A 2006-2007 Update on Oceanographic Conditions in the Central Arctic Ocean

Trends in central Arctic Ocean conditions are updated with recently gathered data. In the late 1980s and through the 1990s we saw major shifts in the Arctic Ocean. The influence of Atlantic Water in the Arctic Ocean became more widespread and intense and the pattern of water circulation and ice drift shifted, resulting in a more cyclonic circulation. These changes became manifest in the central Arctic near the North Pole as increases in upper ocean salinity and Atlantic Water temperature. They occurred in concert with a decrease in surface atmospheric pressure. With the aim of helping to track such changes, the North Pole Environmental Observatory (NPEO) has been maintained since 2000. Along with an automated drifting station and a deep ocean mooring near the Pole; NPEO conducts airborne hydrographic surveys that track changes along key sections radiating from the Pole. In a related project, several of us have undertaken in situ ocean bottom pressure measurements and the analysis of Gravity Recovery and Climate Experiment (GRACE) data to track changes in the distribution of ocean mass. Hydrographic measurements made by the NPEO show that between 2000 and 2005, oceanographic condition relaxed toward the pre-1990 state. Morison et al [2006] describe these changes and relate them to a decline in the Arctic Oscillation (AO) index. On the basis of in situ and GRACE bottom pressure trends, Morison et al. [2007] argue that shift back to pre-1990s circulation extended over the whole Arctic Ocean. The Spring 2007 NPEO hydrographic surveys and the 2006-2007 bottom pressure data suggest the trend towards pre-1990s conditions has now, once again, reversed. The new observations show greater salinities and bottom pressure near the Pole, indicative of increased Atlantic water presence. Temperatures have increased in the Atlantic Water core along the Eurasian flank of the Lomonosov Ridge. We will explore these most recent changes and their relation to changes in the ice cover and atmospheric conditions. Refs: Morison, J., M. Steele, T. Kikuchi, K. Falkner, and W. Smethie, 2006, Relaxation of central Arctic Ocean hydrography to pre-1990s climatology, Geophys. Res. Lett., 33, L17604, doi:10.1029/2006GL026826. Morison, J., J. Wahr, R. Kwok, and C. Peralta-Ferriz, 2007, Recent trends in Arctic Ocean mass distribution revealed by GRACE, Geophys. Res. Lett., 34, L07602, doi:10.1029/2006GL029016.