Evidence for a prolonged retroflection of the North Brazil Current during glacial stages
The importance of the role played by the tropics in driving and propagating climate change between hemispheres has long been the focus of attention in a bid to evaluate ocean-atmosphere interactions on glacial-interglacial timescales. The Amazon Fan and Ceara Rise in the western equatorial Atlantic...
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ftucl:oai:eprints.ucl.ac.uk.OAI2:1304769 2023-05-15T17:36:16+02:00 Evidence for a prolonged retroflection of the North Brazil Current during glacial stages Wilson, KE Maslin, MA Burns, SJ 2011-02-15 http://discovery.ucl.ac.uk/1304769/ unknown ELSEVIER SCIENCE BV PALAEOGEOGR PALAEOCL , 301 (1-4) 86 - 96. (2011) North Brazil Current Retroflection Amazon freshwater plume delta O-18 analysis Mg/Ca palaeothermometry SEA-SURFACE TEMPERATURE WESTERN TROPICAL ATLANTIC LATE MIOCENE ONSET CLIMATE-CHANGE PLANKTONIC-FORAMINIFERA THERMOHALINE CIRCULATION EQUATORIAL ATLANTIC OXYGEN ISOTOPES AMAZON-RIVER SOUTHERN-OCEAN Article 2011 ftucl 2013-11-10T04:10:19Z The importance of the role played by the tropics in driving and propagating climate change between hemispheres has long been the focus of attention in a bid to evaluate ocean-atmosphere interactions on glacial-interglacial timescales. The Amazon Fan and Ceara Rise in the western equatorial Atlantic Ocean lie directly in the flowpath of the North Brazil Current (NBC) which, as a conduit for the cross-equatorial transport of heat and salinity, is a key component for the heat budget of the North Atlantic. Mg/Ca palaeothermometry and stable oxygen isotope analysis of planktonic foraminifera sampled from 15 sites across the Amazon Fan and Ceara Rise reveal variations in oceanic surface currents and of the dispersal of freshwater from the River Amazon over five timeslices (modern; early Holocene; Younger Dryas; Late Glacial and Marine Isotope Stage 3). Sea surface temperature reconstructions reveal progressive climatic amelioration over the last similar to 30 ka, indicating a temperature increase of similar to 3.2 +/- 1.1 degrees C since the Late Glacial. In conjunction with this warming, values of Delta delta O-18, a proxy for water column stratification indicates increased vertical mixing of the glacial ocean. The spatial distribution of values of delta(18)w (the isotopic composition of ambient seawater) is used to infer surface current variations and demonstrates an oceanward shift in the river outflow plume in cold climates representing a prolongation or possibly permanent continuation in the duration of the seasonal retroflection of the NBC causing the curtailment of cross-equatorial transport. A prolongation of this retroflection could have resulted from a mean southward migration of the southern boundary of the ITCZ. (C) 2011 Elsevier B.V. All rights reserved. Article in Journal/Newspaper North Atlantic Planktonic foraminifera Southern Ocean University College London: UCL Discovery Southern Ocean |
institution |
Open Polar |
collection |
University College London: UCL Discovery |
op_collection_id |
ftucl |
language |
unknown |
topic |
North Brazil Current Retroflection Amazon freshwater plume delta O-18 analysis Mg/Ca palaeothermometry SEA-SURFACE TEMPERATURE WESTERN TROPICAL ATLANTIC LATE MIOCENE ONSET CLIMATE-CHANGE PLANKTONIC-FORAMINIFERA THERMOHALINE CIRCULATION EQUATORIAL ATLANTIC OXYGEN ISOTOPES AMAZON-RIVER SOUTHERN-OCEAN |
spellingShingle |
North Brazil Current Retroflection Amazon freshwater plume delta O-18 analysis Mg/Ca palaeothermometry SEA-SURFACE TEMPERATURE WESTERN TROPICAL ATLANTIC LATE MIOCENE ONSET CLIMATE-CHANGE PLANKTONIC-FORAMINIFERA THERMOHALINE CIRCULATION EQUATORIAL ATLANTIC OXYGEN ISOTOPES AMAZON-RIVER SOUTHERN-OCEAN Wilson, KE Maslin, MA Burns, SJ Evidence for a prolonged retroflection of the North Brazil Current during glacial stages |
topic_facet |
North Brazil Current Retroflection Amazon freshwater plume delta O-18 analysis Mg/Ca palaeothermometry SEA-SURFACE TEMPERATURE WESTERN TROPICAL ATLANTIC LATE MIOCENE ONSET CLIMATE-CHANGE PLANKTONIC-FORAMINIFERA THERMOHALINE CIRCULATION EQUATORIAL ATLANTIC OXYGEN ISOTOPES AMAZON-RIVER SOUTHERN-OCEAN |
description |
The importance of the role played by the tropics in driving and propagating climate change between hemispheres has long been the focus of attention in a bid to evaluate ocean-atmosphere interactions on glacial-interglacial timescales. The Amazon Fan and Ceara Rise in the western equatorial Atlantic Ocean lie directly in the flowpath of the North Brazil Current (NBC) which, as a conduit for the cross-equatorial transport of heat and salinity, is a key component for the heat budget of the North Atlantic. Mg/Ca palaeothermometry and stable oxygen isotope analysis of planktonic foraminifera sampled from 15 sites across the Amazon Fan and Ceara Rise reveal variations in oceanic surface currents and of the dispersal of freshwater from the River Amazon over five timeslices (modern; early Holocene; Younger Dryas; Late Glacial and Marine Isotope Stage 3). Sea surface temperature reconstructions reveal progressive climatic amelioration over the last similar to 30 ka, indicating a temperature increase of similar to 3.2 +/- 1.1 degrees C since the Late Glacial. In conjunction with this warming, values of Delta delta O-18, a proxy for water column stratification indicates increased vertical mixing of the glacial ocean. The spatial distribution of values of delta(18)w (the isotopic composition of ambient seawater) is used to infer surface current variations and demonstrates an oceanward shift in the river outflow plume in cold climates representing a prolongation or possibly permanent continuation in the duration of the seasonal retroflection of the NBC causing the curtailment of cross-equatorial transport. A prolongation of this retroflection could have resulted from a mean southward migration of the southern boundary of the ITCZ. (C) 2011 Elsevier B.V. All rights reserved. |
format |
Article in Journal/Newspaper |
author |
Wilson, KE Maslin, MA Burns, SJ |
author_facet |
Wilson, KE Maslin, MA Burns, SJ |
author_sort |
Wilson, KE |
title |
Evidence for a prolonged retroflection of the North Brazil Current during glacial stages |
title_short |
Evidence for a prolonged retroflection of the North Brazil Current during glacial stages |
title_full |
Evidence for a prolonged retroflection of the North Brazil Current during glacial stages |
title_fullStr |
Evidence for a prolonged retroflection of the North Brazil Current during glacial stages |
title_full_unstemmed |
Evidence for a prolonged retroflection of the North Brazil Current during glacial stages |
title_sort |
evidence for a prolonged retroflection of the north brazil current during glacial stages |
publisher |
ELSEVIER SCIENCE BV |
publishDate |
2011 |
url |
http://discovery.ucl.ac.uk/1304769/ |
geographic |
Southern Ocean |
geographic_facet |
Southern Ocean |
genre |
North Atlantic Planktonic foraminifera Southern Ocean |
genre_facet |
North Atlantic Planktonic foraminifera Southern Ocean |
op_source |
PALAEOGEOGR PALAEOCL , 301 (1-4) 86 - 96. (2011) |
_version_ |
1766135708435611648 |