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Paleoclimate study of the Southern Ocean using diatom stable isotopes from deep-sea sedimentary records along the last 660 kyr /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Paleoclimate study of the Southern Ocean using diatom stable isotopes from deep-sea sedimentary records along the last 660 kyr // Aya Schneider-Mor.
作者:	Schneider-Mor, Aya,
面頁冊數:	1 electronic resource (91 pages)
附註:	Source: Dissertations Abstracts International, Volume: 71-10, Section: B.
Contained By:	Dissertations Abstracts International71-10B.
標題:	Physical oceanography. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=DP18033
ISBN:	9798635289853

Paleoclimate study of the Southern Ocean using diatom stable isotopes from deep-sea sedimentary records along the last 660 kyr /
Schneider-Mor, Aya,

Paleoclimate study of the Southern Ocean using diatom stable isotopes from deep-sea sedimentary records along the last 660 kyr /Aya Schneider-Mor. - 1 electronic resource (91 pages)

Source: Dissertations Abstracts International, Volume: 71-10, Section: B.

The Southern Ocean plays an important role in the climate system. It acts as a sink for gases that dissolved in its large cold surface water [Broecker, 1982], and it is part of the Thermohaline Circulation (THC) and heat transport mechanism due to the formation of deep waters at the Weddell and Ross seas [Broecker and Denton, 1989; Killworth, 1983; Rahmstorf, 2006; Stocker, 2000], The main primary producers of the Southern Ocean are diatoms, which are responsible for massive deposition of biogenic silica south of the Polar Front region [DeMaster, 2002]. Therefore, studying the Southern Ocean biogenic records, which archive the Southern Ocean climate variations, is the key for understanding its role during global climate changes.The main goals of this study were as follows: 1. To use multi-proxy records to reconstruct climate conditions of the glacial-interglacial cycles at the Antarctic zone. 2. To study the different climate mechanisms that affect the Southern Ocean throughout the past 660 kyr by comparing diatom δ13C to global records of atmospheric CO2 concentration, dust, and other records. 3. To obtain spatial dimensions of productivity and nutrient utilization by comparing the records from two deep sea sediment cores of Ocean Drilling Program (ODP), sites 1093 and 1094, at their different locations at the two edges of the siliceous belt. 4. To study in detail the Terminations periods, which are characterized by rapid changes from glacial to interglacial, and to better understand the sequence of events in the Southern Ocean throughout these transitions. 5. To study the role of salinity changes and melt water events, recorded by δ18OSilica, during glacial periods. These events usually take place before the Terminations' onset and might play an important role in the transition from glacials to interglacials.The work was carried out on two deep sea sediment cores that were recovered from the Atlantic sector of the Southern Ocean, ODP sites 1094 and 1093. Diatoms were purified from the sediment and analyzed for the carbon, nitrogen, and oxygen isotopes retrieved from the diatom organic matter and the diatoms' shells. These records were combined with reconstructions of summer sea surface temperature (SSST) and winter sea-ice (WSI) to establish changes in the surface water characteristics associated with the main climatic events. Both sediment cores are located south of the Polar Front at the northern and southern extreme edges of the siliceous belt. ODP site 1094 is located near the average boundary of the winter sea ice and ODP site 1093 is positioned near the present-day Polar Front. The cores' age models were determined by fit to the 8 D record of Epica Dome C ice core. The oldest age was set at 660 kyr. The δ13C, δ15N of diatom-bound organic matter (δ13CD, δ15ND), δ18O of biogenic silica (δI8OSilica), and the organic matter content (%C, %N) are the longest and most detailed records ever explored at the Southern Ocean. The records of ODP-1094 and ODP-1093 exhibit seven full glacial-interglacial cycles (Marine Stages 1-16) and seven Terminations (I-VII) [Schneider-Mor, et al., 2005; Shemesh, et al, 2002]. All the records from the same sediment core are internally consistent and free of age model artifacts, thus providing the logic behind the lead / lag interpretation of the results.The relationship of the Southern Ocean records to the global climate was explored by comparing the δ13CD-1094 record to the δ18O SPECMAP stack and to the CO2 content record from Vostok and EPICA Dome C ice cores. An excellent agreement was found between δ13CD of ODP site 1094 and the SPECMAP oxygen isotope record, and the Vostok and the EPICA-Dome-C CO2 content, suggesting that δ13CD changes of ODP site 1094 are linked to global temperature change, sea ice coverage, and CO2 (aq) levels. These parameters control most of the δ13CD signal, probably through a reduction in productivity due to extended sea ice cover and lower temperatures during glacials [Schneider-Mor, et al., 2005]. The minor wiggles in the δ13CD-1094 record might result from biological processes, such as growth rate and species abundance that are superimposed on large glacial-interglacial fluctuations [Schneider-Mor, et al., 2005].The underlying mechanism that triggers the glacial-interglacial cycles and reduced the CO2 content is still uncertain. The dust hypothesis claims that an increased dust input to the Southern Ocean surface waters during the glacials released iron to these waters [Brzezinski, et al., 2002 ; Martin, 1990; Matsumoto, et al., 2002] and that increased the productivity and reduced the atmospheric CO2 levels [Martin, 1990]. The silica leakage theory suggests that adding iron to surface water increased the silicic acid transport to the north of the Polar Front and shifted the plankton species to diatoms, thus changing the ocean's alkalinity [Brzezinski, et al. (Abstract shortened by ProQuest).

English

ISBN: 9798635289853Subjects--Topical Terms:

3168433
Physical oceanography.
Subjects--Index Terms:

Deep-sea sediments

Paleoclimate study of the Southern Ocean using diatom stable isotopes from deep-sea sedimentary records along the last 660 kyr /
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520 $a The Southern Ocean plays an important role in the climate system. It acts as a sink for gases that dissolved in its large cold surface water [Broecker, 1982], and it is part of the Thermohaline Circulation (THC) and heat transport mechanism due to the formation of deep waters at the Weddell and Ross seas [Broecker and Denton, 1989; Killworth, 1983; Rahmstorf, 2006; Stocker, 2000], The main primary producers of the Southern Ocean are diatoms, which are responsible for massive deposition of biogenic silica south of the Polar Front region [DeMaster, 2002]. Therefore, studying the Southern Ocean biogenic records, which archive the Southern Ocean climate variations, is the key for understanding its role during global climate changes.The main goals of this study were as follows: 1. To use multi-proxy records to reconstruct climate conditions of the glacial-interglacial cycles at the Antarctic zone. 2. To study the different climate mechanisms that affect the Southern Ocean throughout the past 660 kyr by comparing diatom δ13C to global records of atmospheric CO2 concentration, dust, and other records. 3. To obtain spatial dimensions of productivity and nutrient utilization by comparing the records from two deep sea sediment cores of Ocean Drilling Program (ODP), sites 1093 and 1094, at their different locations at the two edges of the siliceous belt. 4. To study in detail the Terminations periods, which are characterized by rapid changes from glacial to interglacial, and to better understand the sequence of events in the Southern Ocean throughout these transitions. 5. To study the role of salinity changes and melt water events, recorded by δ18OSilica, during glacial periods. These events usually take place before the Terminations' onset and might play an important role in the transition from glacials to interglacials.The work was carried out on two deep sea sediment cores that were recovered from the Atlantic sector of the Southern Ocean, ODP sites 1094 and 1093. Diatoms were purified from the sediment and analyzed for the carbon, nitrogen, and oxygen isotopes retrieved from the diatom organic matter and the diatoms' shells. These records were combined with reconstructions of summer sea surface temperature (SSST) and winter sea-ice (WSI) to establish changes in the surface water characteristics associated with the main climatic events. Both sediment cores are located south of the Polar Front at the northern and southern extreme edges of the siliceous belt. ODP site 1094 is located near the average boundary of the winter sea ice and ODP site 1093 is positioned near the present-day Polar Front. The cores' age models were determined by fit to the 8 D record of Epica Dome C ice core. The oldest age was set at 660 kyr. The δ13C, δ15N of diatom-bound organic matter (δ13CD, δ15ND), δ18O of biogenic silica (δI8OSilica), and the organic matter content (%C, %N) are the longest and most detailed records ever explored at the Southern Ocean. The records of ODP-1094 and ODP-1093 exhibit seven full glacial-interglacial cycles (Marine Stages 1-16) and seven Terminations (I-VII) [Schneider-Mor, et al., 2005; Shemesh, et al, 2002]. All the records from the same sediment core are internally consistent and free of age model artifacts, thus providing the logic behind the lead / lag interpretation of the results.The relationship of the Southern Ocean records to the global climate was explored by comparing the δ13CD-1094 record to the δ18O SPECMAP stack and to the CO2 content record from Vostok and EPICA Dome C ice cores. An excellent agreement was found between δ13CD of ODP site 1094 and the SPECMAP oxygen isotope record, and the Vostok and the EPICA-Dome-C CO2 content, suggesting that δ13CD changes of ODP site 1094 are linked to global temperature change, sea ice coverage, and CO2 (aq) levels. These parameters control most of the δ13CD signal, probably through a reduction in productivity due to extended sea ice cover and lower temperatures during glacials [Schneider-Mor, et al., 2005]. The minor wiggles in the δ13CD-1094 record might result from biological processes, such as growth rate and species abundance that are superimposed on large glacial-interglacial fluctuations [Schneider-Mor, et al., 2005].The underlying mechanism that triggers the glacial-interglacial cycles and reduced the CO2 content is still uncertain. The dust hypothesis claims that an increased dust input to the Southern Ocean surface waters during the glacials released iron to these waters [Brzezinski, et al., 2002 ; Martin, 1990; Matsumoto, et al., 2002] and that increased the productivity and reduced the atmospheric CO2 levels [Martin, 1990]. The silica leakage theory suggests that adding iron to surface water increased the silicic acid transport to the north of the Polar Front and shifted the plankton species to diatoms, thus changing the ocean's alkalinity [Brzezinski, et al. (Abstract shortened by ProQuest).
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650 4 $a Geochemistry. $3 539092
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