Decadal decrease of Antarctic sea ice extent inferred from whaling records revisited on the basis of historical and modern sea ice records

Article English OPEN
Ackley, Stephen ; Wadhams, Peter ; Comiso, Josefino C. ; Worby, Anthony P. (2003)

In previous work, whaling catch positions were used as a proxy record for the position of the Antarctic sea ice edge and mean sea ice extent greater than the present one spanning 2.8° latitude was postulated to have occurred in the pre-1950s period, compared to extents observed since 1973 from microwave satellite imagery. The previous conclusion of an extended northern latitude for ice extent in the earlier epoch applied only to the January (mid-summer) period. For this summer period, however, there are also possible differences between ship and satellite-derived measurements. Our work showed a consistent summer offset (November– December), with the ship-observed ice edge 1 - 1.5° north of the satellitederived ice edge. We further reexamine the use of whale catch as an ice edge proxy where agreement was claimed between the satellite ice edge (1973–1987) and the ship whale catch positions. This examination shows that, while there may be a linear correlation between ice edge position and whale catch data, the slope of the line deviates from unity and the ice edge is also further north in the whale catch data than in the satellite data for most latitudes. We compare the historical (direct) record and modern satellite maps of ice edge position accounting for these differences in ship and satellite observations. This comparison shows that only regional perturbations took place earlier, without significant deviations in the mean ice extents, from the pre-1950s to the post-1970s. This conclusion contradicts that previously stated from the analysis of whale catch data that indicated Antarctic sea ice extent changes were circumpolar rather than regional in nature between the two periods.
  • References (9)

    Ackley, S. F. & Keliher, T. E. 1976: Antarctic sea ice dynamics and its possible climatic effects. AIDJEX Bull. 33, 53-76.

    Comiso, J., Cavalieri, D. J., Parkinson,C. L. & Gloersen, P. 1997: Passive microwave algorithms for sea ice concentration: a comparison of two techniques. Remote Sens. Environ. 60, 357-384.

    de la Mare, W. K. 1997: Abrupt mid-twentieth-century decline in Antarctic sea ice extent from whaling records, Nature 389, 57-60.

    Mackintosh, N. A. 1972: Sea ice limits. Discovery Rep. 36, 13.

    Mackintosh, N. A. & Herdman, H. F. P. 1940: Distribution of the pack-ice in the Southern Ocean. Discovery Rep. 19, 285-296.

    Thompson, D. W. J. & Solomon, S. 2002: Interpretation of recent southern hemisphere climate change. Science 296, 895-899.

    Vaughan, S. 2000: Can Antarctic sea-ice extent be determined from whaling records? Polar Rec. 36, 345-347.

    Worby, A. P. & Ackley, S. F. 2000: Antarctic research yields circumpolar sea ice thickness data. EOS 81(17), 181, 184- 185.

    Worby, A. P. & Comiso, J. C. 2001: A study of the Antarctic sea ice edge using SSM/I and in-situ observations. In: Proceedings of IEEE 2001 International Geoscience and Remote Sensing Symposium (IGARSS 2001),Sydney, Australia, 9-13 July, 2001. Pp. 163-167. On CD-ROM.

  • Metrics
    No metrics available
Share - Bookmark