Dynamics of primary productivity in the northeastern Bay of Bengal over the last 26 000 years
<p>At present, variations of primary productivity (PP) in the Bay of Bengal (BoB) are driven by salinity-related stratification, which is controlled by the Indian summer monsoon (ISM). The relationships between PP, precipitation, and more generally climate in the past are not clearly understoo...
| Published in: | Climate of the Past |
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| Main Authors: | , , , , , |
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-10-01
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| Online Access: | https://cp.copernicus.org/articles/16/1969/2020/cp-16-1969-2020.pdf |
| Summary: | <p>At present, variations of primary productivity (PP) in the Bay of
Bengal (BoB) are driven by salinity-related stratification, which is
controlled by the Indian summer monsoon (ISM). The relationships between PP,
precipitation, and more generally climate in the past are not clearly
understood. Here, we present a new record of PP based on the examination of
coccolithophore assemblages in a 26 000-year sedimentary series retrieved
in the northeastern BoB (core MD77-176). We compare our PP records to
published climate and monsoon records, as well as outputs from numerical
experiments obtained with the Earth system model IPSL-CM5A-LR, including
the marine biogeochemical component PISCES, and with the transient climate
simulation TraCE-21. Our results show that PP was most probably controlled
by nutrient contents and distribution within the upper water column, which
were predominantly influenced by (i) regional river systems between 26 and
19 ka, i.e. when sea level was relatively low and climate was
relatively dry, and (ii) salinity-related stratification over the last 19 kyr, i.e. when sea level rose and more humid conditions prevailed. During
that period, salinity and stratification were directly related to monsoon
precipitation dynamics, which were chiefly forced by both insolation and Atlantic meridional overturning circulation
(AMOC) strength. During Heinrich Stadial 1 and the Younger Dryas, i.e. when the
AMOC collapsed, weaker South Asian precipitation diminished stratification
and enhanced PP. During Bølling–Allerød, i.e. when the AMOC recovered,
stronger South Asian precipitation increased stratification and subdued PP.
Similarly, the precipitation peak recorded around the middle–early Holocene
is consistent with a stronger stratification that drives PP minima.</p> |
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| ISSN: | 1814-9324 1814-9332 |