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Apparent Periodic and Long‐Term Changes in AAIW and UCDW Properties at Fixed Depths in the Southwest Pacific, With Indications of a Regime Shift in the 1930s
Author(s) -
Thresher Ronald E.,
Fallon Stewart J.
Publication year - 2021
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl092329
Subject(s) - antarctic intermediate water , geology , oceanography , circumpolar deep water , gorgonian , deep sea , deep water , water mass , climatology , atmospheric sciences , coral , north atlantic deep water
Metal/calcium ratios in two long‐lived deep‐sea gorgonian corals ( Lepidisis and Corallium spp.) in the Southwest Pacific evidence periodic decadal variability at depths that correspond to Antarctic Intermediate Water (AAIW) and shallow Upper Circumpolar Deep Water, and a shift in the mid‐1930s to late‐1930s in mean ambient temperatures, barium/silicate concentrations and possibly pH, the rate at which these properties change over time, and the relationship between temperatures at fixed depth and the Southern Annular Mode (SAM). The decadal periodicity, which is evident in other biological indices in the study area, can be accounted for by water mass heave on the order of 100–150 m, which is consistent with observed scales of variability in the AAIW. The proximate and ultimate causes of the midcentury shifts are unclear, but could be related to suggested mid‐20th century changes in climate parameters globally and, more specifically, in the subpolar SW Pacific.