Glacial geomorphology, fluvial geomorphology, hillslope geomorphology, submarine geomorphology, tectonic geomorphology...

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Tuesday, 28 September 2010

NZ-YD#2: Maybe the Waiho Loop is a climate signal

Kaplan et al., (2010), Figure 2. Central Southern Alps about 13 000 yr ago
Michael Kaplan is back in the New Zealand Younger Dryas debate this week, as coauthor with Aaron Putnam et al. in Nature Geoscience. This investigation of the Birch Hill moraine, again using 10Be cosmogenic dates, shows that the Antarctic Cold Reversal (ACR) did cause glacial advance in the Pukaki catchment at 12.97 ka and a similar expansion of the nearby Macaulay glacier, so the ACR is likely to have been a Southern Hemisphere-wide cooling event. This provides further weight to the bipolar seesaw hypothesis; simply that one hemisphere cools whilst the other warms. These results also correspond to a climatic driver for the Franz Josef glacier advancing to form the Waiho Loop moraine, rather than the landslide origin proposed by Tovar et al., (2008) amongst others, as evidence against a Younger Dryas in New Zealand. A climate origin for this moraine would indicate ACR cooling in New Zealand that occurred asynchronously to the Northern Hemisphere YD. So was New Zealand warm or cold between 13-11 ka? An ongoing discussion...