In:
Climate of the Past, Copernicus GmbH, Vol. 18, No. 4 ( 2022-05-02), p. 961-973
Abstract:
Abstract. It has been hypothesized that global temperature trends are tightly linked
to tropical thermocline depth, and that thermocline shoaling played a
crucial role in the intensification of late Pliocene Northern Hemisphere
glaciation. The Pliocene thermocline evolution in the Pacific Ocean is well
documented and supports this hypothesis, but thermocline records from the
tropical Atlantic Ocean are limited. We present new planktonic foraminiferal
Mg/Ca, δ18O, and δ13C records from the late Pliocene interval at Ocean Drilling Program Site 959 in the Eastern
Equatorial Atlantic (EEA), which we use to reconstruct ocean temperatures
and relative changes in salinity and thermocline depth. Data were generated
using surface-dwelling Globigerinoides ruber and subsurface-dwelling Neogloboquadrina dutertrei. Reduced gradients between
the surface and subsurface records indicate deepening of the EEA thermocline
at the end of the mid-Piacenzian Warm Period (mPWP; ∼ 3.3–3.0 Ma). We connect our late Pliocene records to previously published early
Pliocene δ18O data from Site 959 and compare these to the Site 1000 in the Caribbean Sea. Over the course of the Pliocene, thermocline changes in the EEA and Caribbean Sea follow similar patterns, with prominent
step-wise thermocline deepening between ∼ 5.5 and 4.0 Ma and
gradual shoaling up to the mPWP, followed by minor deepening at the end of
the mPWP. The tropical thermocline depth evolution of the tropical Atlantic
differs from the Pacific, which is characterized by gradual basin-wide
shoaling across the Pliocene. These results potentially challenge the
hypothesized link between tropical thermocline depth and global climate. The
mechanisms behind the periodically divergent Pacific and Atlantic
thermocline movements remain speculative. We suggest that they are related
to basin geometry and heterogenous temperature evolutions in regions from
where thermocline waters are sourced. A positive feedback loop between
source region temperature and tropical cyclone activity may have amplified
tropical thermocline adjustments.
Type of Medium:
Online Resource
ISSN:
1814-9332
DOI:
10.5194/cp-18-961-2022
DOI:
10.5194/cp-18-961-2022-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2022
detail.hit.zdb_id:
2217985-9
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