Variability in Sea-Ice Thickness over the North-Pole from 1977 to 1990

CHANGES in the thickness of polar sea-ice have the potential to provide a signal of climate change, but attempts to identify trends must take into account the range of natural variability. Here we present an analysis of measurements of the subsurface ice thickness (draft) of sea-ice around the North Pole made from 1977 to 1990. These data were collected during six submarine cruises in late April/early May of 1977, 1979, 1986, 1987, 1988 and 1990, and represent the most extensive dataset so far for ice draft in the central Arctic at the same season and location. The results reveal considerable interannual variability both in mean ice draft (+/-1.0 m) and in open-water extent (+/-2.5%). This variability limits the confidence that can be placed in any apparent trends observed for sea-ice thickness or type since the late 1970s, and illustrates the need for a reliable baseline against which to assess future trends.