Ocean Wind Wave Climate Responses to Wintertime North Atlantic Atmospheric Transient Eddies and Low Frequency Flow

Abstract

Atmospheric transient eddies and low-frequency flow contribution to the ocean surface wave climate in the North Atlantic during boreal winter is investigated (1980 - 2016). We conduct a set of numerical simulations with a state-of-the-art spectral wave model Wavewatch III forced by decomposed wind fields derived from the ERA-Interim reanalysis (0.7° horizontal resolution). Synoptic-scale processes (2-10 day bandpassed winds) are found to have the largest impact on the formation of wind waves in the western mid-latitude North Atlantic along the North American and western Greenland coasts. The eastern North Atlantic is found to be influenced by the combination of low-frequency forcing (>10 day bandpassed winds) contributing up to 60% and synoptic processes contributing up to 30% to mean wave heights. Mid-latitude storm track variability is found to have a direct relationship with wave height variability on the eastern and western margins of the North Atlantic in particular implying an association between cyclone formation over the North American Eastern Seaboard and wave heights anomalies in the eastern North Atlantic. A shift in wave height regimes defined using an EOF analysis is reflected in the occurrence anomalies in their distribution. Results highlight the dominant role of transient eddies on the ocean surface wave climatology in the mid-latitude eastern North Atlantic both locally and through association with cyclone formation in the western part of the basin. These conclusions are presented and discussed particularly within the context of long-term storm-track shifts projected as a possible response to climate warming over the coming century.