In Northern Hemisphere deglaciation records, the transition from the last glacial to the Holocene indicates a rapid return to near-glacial conditions during the Younger Dryas, whereas their Southern Hemisphere ice core counterparts record two separate cooling events: the Antarctic Cold Reversal and the Oceanic Cold Reversal. Spatial distribution and relative timing of these events in both hemispheres are central for our understanding of causes and mechanisms of abrupt climate change. To date, no marine record from the southern mid-latitudes conclusively demonstrates that the Younger Dryas was a significant event in the Southern Ocean. Here, we present high-resolution oxygen isotope and iron content records of a radiocarbon-dated sedimentary sequence from the Great Australian Bight, which constrains oceanic and atmospheric changes during the last deglaciation. Oxygen isotopes from planktonic foraminifera indicate two rapid cold reversals (between 13.1 and 11.1 kyr BP) separated by a brief warming. The sedimentary iron content, interpreted as a proxy for wind strength, indicates a simultaneous change in atmospheric circulation pattern. Both records demonstrate the existence of cooling events in the Southern Hemisphere, which are synchronous with the Northern Hemisphere Younger Dryas cold reversal (between 12.9 and 11.5 kyr BP). Such evidence for the spatial distribution and timing of abrupt climatic fluctuations is essential data for groundtruthing results derived from global climate models.

All dates are based on monospecific samples of the planktonic foraminifer Globorotalia inflata measured at the Swiss Federal Institute of Technology AMS facility (Bonani et al., 1987, doi:10.1016/0168-583X(87)90210-2). 14C ages were converted into calendar ages using the Calib 4.3 program (http://radiocarbon.pa.qub.ac.uk/calib) and the marine calibration dataset MARINE 98 (Stuiver and Braziunas, 1993; Stuiver et al., 1998), which includes the 400-year correction for the ocean surface reservoir effect (Bard et al., 1984 doi:10.1016/0012-821X(94)90112-0). The local effect, the difference DeltaR (Stuiver and Braziunas, 1993) in reservoir age of the local region and the model ocean, is, on average, 61 +/- 29 years for the GAB region (Reimer and Reimer, 2001 http://www.calib.org).

Supplement to: Andres, Miriam S; Bernasconi, Stefano M; McKenzie, Judith A; Röhl, Ursula (2003): Southern Ocean deglacial record supports global Younger Dryas. Earth and Planetary Science Letters, 216(4), 515-524