Seasonal and interannual variability of the Odden ice tongue and a study of environmental effects

The Odden ice tongue is an ice cover phenomenon in the Greenland Sea that covers all or part of the area of influence of the Jan Mayen Current and that encloses a bay of open water called Nordbukta. The yearly attributes of the spatial distribution of the Odden from 1979 through 1998 have been quantified in terms of average concentration, standard deviation of ice concentrations, persistence, maximum extent, and anomalies in extent, and the results show vastly different formation characteristics and seasonalities during different years. The monthly average extents of the Odden are shown to have a strong negative correlation with monthly surface air temperatures recorded at Jan Mayen Island and monthly temperatures retrieved from satellite infrared data, with correlation coefficients of 0.74 and 0.89, respectively. Wind effect is also shown to be an important factor at daily and shorter timescales, directly influencing size and shape and sometimes initiating the formation of Nordbukta. The Odden was most extensive in 1979, 1982, 1986, and 1997 and most persistent in 1988, 1989, and 1997 but did not appear in 1984, 1994, and 1995, suggesting decadal periodicity for the 20 year period. With the use of the 75 year temperature record at Jan Mayen Island as a proxy for Odden size, spectral analysis also shows a periodicity of 10–12 years. A correlation study of North Atlantic Oscillation (NAO) indices with extents of the Odden, as derived from satellite data, yields a correlation coefficient of 0.4, which suggests that the interannual variability of the Odden may be influenced but not controlled by NAO. Regression analysis of the Jan Mayen surface temperature record also yields a slight warming (0.06 K decade−1) and a decrease in Odden area (−0.14×104 km2 decade−1) from 1979 to 1996, but during the past 75 years, there has actually been a slight cooling (−0.15 K decade−1), suggesting either that the Odden had actually been smaller in size several decades ago or that it had occurred farther north.