Monday, February 25, 2013

New paper finds Antarctic meltwater was much higher in the past

A new paper published in The Holocene finds the Antarctic interior was warmer than the present over a period lasting about 2000 years, from 4300 to 2250 years ago. The paper surveys 3 lakes within 10° of the South Pole and finds meltwater levels were up to 69.5 meters higher than the present, which the authors "interpreted as being the result of an increased number of meltwater events and/or degree-days above freezing, relative to the present." The paper adds to many other peer-reviewed papers demonstrating that Antarctica has warmed for prolonged periods to temperatures higher than the present, and that there is nothing unusual, unnatural, or unprecedented in regard to present day temperatures. 

Lake highstands in the Pensacola Mountains and Shackleton Range 4300–2250 cal. yr BP: Evidence of a warm climate anomaly in the interior of Antarctica

  1. Dominic A Hodgson1
  2. Michael J Bentley2
  1. 1British Antarctic Survey, UK
  2. 2University of Durham, UK
  1. Dominic A Hodgson, British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK. Email: daho@bas.ac.uk

Abstract

We surveyed and dated the former shorelines of one lake in the Shackleton Range and two lakes in the Pensacola Mountains, situated inland of the Weddell Sea embayment Antarctica between 80° and 85°S. These are amongst the highest latitude lakes in the Antarctic and are located in areas where there is little or no Holocene climate and hydrological information. Surveys of the lake shorelines show that past water levels have been up to 15.7, 17.7 and 69.5 m higher than present in the three study lakes. AMS radiocarbon dating of lake-derived macrofossils showed that there was a sustained period of higher water levels from approximately 4300 and until sometime after 2250 cal. yr before the present. This is interpreted as being the result of an increased number of meltwater events and/or degree-days above freezing, relative to the present. The closest comparable ice cores from the Dominion Range in the Transantarctic Mountains (85°S, 166°E) and the Plateau Remote ice core on the continental East Antarctic Ice Sheet (84°S, 43°E) also provide some evidence of a warmer period beginning at c. 4000–3500 yr BP and ending after 2000–1500 yr BP, as does a synthesis of oxygen isotope data from five Antarctic ice cores. This suggests that the well-documented mid- to late-Holocene warm period, measured in many lake and marine sediments around the coast of Antarctica, extended into these regions of the continental interior.

2 comments:

  1. 4000 - 3500YBP is the end of the Minoan Warm Period, I'd guess. The 2000 - 1500 YBP would be the end of the Roman Warm Period. Close enough?

    Hemispheric cycling?

    ReplyDelete
    Replies
    1. I think it is probably close enough to be considered part of those warming periods.

      Delete

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