Glacial North Atlantic Millennial Variability over the Last 300,000 Years
The hematite-stained grain (HSG) proxy method, commonly employed by the late G.C. Bond to detect the "1500-year cycle" in North Atlantic climate, is reproduced and verified for the first time. The exact method is compiled from various sources and presented in Chapter 1. In Chapter 2, an HSG...
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ftdukeunivdsp:oai:localhost:10161/910 2023-11-12T04:17:55+01:00 Glacial North Atlantic Millennial Variability over the Last 300,000 Years Obrochta, Stephen Crowley, Thomas J 2008-11-26 20475702 bytes application/pdf https://hdl.handle.net/10161/910 en_US eng https://hdl.handle.net/10161/910 Geology Dissertation 2008 ftdukeunivdsp 2023-10-17T09:45:42Z The hematite-stained grain (HSG) proxy method, commonly employed by the late G.C. Bond to detect the "1500-year cycle" in North Atlantic climate, is reproduced and verified for the first time. The exact method is compiled from various sources and presented in Chapter 1. In Chapter 2, an HSG record from classic North Atlantic DSDP Site 609 is reconsidered. While the Site 609 HSG record was initially interpreted to exhibit 1500-year variability, it did not actually contain spectral power at the 1500-year band. The chronology for Site 609 is based on radicarbon dates to 26 ka, beyond which the sea surface temperature record is matched to the record of air temperature variations over Greenland from the GISP2 ice core. However, it is now evident that the lack of spectral power at the primary period of the observed fluctuation was likely due to the GISP2 chronology, which has been subsequently shown to become progressively deficient over the course of the last glaciation. Updating the Site 609 chronology to the latest chronology for the virtually complete NGRIP Greenland ice core, which is based on layer counting to 60 ka, results in 99% significant spectral power at a 1/1415 year frequency. In Chapter 3, the classic Site 609 lithic records are extended to the previous two glaciations, glacial Stages 6 and 8, at IODP Site U1308 (reoccupied Site 609). The "1500-year cycle" is not detected within Stage 6, perhaps indicating that D-O Events were not manifest in a similar fashion, if at all. Heinrich Event are also not detected, indicating relative stability of the North American Laurentide Ice Sheet during Stage 6. As a result, individual North Atlantic sites recorded lower-amplitude, asynchronous hydrographic changes. The SST proxy record at Site U1308 during Stage 6 primarily records intermediate temperatures. The subtle SST changes detected likely indicate local as opposed to basin-scale changes related to the migration of oceanic frontal boundaries. During Stage 6, benthic δ13C changes are of lower amplitude than Stages 2 ... Doctoral or Postdoctoral Thesis Greenland Greenland ice core ice core Ice Sheet NGRIP North Atlantic Duke University Libraries: DukeSpace Greenland |
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Open Polar |
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Duke University Libraries: DukeSpace |
op_collection_id |
ftdukeunivdsp |
language |
English |
topic |
Geology |
spellingShingle |
Geology Obrochta, Stephen Glacial North Atlantic Millennial Variability over the Last 300,000 Years |
topic_facet |
Geology |
description |
The hematite-stained grain (HSG) proxy method, commonly employed by the late G.C. Bond to detect the "1500-year cycle" in North Atlantic climate, is reproduced and verified for the first time. The exact method is compiled from various sources and presented in Chapter 1. In Chapter 2, an HSG record from classic North Atlantic DSDP Site 609 is reconsidered. While the Site 609 HSG record was initially interpreted to exhibit 1500-year variability, it did not actually contain spectral power at the 1500-year band. The chronology for Site 609 is based on radicarbon dates to 26 ka, beyond which the sea surface temperature record is matched to the record of air temperature variations over Greenland from the GISP2 ice core. However, it is now evident that the lack of spectral power at the primary period of the observed fluctuation was likely due to the GISP2 chronology, which has been subsequently shown to become progressively deficient over the course of the last glaciation. Updating the Site 609 chronology to the latest chronology for the virtually complete NGRIP Greenland ice core, which is based on layer counting to 60 ka, results in 99% significant spectral power at a 1/1415 year frequency. In Chapter 3, the classic Site 609 lithic records are extended to the previous two glaciations, glacial Stages 6 and 8, at IODP Site U1308 (reoccupied Site 609). The "1500-year cycle" is not detected within Stage 6, perhaps indicating that D-O Events were not manifest in a similar fashion, if at all. Heinrich Event are also not detected, indicating relative stability of the North American Laurentide Ice Sheet during Stage 6. As a result, individual North Atlantic sites recorded lower-amplitude, asynchronous hydrographic changes. The SST proxy record at Site U1308 during Stage 6 primarily records intermediate temperatures. The subtle SST changes detected likely indicate local as opposed to basin-scale changes related to the migration of oceanic frontal boundaries. During Stage 6, benthic δ13C changes are of lower amplitude than Stages 2 ... |
author2 |
Crowley, Thomas J |
format |
Doctoral or Postdoctoral Thesis |
author |
Obrochta, Stephen |
author_facet |
Obrochta, Stephen |
author_sort |
Obrochta, Stephen |
title |
Glacial North Atlantic Millennial Variability over the Last 300,000 Years |
title_short |
Glacial North Atlantic Millennial Variability over the Last 300,000 Years |
title_full |
Glacial North Atlantic Millennial Variability over the Last 300,000 Years |
title_fullStr |
Glacial North Atlantic Millennial Variability over the Last 300,000 Years |
title_full_unstemmed |
Glacial North Atlantic Millennial Variability over the Last 300,000 Years |
title_sort |
glacial north atlantic millennial variability over the last 300,000 years |
publishDate |
2008 |
url |
https://hdl.handle.net/10161/910 |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland Greenland ice core ice core Ice Sheet NGRIP North Atlantic |
genre_facet |
Greenland Greenland ice core ice core Ice Sheet NGRIP North Atlantic |
op_relation |
https://hdl.handle.net/10161/910 |
_version_ |
1782334673540612096 |