Whaling records and changes in Antarctic sea ice: consistency with historical records

Abstract

A claim that there are substantial discrepancies between direct observations of the Antarctic sea-ice edge and the implicit sea-ice edge derived from whaling records is rebutted. The claimeddiscrepancies are shown to arise largely from comparing the two types of information from different dates. A date-corrected comparison shows generally good agreement between the southernmost limit of whaling and the most comprehensive of the early monthly ice charts of Antarctica. The remaining apparent discrepancies are accounted for either by very limited data or the complex nature of the ice edge in the region of the Weddell ice tongue. Correlation of the southernmost limits of whaling with direct observations of the ice edge provides the most powerful calibration of the relationship between them

The Importance of Krill Predation in the Southern Ocean

“…The relationship between whale catch distribution and various physical properties of the Southern Ocean has been noted before (e.g. de la Mare et al 1997, 2009, Ackley et al 2003. This distribution also mirrors the circumpolar distribution of krill , reflecting the broadest scale over which krill predators operate.…”

Assessing recent trends in high-latitude Southern Hemisphere surface climate

“…Some estimates suggest common signals over the whole Southern Ocean, such as the decrease of the ice extent between the 1950s and the late 1970s deduced from whaling records (e.g. 86,87,88 ), but this remains to be confirmed by the analysis of additional observations. The longer records independently support the conclusion that most of the recent changes for any single variable largely result from natural variability, and are not unprecedented over the past two centuries.…”

Paradigm misplaced? Antarctic marine ecosystems are affected by climate change as well as biological processes and harvesting

“…Past changes in sea ice distribution are more difficult to measure and attempts to examine pre-satellite trends have required a degree of ingenuity and the use of proxies. The concept of a significant decline in sea ice in the 1950s-1970s is not as widely discounted as has been suggested (Murphy et al 1995, De La Mare 1997, 2001, Curran et al 2003) and if such a major physical change did occur in the Southern Ocean, there is every reason to suspect that it would have had profound ecological consequences. Correlations have also been reported between ocean temperatures and the breeding success of various other species of upper-trophic level predators (Trathan et al 2006, Forcada et al 2005, Leaper et al 2006.…”