The Physical Oceanography of the Arctic Mediterranean Sea - Chapter 9: Variability and change

Elsevier, The Physical Oceanography of the Arctic Mediterranean Sea, Exploration, Observations, Interpretations, 2022, Pages 433-477
Bert Rudels

The 1990s heralded a significant change in the exploration, study, and understanding of the oceanography of the Arctic Mediterranean. Before 1990 historical and newly obtained observations were often merged and used together to provide a gradually more accurate and detailed description of the hydrographic structure and the circulation in the Arctic Mediterranean. However, in 1990 Detlef Quadfasel observed and reported that the temperature of the Atlantic layer in the Nansen Basin was about 1°C higher than the temperature found in the historical records. The first SCISEX cruise with USS Pargo 1993 indicated that the salinity and temperature in the upper layer of the Eurasian Basin were higher than previously reported, while the upper layer salinity in the Canada Basin had decreased. The SCISEX expeditions also measured sea ice thickness with upward-looking sonars, and when the newly observed thicknesses were compared with those measured 30 years earlier, they indicated that the mean ice thickness had been reduced by about 40%. Suddenly change rather than constancy became the focus, and observations spread over time, which previously had been used to describe the mean circulation and the mean state, now acquired a time dimension. What changes in forcing could trigger these changes? Were the Arctic Ocean and the Arctic Mediterranean being transformed into new states, or were the observed changes just part of natural variability?