Premium
Strengthening and Lengthening of the Hawaiian Lee Countercurrent Driven by the Pacific Trade Wind Acceleration
Author(s) -
Nan Feng,
Xue Huijie,
Yu Fei,
Wang Ran
Publication year - 2020
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1029/2020jc016058
Subject(s) - rossby wave , geology , climatology , orographic lift , trade wind , sea level , anomaly (physics) , atmospheric sciences , oceanography , geography , meteorology , physics , precipitation , condensed matter physics
The Hawaiian Lee Countercurrent (HLCC) is a zonal eastward flowing current driven by the orographic wind stress curl (WSC) dipole on the leeside of the Hawaiian Islands, which plays an important role in the regional air‐sea interactions. During the late 1990s and early 2010s, the Pacific trade winds exhibited an unprecedented acceleration with respect to the past century, thus implying a strengthening of the HLCC. Based on satellite observations, we found that the mean velocity and length of the HLCC increased by 53% and 97%, respectively, during the period of the Pacific trade wind acceleration (1999–2014) in comparison to the mean values during the weakened years (1993–1998 and 2015–2018). Correspondingly, the mean heat transport by the HLCC across the International Date Line during the strengthened years increased by 80% in comparison to that before 1999 and after 2014. The sea level anomaly (SLA) variation to the south of the HLCC was found to be the main factor controlling the changes in the HLCC. Local (i.e., near the Hawaiian Islands) and remote WSC both contributed to the SLA variation by exciting westward propagating oceanic Rossby waves, although the former was dominant. Our results also indicate that the dramatically changing HLCC plays an important role in eddy generation along the HLCC path.