Alkenone sea surface temperature in the Southern Ocean for the last two deglaciations

Ikehara, Masaaki; Kawamura, Kimitaka; Ohkouchi, Naohiko; Kimoto, Katsunori; Nakamura, Toshio; Oba, Tadamichi; Taira, Asahiko

doi:10.1029/97gl00429

Cited by 49 publications

(45 citation statements)

References 24 publications

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“…at 104 and 97 ka (during substage 5c), and at 78 ka (in the middle of substage 5a). The 118.5-ka event could be the same as recognized in other areas of the Southern Ocean (Pichon et al, 1992;Ikehara et al, 1997;Ninnemann et al, 1999), while the 9-ka event could be equivalent to the 8.2-ka cooling event of the North Atlantic (Alley et al, 1997;von Grafenstein et al, 1998). The recognition of these events in our sedimentary record from the Southern Ocean witnesses their importance as global, or at least hemispheric, events not strictly limited to polar ice cores and/or areas surrounding the North Atlantic.…”

Section: Conclusionŝmentioning

confidence: 88%

“…118.5 ka) could be the same cooling event recognized in the Southern Ocean using di¡erent climatic proxies, i.e. diatom- (Pichon et al, 1992) and alkenone-based SSST estimates (Ikehara et al, 1997), and N 13 C of benthic foraminifera (Ninnemann et al, 1999).…”

Section: Climate Variability and Optima (Mis 1 And 5)mentioning

confidence: 99%

“…Di¡erent symbols have been assigned to stations according to which radiolarian assemblage reaches the higher factor component value at that station (also see Tables 2 and 3): factor 1 = ¢lled circle, factor 2 = open circle, factor 3 = square, factor 4 = asterisk. around 120 ka, possibly a Southern Ocean event (Ikehara et al, 1997). However, the geographical extent of these events is still not clear, with debate continuing on whether they were of regional or global signi¢cance.…”

Section: Introductionmentioning

confidence: 99%

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Radiolarian-based paleotemperatures during the last 160 kyr at ODP Site 1089 (Southern Ocean, Atlantic Sector)

Cortese

Abelmann

2002

Palaeogeography, Palaeoclimatology, Palaeoecology

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Two cores, Site 1089 (ODP Leg 177) and PS2821-1, recovered from the same location (40 ‡56PS; 9 ‡54PE) at the Subtropical Front (STF) in the Atlantic Sector of the Southern Ocean, provide a high-resolution climatic record, with an average temporal resolution of less than 600 yr. A multi-proxy approach was used to produce an age model for Core PS2821-1, and to correlate the two cores. Both cores document the last climatic cycle, from Marine Isotopic Stage 6 (MIS 6, ca. 160 kyr BP, ka) to present. Summer sea-surface temperatures (SSSTs) have been estimated, with a standard error of ca. þ 1.16 ‡C, for the down core record by using Q-mode factor analysis (Imbrie and Kipp method). The paleotemperatures show a 7 ‡C warming at Termination II (last interglacial, transition from MIS 6 to MIS 5). This transition from glacial to interglacial paleotemperatures (with maximum temperatures ca. 3 ‡C warmer than present at the core location) occurs earlier than the corresponding shift in N 18 O values for benthic foraminifera from the same core; this suggests a lead of Southern Ocean paleotemperature changes compared to the global ice-volume changes, as indicated by the benthic isotopic record. The climatic evolution of the record continues with a progressive temperature deterioration towards MIS 2. High-frequency, millennial-scale climatic instability has been documented for MIS 3 and part of MIS 4, with sudden temperature variations of almost the same magnitude as those observed at the transitions between glacial and interglacial times. These changes occur during the same time interval as the Dansgaard^Oeschger cycles recognized in the N 18 O ice record of the GRIP and GISP ice cores from Greenland, and seem to be connected to rapid changes in the STF position in relation to the core location. Sudden cooling episodes ('Younger Dryas (YD)-type' and 'Antarctic Cold Reversal (ACR)-type' of events) have been recognized for both Termination I (ACR-I and YD-I events) and II (ACR-II and YD-II events), and imply that our core is located in an optimal position in order to record events triggered by phenomena occurring in both hemispheres. Spectral analysis of our SSST record displays strong analogies, particularly for high, sub-orbital frequencies, to equivalent records from Vostok (Antarctica) and from the Subtropical North Atlantic ocean. This implies that the climatic variability of widely separated areas (the Antarctic continent, the Subtropical North Atlantic, and the Subantarctic South Atlantic) can be strongly coupled and co-varying at millennial time scales (a few to 10-ka periods), and eventually induced by the same triggering mechanisms. Climatic variability has also been documented for supposedly warm and stable interglacial intervals (MIS 1 and 5), with several cold events which can be correlated to other Southern Ocean and North Atlantic sediment records. ß

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Section: Conclusionŝmentioning

confidence: 88%

Section: Climate Variability and Optima (Mis 1 And 5)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Radiolarian-based paleotemperatures during the last 160 kyr at ODP Site 1089 (Southern Ocean, Atlantic Sector)

Cortese

Abelmann

2002

Palaeogeography, Palaeoclimatology, Palaeoecology

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“…The strongest anomalies occur in the southern California borderland region (ODP 893 and ODP 1012), which today represents the boundary between the cold, equatorward-flowing California Current, and subtropical waters which flow northward seasonally . around 28 C. In addition, the alkenone dataset from the southern hemisphere (Ikehara et al, 1997;Pahnke and Sachs, 2006;Pelejero et al, 2006) lacks the data density now available for much of the northern hemisphere.…”

Section: Millennial-scale Events Of the Late Pleistocene And Last Glamentioning

confidence: 96%

Alkenone Paleotemperature Determinations

Herbert

2014

Treatise on Geochemistry

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“…This ratio is generally unaltered through the food web in water column and early diagenesis in sediments (Prahl and Muehlausen, 1989). Longchain alkenones have now been explored in sedimentary records to monitor SST variations from decadal scale El Niño events (McCaffrey et al, 1990;Kennedy and Brassell, 1992) to millenial scale climate changes (Brassell et al, 1986;Prahl and Muehlausen, 1989;Sikes et al, 1991;Eglinton et al, 1992;Brassell, 1993;Rostek et al, 1993;Zhao et al, 1993;Ohkouchi et al, 1994;Schneider et al, 1995;Ikehara et al, 1997;Madureira et al, 1997;Villanueva et al, 1998). In this paper, we investigate the evolution of SST in the Sea of Okhotsk from 16 kyrs BP to the present using alkenone unsaturation data obtained from analysis of a sediment core.…”

Section: Introductionmentioning

confidence: 99%

Alkenone sea surface temperature in the Okhotsk Sea for the last 15 kyr.

et al. 2000

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A sediment core collected from the Sea of Okhotsk, a marginal sea of the western North Pacific, has been analyzed for alkenones to reconstruct changes in the sea surface temperatures (SST) over the last 15 kyrs. A comparison of the core-top U 37 K′ value with the modern surface temperatures indicates that alkenones are produced at present in summer-fall season, a production seasonality probably identical to the one prevailing in the past, as suggested by evidences of enhanced sea ice cover and subsequent limitation of the phytoplankton growth period to summer-fall at the glacial/deglacial transition. The alkenone downcore profile indicated that summer SST at the early deglaciation period (15 kyrs BP) were around 5°C lower than today (ca. 11°C). A rapid SST increase (more than 3°C) was found to occur from 13

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Alkenone sea surface temperature in the Southern Ocean for the last two deglaciations

Cited by 49 publications

References 24 publications

Radiolarian-based paleotemperatures during the last 160 kyr at ODP Site 1089 (Southern Ocean, Atlantic Sector)

Radiolarian-based paleotemperatures during the last 160 kyr at ODP Site 1089 (Southern Ocean, Atlantic Sector)

Alkenone Paleotemperature Determinations

Alkenone sea surface temperature in the Okhotsk Sea for the last 15 kyr.

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