Thursday, September 15, 2011

New paper finds SE Pacific Ocean was 2C warmer 10,000 years ago with 'safe' CO2 levels

A paper published today in the journal Paleoceanography finds that sea surface temperatures of the southeastern Pacific Ocean were 2C higher than the present 10,000 years ago near the beginning of the current interglacial period.

Top two graphs show proxies of SE Pacific Ocean sea surface temperatures over the past 70,000 years. Horizontal axis shows thousands of years before the present. The last major ice age extends from about 60,000 to 18,000 years ago. The current interglacial period was significantly warmer 10,000 years before the present.

PALEOCEANOGRAPHY, VOL. 26, PA3221, 10 PP., 2011
Key Points
  • Glacial millennial-scale paleoceanographic changes in the southeast Pacific
  • Antarctic timing and structure of SSTs and d18O very similar to ODP site 1233
  • Northward shift of Southern Ocean fronts and the opal belt during cold periods
M. Caniupán et al
Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany

Glacial millennial-scale paleoceanographic changes in the Southeast Pacific and the adjacent Southern Ocean are poorly known due to the scarcity of well-dated and high resolution sediment records. Here we present new surface water records from sediment core MD07-3128 recovered at 53°S off the Pacific entrance of the Strait of Magellan. The alkenone-derived sea surface temperature (SST) record reveals a very strong warming of ca. 8°C over the last Termination and substantial millennial-scale variability in the glacial section largely consistent with our planktonic foraminifera oxygen isotope (δ18O) record of Neogloboquadrina pachyderma (sin.). The timing and structure of the Termination and some of the millennial-scale SST fluctuations are very similar to those observed in the well-dated SST record from ODP Site 1233 (41°S) and the temperature record from Drowning Maud Land Antarctic ice core supporting the hemispheric-wide Antarctic timing of SST changes. However, differences in our new SST record are also found including a long-term warming trend over Marine Isotope Stage (MIS) 3 followed by a cooling toward the Last Glacial Maximum (LGM). We suggest that these differences reflect regional cooling related to the proximal location of the southern Patagonian Ice Sheet and related meltwater supply at least during the LGM consistent with the fact that no longer SST cooling trend is observed in ODP Site 1233 or any SST Chilean record. This proximal ice sheet location is documented by generally higher contents of ice rafted debris (IRD) and tetra-unsaturated alkenones, and a slight trend toward lighter planktonic δ18O during late MIS 3 and MIS 2.

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