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Goldschmidt 2021 Abstract
https://doi.org/10.7185/gold2021.4565
Holocene history of Pacific Water flux
through Bering Strait recorded by
smectite abundance and
ɛ
Nd-signature
in a southern Chukchi Sea cored
sequence
TENGFEI SONG1, CLAUDE HILLAIRE-MARCEL2, ANNE
DE VERNAL2, YANGUANG LIU3 AND RÜDIGER STEIN4
1
Geotop
2
GEOTOP, Université du Québec à Montréal
3
First Institute of Oceanography, Ministry of Natural Resources
4
MARUM - Center for Marine Environmental Sciences and
Faculty of Geosciences, University of Bremen
Presenting Author:
song.tengfei@courrier.uqam.ca
The low-salinity Pacific Water (PW) entering the Arctic
Ocean through Bering Strait (BS) constitutes one third of the
freshwater budget of the Arctic Ocean
[1], which, in its turn,
impacts the Atlantic Meridional Overturning Circulation
(AMOC). This PW flux is tightly controlled by the bathymetry of
BS (~50 m at Present), thus, through time, by sea-level (SL)
changes. In order to document PW flux changes through time,
from sedimentary records, we collected five surface samples
along a transect from BS to the edge of the Chukchi Sea shelf as
a means to calibrate geochemical and mineralogical proxies of
Pacific water fluxes. A core from the Chukchi shelf (ARC6-R09,
168.9°W, 72.0°N) has been used to reconstruct the Holocene
history of this gateway. Measurements included AMS
14C, grain-
size, XRD-clay minerals, as well as the particulate and
exchangeable Nd-isotopes in specific grain-size fractions. So far
smectite content and exchangeable
ɛNd-values decrease
northwards and seem the most sensitive proxies of the PW-flux.
At the coring site, modern-like sediment properties have been
reached progressively, first through a sharp transition from ~ 10
to ~ 4 ka BP, accompanying the deepening of BS with the rising
SL, then by a gentler but continuous "neoglacial" trend towards
modern values, ~14% smectite content and exchangeable
ɛNd-
value ~ -3, thus bearing a very strong Bering Sea signature. This
record also suggests that the major impact of the low-salinity PW
exported from the Arctic Ocean towards the North Atlantic, thus
on the AMOC, was likely achieved at ~ 5 ka BP when Arctic
river discharge was overall stable
[2]. At last, assuming that the
first order parameter governing the PW-flux is the bathymetry of
the sill, a first order estimation of exchangeable
ɛNd-value under
higher SL conditions, such as those of the Last Interglacial,
would indicate a sharp PW-flux increase vs present based on a
direct SL-elevation-
ɛNd relationship calibrated with Holocene
data and the SL rising rate in the last decade.
[1] Woodgate and Aaggard (2005), Geophysical Research
Letters
32, L02602.
[2] Wagner, Lohmann, & Prange (2011),
Global and
Planetary Change 79
, 48-60.