantic Meridional Overturning Circulation (AMOC) induced by North Atlantic freshwater perturbations. Recent proxy data emphasize the existence of leads and lags between DO fingerprints in Greenland and Antarctic records, highlighting the potential of a Southern Hemisphere control on these events. Investigating this possibility, we provide a conceptual model resulting from phase space reconstructions based on the northern and southern ice core records. The resulting patterns closely resemble AMOC hysteresis, consistent with a northern abrupt warming linked to gradual global temperature changes. This suggests that rapid DO warmings associated with abrupt AMOC transitions from a relatively weak (cold stadial) state to a stronger (warm interstadial) state can be controlled by global forcing that can be linked to the Southern Hemisphere, rather than by the end of a local temporary forcing in the North Atlantic. Plain Language Summary: The most spectacular abrupt climate changes over the last 120, 000 years, known as Dansgaard‐Oeschger events, manifest as up to 10 °C warmings developed in just a few decades in the North Atlantic sector, with a clear corresponding footprint on Antarctica. Although it is generally assumed that the main causes of these warmings are linked to changes in the Atlantic Ocean circulation, their triggers are not yet identified. Simulations performed with general circulation models indicate that rapid intensifications of the Atlantic Ocean circulation could be induced by a global temperature forcing linked to the Southern Hemisphere and that their mutual dependence has a specific hysteresis pattern. Here we use temperature paleo‐records from Greenland and Antarctica, associated to each DO event, to show that their mutual dependence pattern closely resembles the hysteresis derived through general circulation models. The resemblance suggests that the DO warming events are induced by a global forcing linked to the Southern Hemisphere. Key Points: Antarctica and Greenland paleo‐temperature records associated to DO events are used to construct phase space representations The phase space representations' patterns closely resemble the AMOC hysteresis behavior emphasized in numerical simulations The resemblance between reconstructed and simulated hysteresis points to a global forcing for DO warmings, linked to the Southern Hemisphere