Gyre-scale atmospheric pressure variations and their relation to 19th and 20th century sea level rise

Abstract

Most of the long tide gauge records in the North Atlantic and North Pacific commonly used to estimate global sea level rise and acceleration display a marked difference in behavior in the late 1800's - early 1900's compared to the latter half of the 20th century. The rates of sea level rise tend to be lower in the 19th compared to 20th century. We show this behavior may be related to long-term, gyre-scale surface pressure variations similar to those associated with the Northern Annular Mode. As sea level pressure increases (decreases) at decadal and longer timescales at the centers of the subtropical atmospheric gyres, sea level trends along the eastern margins in each ocean basin decrease (increase). This is not an isostatic response; the scaling between local surface pressure and sea level at interannual and longer timescales is 3 to 6 times greater than expected by that mechanism. Rather, it appears to be the result of large, possibly gyre-scale changes in ocean circulation. Some evidence is also presented indicating slow, ∼2 cm/ sec, westward propagation of sea level changes in the Atlantic from the west coast of Europe to the east coast of the U.S. which produce the decadal variability seen there. Copyright 2007 by the American Geophysical Union.