The flip-side of the North Atlantic Oscillation

• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Chavez; Pacific; North Atlantic; North Atlantic oscillation
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.419.2752; http://www.aslo.org/lo/toc/vol_48/issue_1/0319.pdf

and modal shifts in slope-water circulation patterns Abstract—A large single-year reversal in the phase of the North Atlantic Oscillation (NAO) during 1996 led to a dramatic shift in the slope-water circulation patterns of the northwest (NW) Atlantic. Analyses of time-series data collected from the region over the past half century show that both physical and biological responses are commonly elicited by such phase reversals in the NAO. Here, we use a model developed from time-series data to predict responses of the NW Atlantic slope-water circulation patterns to phase reversals in the NAO. 319 The Atlantic and Pacific Oceans experienced extreme events in ocean climate during the late 1990s. Although overshadowed by the global impacts of the most intense El Nino–Southern Oscillation event on record (Chavez et al. 1999; McPhaden 1999), a large single-year drop in the North Atlantic Oscillation (NAO) index (Hurrell 1995) during 1996 had major regional- and basin-scale impacts for several years throughout the North Atlantic Ocean (Kushnir 1999; Hurrell and Dickson in press). One of the most dramatic consequences of this event was a modal shift in the slopewater circulation patterns of the northwest (NW) Atlantic (MERCINA 2001). By placing these occurrences in the context of time-series data collected from the region over the past half century, it is possible to show that such modal shifts are commonly associated with phase reversals in the NAO (MERCINA 2001). For the past quarter century, the NAO index has exhibited an unusually persistent, positive trend (Langenberg 2000; Hurrell et al. 2001), an observation consistent with the rise of oceanic heat content and models of greenhouse warming