The mechanism which leads to glacial and interglacial events with a period of about 100,000 years is poorly understood. A promising area of research in understanding the mechanism behind the alternating glacial/deglacial which is pursued in this article is the relationship between the temperatures of the North Pacific and North Atlantic basins and its impact on global climate.

Data


In this study ocean sediments have been analyzed in the Gulf of Alaska (GOA) over the past 18,000 years. The resolution is about 80 years during the current deglacial period (present to 11,000 years ago), about 10 years in the deglacial interval (11,000 to 14,600 years ago), and about 35 years during the late glacial period (14,700 to 18,000 years ago). Sediments were dated by radiocarbon dating and a known volcanic event which left debris in the sediment record. The GOA sediment record tracks local temperature, salinity, and global ice volume. Other data collected in the North Pacific indicate that the sediment record there reflects upper-ocean temperature.

In the North Atlantic, the North Greenland Ice Core Project (NGRIP) has analyzed ice cores for the same period. NGRIP ice cores record local temperature, moisture transport, and global ice volume. The NGRIP temperature record correlates with the marine paleotemperature records from the subpolar North Atlantic.

Analysis


By comparing the temperature records in the North Pacific and the North Atlantic, see the graphs below, it can be seen that over most of the past 18,000 years, the relationship between sea temperatures in the North Atlantic and North Pacific was often a seasaw. About 15,500 years ago, starting several hundred years before the abrupt Bølling warming 14,600 years ago, the North Atlantic and North Pacific climate records become synchronized, meaning similar temperature in the two basins. After the Bølling warming period (14,700 to 14,100 years ago), the North Atlantic and North Pacific climate records again become highly synchronized just before the abrupt warming which initiated the present deglacial period (the Holocene). The North Atlantic and North Pacific climate records become anti-synchronized at about 10,000 years ago, suggesting a return to a Pacific-Atlantic seesaw.

This provides further evidence that to understand Earth's glacial/deglacial cycles requires a combination of external inputs such as solar radiation and the internal dynamics of Earth's climate system including its atmosphere, oceans and ice sheets.

Correlation between North Atlantic and North Pacific sea surface temperatures
Correlation between North Atlantic and North Pacific sea surface temperatures

Figure Comparison of North Pacific and North Atlantic climate variability. (A) The North Pacific temperature proxy (GOA δ18O) record (rose line) plotted with the North Atlantic temperature proxy (NGRIP δ18O) record (dark blue). (B) Cross correlation between the North Pacific and North Atlantic temperature records. The black line and gray lines reflect two different ways of determining the ages of the North Pacific sediments. The pink shading identifies the period where there is significant correlation between the North Pacific and North Atlantic climate records. The gray shading identifies periods with either no significant correlation or a seesaw-like mode between records.

Praetorius and Mix, Science 25 July 2014: Vol. 345 no. 6195 pp. 444-448 DOI: 10.1126/science.1252000