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A Shallow Thermocline Bias in the Southern Tropical Pacific in CMIP5/6 Models Linked to Double‐ITCZ Bias
Author(s) -
Samuels Maya,
Adam Ori,
Gildor Hezi
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 - 10.1029/2021gl093818
Subject(s) - thermocline , intertropical convergence zone , coupled model intercomparison project , climatology , geology , proxy (statistics) , climate model , environmental science , oceanography , climate change , precipitation , geography , meteorology , machine learning , computer science
A basin‐wide strong shallow bias in the thermocline of the southern tropical Pacific is found in an ensemble of models from the coupled model intercomparison project phases 5 and 6 (CMIP5/6). The bias is present in over 90% of models examined and is equally represented in CMIP5 and CMIP6 models. In contrast to observations, where the southern thermocline is far deeper than its northern counterpart, models have a hemispherically symmetric tropical thermocline. The shallow thermocline bias is closely linked to the well known double intertropical convergence zone (ITCZ) bias; more so for the physical thermocline (i.e., depth of maximal vertical thermal gradient) than the commonly used 20 ° C isotherm thermocline proxy. A shallow thermocline bias is further found to be associated with climatic conditions including wider separation of double ITCZ peaks, a pronounced cold tongue, and a spurious south equatorial counter current.