How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic


Evidence for the Little Ice Age Way "Down Under"
Reference
Domack, E., Leventer, A., Dunbar, R., Taylor, F., Brachfeld, S., Sjunneskog, C. and ODP Leg 178 Scientific Party. 2001. Chronology of the Palmer Deep site, Antarctic Peninsula: A Holocene palaeoenvironmental reference for the circum-Antarctic. The Holocene 11: 1-9.

What was done
Ocean sediment cores were obtained from a prominent depression - the Palmer Deep - located on the inner continental shelf of the western Antarctic Peninsula (64 51.71' S, 64 12.47' W) and subjected to radiocarbon and spectral analyses to provide a high resolution proxy temperature history spanning the past 13,000 years.

What was learned
According to the authors, the proxy records displayed five prominent palaeoenvironmental intervals over the past 14,000 years: (1) a "Neoglacial" cool period beginning 3360 years ago and continuing to the present, (2) a mid-Holocene climatic optimum from 9070 to 3360 years ago, (3) a cool period beginning 11,460 years ago and ending at 9070 years ago, (4) a warm period from 13,180 to 11,460 years ago, and (5) cold glacial conditions prior to 13,180 years ago. Spectral analyses of the data revealed that, superimposed upon these broad climatic intervals, were decadal and centennial-scale temperature cycles. Throughout the current Neoglacial period, the authors report finding "very significant" (above the 99% confidence level) peaks, or oscillations, that occurred at intervals of 400, 190, 122, 85 and 70 years, which they suggest are perhaps driven by solar variability. Additionally, the authors note the presence of a "Little Ice Age" that started about 700 years before present and ended approximately 100 years ago.

What it means
The results of this study add to the mounting body of evidence that supports a global Little Ice Age event. It also highlights the inherent natural variability of climate, and suggests to us the high probability that recent 20th century warming is not of anthropogenic origin, but the result of natural variability, as the earth has recovered from the now-demonstrated global chill of the Little Ice Age.