Sammendrag
Recent observational and numerical modeling analyses have led to a number of conceptual models of regional atmospheric circulation features and ice-ocean- atmosphere feedback loops around the northern North Atlantic. In the present study, temporal and geographic aspects of apparent quasi-periodic oscillations around the Atlantic Arctic are investigated on biennial to interdecadal time scales. This is both a confirmatory and exploratory analysis, in which multiple methods are consistently applied to decades-long, spatially-distributed time series of sea ice and climate data. The time series techniques include spectral estimation (maximum entropy method and multi-taper method), cross-spectral and band- pass filtering used in combination. The results indicate a set of overlapping modes of biennial-to-decadal oscillatory behaviour in the regional sea ice cover and climate. Periodicities are found at 12- 14, 7-8, 5.7-5.9, 5, 3-3.5, 2.5-2.9 and 2.2-2.4 years in the air temperature data - cf. the main spectral peaks at 7-8, 5.8, 3.2, 2.8, 2.3-2.4 year in the North Atlantic Oscillation (NAO) index. The highest coherence internally and with respect to the NAO is found for the eastern parts of the study area. Another predominantly eastern feature is the signal at 12-14 years, which is highly coherent within the region. This signal is not found in the NAO, and has an apparent origin in North Atlantic sea-surface temperature fluctuations found previously. The 5-year periodicity has a primarily northern distribution, including the Icelandic sea ice index. This variability appears distinct from the NAO, and speculatively may be linked to a 10-year feedback loop proposed by Mysak and Venegas (1998). A more comprehensive dataset of long oceanographic, sea ice and climate time series is presently being analysed to further improve understanding of interannual to interdecadal scale variability in the Atlantic Arctic, extending back to paleo time scales.
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