Monday, February 18, 2013

New paper shows Arctic temperatures were warmer than the present multiple times over past 1357 years

A paper published today in Palaeogeography, Palaeoclimatology, Palaeoecology reconstructs temperatures from shells in the North Iceland region of the Arctic Sea over the past 1357 years. The paper demonstrates that temperatures at the end of the record in the year 2000 were not unusual or unprecedented, and were warmer than the present during at least 4 periods over the past 1357 years. Despite claims of climate alarmists that the Arctic should be the first to display a 'fingerprint' of alleged man-made global warming, this new paper adds to many other peer-reviewed papers demonstrating that there is nothing unusual, unnatural, or unprecedented regarding present temperatures in the Arctic.
Bottom graph shows reconstructed temperatures in the year 2000 have been exceeded multiple times over the past 1357 years. Added red horizontal line shows temperatures at the end of the record in the year 2000.
Variability of marine climate on the North Icelandic Shelf in a 1357-year proxy archive based on growth increments in the bivalve Arctica islandica

  • a School of Ocean Sciences, College of Natural Sciences, Bangor University, Menai Bridge, Anglesey, LL59 5AB, Wales, UK
  • b Department of Geological and Atmospheric Sciences, Iowa State University, Ames, IA 50011-3212, USA

Abstract

A multicentennial and absolutely-dated shell-based chronology for the marine environment of the North Icelandic Shelf has been constructed using annual growth increments in the shell of the long-lived bivalve clam Arctica islandica. The region from which the shells were collected is close to the North Atlantic Polar Front and is highly sensitive to the varying influences of Atlantic and Arctic water masses. A strong common environmental signal is apparent in the increment widths, and although the correlations between the growth increment indices and regional sea surface temperatures are significant at the 95% confidence level, they are low (r ~ 0.2), indicating that a more complex combination of environmental forcings is driving growth. Remarkable longevities of individual animals are apparent in the increment-width series used in the chronology, with several animals having lifetimes in excess of 300 years and one, at 507 years, being the longest-lived non-colonial animal so far reported whose age at death can be accurately determined. The sample depth is at least three shells after AD 1175, and the time series has been extended back to AD 649 with a sample depth of one or two by the addition of two further series, thus providing a 1357-year archive of dated shell material. The statistical and spectral characteristics of the chronology are investigated by using two different methods of removing the age-related trend in shell growth. Comparison with other proxy archives from the same region reveals several similarities in variability on multidecadal timescales, particularly during the period surrounding the transition from the Medieval Climate Anomaly to the Little Ice Age.

Highlights

► A shell-based proxy archive for the marine environment north of Iceland. ► The longest (at 1357 years) crossdated shell-based archive so far constructed. ► Includes the longest-lived (at 507 years) non-colonial animal known to science. ► A strong common environmental signal is apparent in the shells. ► There is a possible signal of the timing of the transition from the MCA to the LIA.

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