Tuesday, May 27, 2014

New paper finds Antarctic temperatures were warmer in 1800's and 1940's

A new paper published in the Annals of Glaciology shows Antarctic air temperatures were warmer during the early 1800's and 1940's in comparison to the end of the 20th century. The authors find evidence of a quasi-periodic climate cycle lasting 30-50 years, with at least 5 climate shifts over the past 350 years, the last beginning during the 1970's. 

According to the authors, "The correlation of the newly obtained record with the circulation indices of the Southern Hemisphere (SH) shows that the central Antarctic climate is mainly governed by the type of [natural] circulation in the Southern Hemisphere: under conditions of zonal circulation, negative anomalies of temperature and precipitation rate are observed, whereas the sign of the anomalies is positive during meridional circulation."

The paper adds to many others finding nothing unusual or unprecedented regarding the natural and cyclical changes of Antarctic climate over the past century. 
Brown line is air temperature anomaly for Antarctica since 1800 calculated by Schneider et al. Red line is Nov-January [summer] temperature anomalies at Antarctic Vostok station near the South Pole. Yellow line is sea surface temperatures of S Hemisphere. 
Multiple climate shifts in the Southern Hemisphere over the past three centuries based on central Antarctic snow pits and core studies

A.A. EKAYKIN, A.V. KOZACHEK, V.Ya. LIPENKOV, Yu.A. SHIBAEV
Climate and Environment Research Laboratory, Arctic and Antarctic Research Institute, St Petersburg, Russia

ABSTRACT. Based on the results of geochemical and glaciological investigations in snow pits and shallow cores, regional stack series of air temperature in central Antarctica (in the southern part of Vostok Subglacial Lake) were obtained, covering the last 350 years. It is shown that this parameter varied quasi-periodically with a wavelength of 30–50 years. The correlation of the newly obtained record with the circulation indices of the Southern Hemisphere (SH) shows that the central Antarctic climate is mainly governed by the type of circulation in the SH: under conditions of zonal circulation, negative anomalies of temperature and precipitation rate are observed, whereas the sign of the anomalies is positive during meridional circulation. In the 1970s the sign of the relationship between many climatic parameters changed, which is likely related to the rearrangement of the climatic system of the SH. The data suggest that during the past 350 years such events have taken place at least five times. The stable water isotope content of the central Antarctic snow is governed by the summer temperature rather than the mean annual temperature, which is interpreted as the influence of ‘postdepositional’ effects.

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