Universität zu Köln

Brummer, Geert-Jan A., Metcalfe, Brett ORCID: 0000-0002-5873-9815, Feldmeijer, Wouter, Prins, Maarten Arnoud, van 't Hoff, Jasmijn and Ganssen, Gerald M. (2020). Modal shift in North Atlantic seasonality during the last deglaciation. Clim. Past., 16 (1). S. 265 - 283. GOTTINGEN: COPERNICUS GESELLSCHAFT MBH. ISSN 1814-9332

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Abstract

Changeover from a glacial to an interglacial climate is considered as transitional between two stable modes. Palaeoceanographic reconstructions using the polar foraminifera Neogloboquadrina pachyderma highlight the retreat of the Polar Front during the last deglaciation in terms of both its decreasing abundance and stable oxygen isotope values (delta O-18) in sediment cores. While conventional isotope analysis of pooled N. pachyderma and G. bulloides shells shows a warming trend concurrent with the retreating ice, new single-shell measurements reveal that this trend is composed of two isotopically different populations that are morphologically indistinguishable. Using modern time series as analogues for interpreting downcore data, glacial productivity in the mid-North Atlantic appears limited to a single maximum in late summer, followed by the melting of drifting icebergs and winter sea ice. Despite collapsing ice sheets and global warming during the deglaciation, a second warm population of N. pachyderma appears in a bimodal seasonal succession, separated by the subpolar G. bulloides. This represents a shift in the timing of the main plankton bloom from late to early summer in a deglacial intermediate mode that persisted from the glacial maximum until the start of the Holocene. When seawater temperatures exceeded the threshold values, first the cold (glacial) then the warm (deglacial) populations of N. pachyderma disappeared, whilst G. bulloides with a greater tolerance to higher temperatures persisted throughout the Holocene to the present day in the midlatitude North Atlantic. Single-specimen delta O-18 of polar N. pachyderma reveals a steeper rate of ocean warming during the last deglaciation than appears from conventional pooled delta O-18 average values.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Brummer, Geert-Jan A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Metcalfe, Brett UNSPECIFIED orcid.org/0000-0002-5873-9815 UNSPECIFIED Feldmeijer, Wouter UNSPECIFIED UNSPECIFIED UNSPECIFIED Prins, Maarten Arnoud UNSPECIFIED UNSPECIFIED UNSPECIFIED van 't Hoff, Jasmijn UNSPECIFIED UNSPECIFIED UNSPECIFIED Ganssen, Gerald M. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-345291
DOI:	10.5194/cp-16-265-2020
Journal or Publication Title:	Clim. Past.
Volume:	16
Number:	1
Page Range:	S. 265 - 283
Date:	2020
Publisher:	COPERNICUS GESELLSCHAFT MBH
Place of Publication:	GOTTINGEN
ISSN:	1814-9332
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language OXYGEN-ISOTOPE VARIABILITY; PLANKTONIC-FORAMINIFERA; NEOGLOBOQUADRINA-PACHYDERMA; ABUNDANCE VARIATIONS; WATER TEMPERATURE; SURFACE SALINITY; ICE VOLUME; SEA; OCEAN; RECONSTRUCTION Multiple languages Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/34529