A quick response of the equatorial ocean to Antarctic sea ice/salinity anomalies

Abstract

The potential mechanisms for a quick response of the equatorial ocean to processes occurring in the high‐latitude Southern Ocean have been investigated. In the Southern Ocean at the Drake Passage latitudes, there is an zonally unbounded “channel”, the Antarctic Circumpolar Current Belt (ACCB). It is demonstrated that in a multiconnected domain such as the ACCB, signals generated by anomalies in the Southern Ocean sea ice cover/salinity distribution can propagate in a wave‐like manner in the form of fast moving barotropic Rossby waves. A disturbance induced near the Drake Passage is demonstrated to generate a Rossby wave that propagates across the Pacific in only a few days. This signal is reflected at the western boundary of the Pacific and generates an equatorward propagating coastally trapped Kelvin wave. The resulting temperature anomaly moves northward along the western coastline up to the vicinity of the equator and increases in amplitude over time. The anomaly in the western edge of equatorial Pacific then begins to propagate eastward along the equator as a trapped equatorial wave. After about 2–3 months this wave reaches the eastern coast, reflects, and generates the coastal trapped wave, which propagates north and south along the coastline in both hemispheres. This process is suggested as one possible direct mechanism by which the extratropical ocean can induce anomalies in the equatorial ocean.