Surface and deep water response to rapid climate changes at the Western Iberian Margin.

Schönfeld, Joachim, Zahn, Rainer and Abreu, Lucia de (2003) Surface and deep water response to rapid climate changes at the Western Iberian Margin. Global and Planetary Change, 36 . pp. 237-264. DOI 10.1016/S0921-8181(02)00197-2.

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Abstract

Rapid climate changes at the onset of the last deglaciation and during Heinrich Event H4 were studied in detail at IMAGES
cores MD95-2039 and MD95-2040 from the Western Iberian margin. A major reorganisation of surface water hydrography,
benthic foraminiferal community structure, and deepwater isotopic composition commenced already 540 years before the Last
Isotopic Maximum (LIM) at 17.43 cal. ka and within 670 years affected all environments. Changes were initiated by meltwater
spill in the Nordic Seas and northern North Atlantic that commenced 100 years before concomitant changes were felt off
western Iberia. Benthic foraminiferal associations record the drawdown of deepwater oxygenation during meltwater and
subsequent Heinrich Events H1 and H4 with a bloom of dysoxic species. At a water depth of 3380 m, benthic oxygen isotopes
depict the influence of brines from sea ice formation during ice-rafting pulses and meltwater spill. The brines conceivably were
a source of ventilation and provided oxygen to the deeper water masses. Some if not most of the lower deep water came from
the South Atlantic. Benthic foraminiferal assemblages display a multi-centennial, approximately 300-year periodicity of oxygen
supply at 2470-m water depth. This pattern suggests a probable influence of atmospheric oscillations on the thermohaline
convection with frequencies similar to Holocene climate variations. For Heinrich Events H1 and H4, response times of surface
water properties off western Iberia to meltwater injection to the Nordic Seas were extremely short, in the range of a few decades
only. The ensuing reduction of deepwater ventilation commenced within 500–600 years after the first onset of meltwater spill.
These fast temporal responses lend credence to numerical simulations that indicate ocean–climate responses on similar and
even faster time scales.

Document Type: Article
Keywords: Heinrich events; Foraminifera; Thermohaline circulation; Ocean currents; RV Marion Dufresne; MD95
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Refereed: Yes
Open Access Journal?: No
Publisher: Elsevier
Projects: IMAGES
Date Deposited: 18 Feb 2008 17:26
Last Modified: 13 Sep 2017 08:50
URI: https://oceanrep.geomar.de/id/eprint/2227

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