North Atlantic climate variability: The role of the North Atlantic Oscillation

摘要: Abstract Marine ecosystems are undergoing rapid change at local and global scales. To understand these changes, including the relative roles of natural variability anthropogenic effects, to predict future state marine requires quantitative understanding physics, biogeochemistry ecology oceanic systems mechanistic levels. Central this is role played by dominant patterns or “modes” atmospheric variability, which orchestrate coherent variations in climate over large regions with profound impacts on ecosystems. We review spatial structure extratropical Northern Hemisphere and, specifically, focus modes North Atlantic. A leading pattern weather Atlantic Oscillation (NAO). The NAO refers a redistribution mass between Arctic subtropical Atlantic, swings from one phase another producing changes surface air temperature, winds, storminess precipitation as well adjacent continents. also affects ocean through heat content, gyre circulations, mixed layer depth, salinity, high latitude deep water formation sea ice cover. Thus, indices have become widely used document how mode alters functioning There no unique way, however, define NAO. Several approaches discussed both linear (e.g., principal component analysis) nonlinear cluster techniques. former, been most used, assume preferred circulation states come pairs, anomalies opposite polarity same structure. In contrast, techniques search for recurrent specific amplitude sign. They reveal, instance, asymmetries different phases that likely important ecological studies. It follows there universally accepted index describe temporal evolution common measures presented compared. All reveal time scale NAO: occur winter next decade next. amount within-season so winters cannot be characterized solely canonical better responds external forcing, temperature tropics, stratospheric influences, increasing greenhouse gas concentrations, crucial current debate change.