Estimates of sea surface temperatures in the Coral Sea

The CLIMAP [1981] reconstruction of the Coral Sea found relatively little cooling (2°C) in the low latitudes (10°S) but a warming off Australia at about 25°S. The small low-latitude changes are of interest because terrestrial pollen and snowline data from the New Guinea highlands imply that surface temperatures may have been 6° to 9°C colder at the last glacial maximum (LGM). The purpose of this paper is to evaluate these conclusions on the basis of additional core sites, new oxygen isotope stratigraphy, and new sea surface temperature (SST) estimates using the modern analog technique (MAT). In the northern Coral Sea, planktonic foraminifer assemblages consist of tropical-subtropical species that show little change over the past 20 kyr. Quantitative estimates of SST using the modern analog technique (MAT) confirm the CLIMAP [1981] conclusion that little or no temperature change occurred in this tropical region at the LGM, thus reinforcing the conflict with terrestrial evidence. In the southern region (25°S), two cores indicate that foraminifer faunas became more subtropical at the LGM. The MAT estimates for the LGM are 3° to 4°C colder than modern, producing a steeper thermal gradient in the southern Coral Sea. These data remove the warm SST anomaly along the eastern coast of Australia and indicate that during the LGM, cool high- latitude waters were displaced northward along the coast of Australia into the southern Coral Sea.

1981年CLIMAP开展的珊瑚海古气候重建结果显示，低纬度区域（南纬10°）的降温幅度相对较小（2℃），但在南纬25°附近的澳大利亚外海存在升温现象。该区域低纬度的微小温度变化引发学界关注，因为来自新几内亚高地的陆地花粉与雪线数据表明，末次冰盛期（Last Glacial Maximum, LGM）的地表温度可能较现代偏低6℃至9℃。本文旨在基于新增岩芯位点、新的氧同位素地层学数据，以及采用现代类比法（Modern Analog Technique, MAT）得到的新海面温度（Sea Surface Temperature, SST）估算结果，对上述结论展开评估。在珊瑚海北部，浮游有孔虫（planktonic foraminifer）组合以热带-亚热带物种为主，且在过去2万年中几乎未发生显著变化。采用现代类比法（MAT）得到的SST定量估算结果证实了CLIMAP[1981]的结论，即该热带区域在末次冰盛期几乎未出现温度变化，这进一步加剧了与陆地古气候证据之间的矛盾。在南纬25°的南部区域，两处岩芯数据显示，末次冰盛期的有孔虫动物群向亚热带类群偏移。基于MAT得到的末次冰盛期SST估算结果较现代低3℃至4℃，使得珊瑚海南部的温度梯度更为陡峭。上述数据推翻了澳大利亚东海岸存在SST暖异常的推论，并表明在末次冰盛期，寒冷的高纬度海水沿澳大利亚海岸向北推移，侵入了珊瑚海南部海域。