Late Pleistocene to Holocene composite speleothem 18O and 13C chronologies from South Island, New Zealand—did a global Younger Dryas really exist?

Details Late Pleistocene to Holocene composite speleothem 18O and 13C chronologies from South Island, New Zealand—did a global Younger Dryas really exist? Late Pleistocene to Holocene composite speleothem 18O and 13C chronologies from South Island, New Zealand—did a global Younger Dryas really exist?

Feb 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005e%26psl.230..301w&link_type=abstract

Earth and Planetary Science Letters, Volume 230, Issue 3-4, p. 301-317.

Mathematics

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19

Scientific paper

Oxygen and carbon data from eight stalagmites from northwest South Island are combined to produce composite records of δ18O and δ13C from 23.4 ka to the present. The chronology is anchored by 43 thermal ionization mass spectrometry (TIMS) uranium series ages. Delta 18O values are interpreted as having a first order positive relationship to temperature, but also to be influenced by precipitation in a complex manner. Delta 13C is interpreted as responding negatively to increases in atmospheric CO2 concentration, biological activity and precipitation amount. Six climatic phases are recognized. After adjustment of 1.2‰ for the ice volume effect, the δ18O record between 23 and 18 ka varies around -3.72‰ compared to the Holocene average of -3.17‰. Late-glacial warming commenced between 18.2 and 17.8 ka and accelerated after 16.7 ka, culminating in a positive excursion between 14.70 and 13.53 ka. This was followed by a significant negative excursion between 13.53 and 11.14 ka of up to 0.55‰ depth that overlapped the Antarctic Cold Reversal (ACR) and spanned the Younger Dryas (YD). Positive δ18O excursions at 11.14 ka and 6.91 6.47 ka represent the warmest parts of the Holocene. The mid-Holocene from 6 to 2 ka was marked by negative excursions that coincide with increased glacial activity in the South Island. A short positive excursion from 0.71 to 0.57 ka was slightly later than the Medieval Warm Period of Europe. Delta 13C values were high until 17.79 ka after which there was an abrupt decrease to 17.19 ka followed by a steady decline to a minimum at 10.97 ka. Then followed a general increase, suggesting a drying trend, to 3.23 ka followed by a further general decline. The abrupt decrease in δ-values after 17.79 ka probably corresponds to an increase in atmospheric CO2 concentration, biological activity and wetness at the end of the Last Glaciation, but the reversal identified in the δ18O record from 13.53 to 11.14 ka was not reflected in δ13C changes. The lowest δ13C values coincided with the early Holocene climatic suboptimum when conditions were relatively wet as well as mild. Major trends in the δ18Oc record are similar to the Northern Hemisphere, but second order detail is often distinctly different. Consequently, at the millennial scale, a more convincing case can be made for asymmetric climatic response between the two hemispheres rather than synchronicity.

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