Holocene Southern-Ocean Surface Radiocarbon Ages: Implications for Ocean Circulation and Ice-shelf Flow Rates
The Southern Ocean features high surface-water 14C reservoir ages, reflecting substantial upwelling of old deep water and poor air-sea exchange. These high values complicate 14C dating in the circum-Antarctic region, and encode information about past ocean circulation (particularly the rate of deep-...
Main Authors: | , , , |
---|---|
Other Authors: | , , , , |
Format: | Conference Object |
Language: | English |
Published: |
American Geophysical Union
2007
|
Subjects: | |
Online Access: | http://hdl.handle.net/11568/646076 http://abstractsearch.agu.org/meetings/2007/FM/sections/PP/sessions/PP12A/abstracts/PP12A-05.html |
id |
ftunivpisairis:oai:arpi.unipi.it:11568/646076 |
---|---|
record_format |
openpolar |
spelling |
ftunivpisairis:oai:arpi.unipi.it:11568/646076 2024-04-14T08:03:29+00:00 Holocene Southern-Ocean Surface Radiocarbon Ages: Implications for Ocean Circulation and Ice-shelf Flow Rates Henderson G. M. Hall B. L. Kellogg T. B. BARONI, CARLO AGU Henderson, G. M. Hall, B. L. Baroni, Carlo Kellogg, T. B. 2007 ELETTRONICO http://hdl.handle.net/11568/646076 http://abstractsearch.agu.org/meetings/2007/FM/sections/PP/sessions/PP12A/abstracts/PP12A-05.html eng eng American Geophysical Union country:USA place:Washington ispartofbook:2007 AGU Fall Meet 2007 AGU Fall Meeting volume:88 issue:52 firstpage:12 lastpage:12 numberofpages:1 http://hdl.handle.net/11568/646076 http://abstractsearch.agu.org/meetings/2007/FM/sections/PP/sessions/PP12A/abstracts/PP12A-05.html Ice shelve Quaternary geochronology Geochemical tracer Thermohaline Antarctica info:eu-repo/semantics/conferenceObject 2007 ftunivpisairis 2024-03-21T18:45:09Z The Southern Ocean features high surface-water 14C reservoir ages, reflecting substantial upwelling of old deep water and poor air-sea exchange. These high values complicate 14C dating in the circum-Antarctic region, and encode information about past ocean circulation (particularly the rate of deep-water ventilation in the Atlantic). Here we present new results from the Ross Sea that provide a history of Holocene Southern Ocean 14C. Freezing at the base of the McMurdo ice shelf traps sediment (including solitary corals) which is then transported to the ice surface by ice ablation. Forty-five solitary corals from the McMurdo Ice Shelf and from Hells Gate have been dated precisely using U/Th and 14C techniques to provide a detailed reconstruction of surface-water reservoir ages for the past 6,000 years. With the exception of two young samples that show the impact of bomb radiocarbon, other samples indicate a constant 14C reservoir age during this period of 1300±200 years. The constancy of this value is reassuring for studies conducting chronology in the Southern Ocean, or relying on knowledge of deep-water source regions for 14C ventilation ages. It also allows constraints to be placed on changes in the flow of NADW with time, since slower flow leads to older upwelling water in the Southern Ocean. The systematic increase in age of samples with distance from Black Island also allows reconstruction of the flow rate of the McMurdo Ice Shelf. This indicates a constant flow of about 4 m/yr for the last 5000 years, with flow about three times faster before this period. These flow rates compare with short term estimates of flow in the region of about 16 m/yr suggesting that flow may have increased in recent times. Conference Object Antarc* Antarctic Antarctica Ice Shelf McMurdo Ice Shelf NADW Ross Sea Southern Ocean Black Island ARPI - Archivio della Ricerca dell'Università di Pisa Antarctic Southern Ocean Ross Sea McMurdo Ice Shelf ENVELOPE(166.500,166.500,-78.000,-78.000) Hells Gate ENVELOPE(163.800,163.800,-74.850,-74.850) Black Island ENVELOPE(70.100,70.100,-49.440,-49.440) |
institution |
Open Polar |
collection |
ARPI - Archivio della Ricerca dell'Università di Pisa |
op_collection_id |
ftunivpisairis |
language |
English |
topic |
Ice shelve Quaternary geochronology Geochemical tracer Thermohaline Antarctica |
spellingShingle |
Ice shelve Quaternary geochronology Geochemical tracer Thermohaline Antarctica Henderson G. M. Hall B. L. Kellogg T. B. BARONI, CARLO Holocene Southern-Ocean Surface Radiocarbon Ages: Implications for Ocean Circulation and Ice-shelf Flow Rates |
topic_facet |
Ice shelve Quaternary geochronology Geochemical tracer Thermohaline Antarctica |
description |
The Southern Ocean features high surface-water 14C reservoir ages, reflecting substantial upwelling of old deep water and poor air-sea exchange. These high values complicate 14C dating in the circum-Antarctic region, and encode information about past ocean circulation (particularly the rate of deep-water ventilation in the Atlantic). Here we present new results from the Ross Sea that provide a history of Holocene Southern Ocean 14C. Freezing at the base of the McMurdo ice shelf traps sediment (including solitary corals) which is then transported to the ice surface by ice ablation. Forty-five solitary corals from the McMurdo Ice Shelf and from Hells Gate have been dated precisely using U/Th and 14C techniques to provide a detailed reconstruction of surface-water reservoir ages for the past 6,000 years. With the exception of two young samples that show the impact of bomb radiocarbon, other samples indicate a constant 14C reservoir age during this period of 1300±200 years. The constancy of this value is reassuring for studies conducting chronology in the Southern Ocean, or relying on knowledge of deep-water source regions for 14C ventilation ages. It also allows constraints to be placed on changes in the flow of NADW with time, since slower flow leads to older upwelling water in the Southern Ocean. The systematic increase in age of samples with distance from Black Island also allows reconstruction of the flow rate of the McMurdo Ice Shelf. This indicates a constant flow of about 4 m/yr for the last 5000 years, with flow about three times faster before this period. These flow rates compare with short term estimates of flow in the region of about 16 m/yr suggesting that flow may have increased in recent times. |
author2 |
AGU Henderson, G. M. Hall, B. L. Baroni, Carlo Kellogg, T. B. |
format |
Conference Object |
author |
Henderson G. M. Hall B. L. Kellogg T. B. BARONI, CARLO |
author_facet |
Henderson G. M. Hall B. L. Kellogg T. B. BARONI, CARLO |
author_sort |
Henderson G. M. |
title |
Holocene Southern-Ocean Surface Radiocarbon Ages: Implications for Ocean Circulation and Ice-shelf Flow Rates |
title_short |
Holocene Southern-Ocean Surface Radiocarbon Ages: Implications for Ocean Circulation and Ice-shelf Flow Rates |
title_full |
Holocene Southern-Ocean Surface Radiocarbon Ages: Implications for Ocean Circulation and Ice-shelf Flow Rates |
title_fullStr |
Holocene Southern-Ocean Surface Radiocarbon Ages: Implications for Ocean Circulation and Ice-shelf Flow Rates |
title_full_unstemmed |
Holocene Southern-Ocean Surface Radiocarbon Ages: Implications for Ocean Circulation and Ice-shelf Flow Rates |
title_sort |
holocene southern-ocean surface radiocarbon ages: implications for ocean circulation and ice-shelf flow rates |
publisher |
American Geophysical Union |
publishDate |
2007 |
url |
http://hdl.handle.net/11568/646076 http://abstractsearch.agu.org/meetings/2007/FM/sections/PP/sessions/PP12A/abstracts/PP12A-05.html |
long_lat |
ENVELOPE(166.500,166.500,-78.000,-78.000) ENVELOPE(163.800,163.800,-74.850,-74.850) ENVELOPE(70.100,70.100,-49.440,-49.440) |
geographic |
Antarctic Southern Ocean Ross Sea McMurdo Ice Shelf Hells Gate Black Island |
geographic_facet |
Antarctic Southern Ocean Ross Sea McMurdo Ice Shelf Hells Gate Black Island |
genre |
Antarc* Antarctic Antarctica Ice Shelf McMurdo Ice Shelf NADW Ross Sea Southern Ocean Black Island |
genre_facet |
Antarc* Antarctic Antarctica Ice Shelf McMurdo Ice Shelf NADW Ross Sea Southern Ocean Black Island |
op_relation |
ispartofbook:2007 AGU Fall Meet 2007 AGU Fall Meeting volume:88 issue:52 firstpage:12 lastpage:12 numberofpages:1 http://hdl.handle.net/11568/646076 http://abstractsearch.agu.org/meetings/2007/FM/sections/PP/sessions/PP12A/abstracts/PP12A-05.html |
_version_ |
1796299741819043840 |