A Southern Ocean trigger for Northwest Pacific ventilation during the Holocene?

Abstract. In this study we report on new non-sea salt calcium (nssCa2+, mineral dust proxy) and sea salt sodium (ssNa+, sea ice proxy) records along the East Antarctic Talos Dome deep ice core in centennial resolution reaching back 150 thousand years (ka) before present. During glacial conditions nssCa2+ fluxes in Talos Dome are strongly related to temperature as has been observed before in other deep Antarctic ice core records, and has been associated with synchronous changes in the main source region (southern South America) during climate variations in the last glacial. However, during warmer climate conditions Talos Dome mineral dust input is clearly elevated compared to other records mainly due to the contribution of additional local dust sources in the Ross Sea area. Based on a simple transport model, we compare nssCa2+ fluxes of different East Antarctic ice cores. From this multi-site comparison we conclude that changes in transport efficiency or atmospheric lifetime of dust particles do have a minor effect compared to source strength changes on the large-scale concentration changes observed in Antarctic ice cores during climate variations of the past 150 ka. Our transport model applied on ice core data is further validated by climate model data. The availability of multiple East Antarctic nssCa2+ records also allows for a revision of a former estimate on the atmospheric CO2 sensitivity to reduced dust induced iron fertilisation in the Southern Ocean during the transition from the Last Glacial Maximum to the Holocene (T1). While a former estimate based on the EPICA Dome C (EDC) record only suggested 20 ppm, we find that reduced dust induced iron fertilisation in the Southern Ocean may be responsible for up to 40 ppm of the total atmospheric CO2 increase during T1. During the last interglacial, ssNa+ levels of EDC and EPICA Dronning Maud Land (EDML) are only half of the Holocene levels, in line with higher temperatures during that period, indicating much reduced sea ice extent in the Atlantic as well as the Indian Ocean sector of the Southern Ocean. In contrast, Holocene ssNa+ flux in Talos Dome is about the same as during the last interglacial, indicating that there was similar ice cover present in the Ross Sea area during MIS 5.5 as during the Holocene.

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Middle Holocene expansion of Pacific Deep Water into the Southern Ocean

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1908138117 ◽

2019 ◽

Vol 117 (2) ◽

pp. 889-894

Author(s):

Torben Struve ◽

David J. Wilson ◽

Tina van de Flierdt ◽

Naomi Pratt ◽

Kirsty C. Crocket

Keyword(s):

Southern Ocean ◽

Ocean Circulation ◽

Deep Water ◽

Water Masses ◽

Ocean Dynamics ◽

Global Ocean ◽

Circulation System ◽

The Holocene ◽

Middle Holocene ◽

Deep Mixing

The Southern Ocean is a key region for the overturning and mixing of water masses within the global ocean circulation system. Because Southern Ocean dynamics are influenced by the Southern Hemisphere westerly winds (SWW), changes in the westerly wind forcing could significantly affect the circulation and mixing of water masses in this important location. While changes in SWW forcing during the Holocene (i.e., the last ∼11,700 y) have been documented, evidence of the oceanic response to these changes is equivocal. Here we use the neodymium (Nd) isotopic composition of absolute-dated cold-water coral skeletons to show that there have been distinct changes in the chemistry of the Southern Ocean water column during the Holocene. Our results reveal a pronounced Middle Holocene excursion (peaking ∼7,000–6,000 y before present), at the depth level presently occupied by Upper Circumpolar Deep Water (UCDW), toward Nd isotope values more typical of Pacific waters. We suggest that poleward-reduced SWW forcing during the Middle Holocene led to both reduced Southern Ocean deep mixing and enhanced influx of Pacific Deep Water into UCDW, inducing a water mass structure that was significantly different from today. Poleward SWW intensification during the Late Holocene could then have reinforced deep mixing along and across density surfaces, thus enhancing the release of accumulated CO2 to the atmosphere.

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Northwest Pacific mid-depth ventilation changes during the Holocene and their implications for the atmosphere-ocean carbon cycle

Quaternary International ◽

10.1016/j.quaint.2012.08.1258 ◽

2012 ◽

Vol 279-280 ◽

pp. 398

Author(s):

Stephan Rella

Keyword(s):

Carbon Cycle ◽

Northwest Pacific ◽

Ocean Carbon Cycle ◽

The Holocene ◽

Ocean Carbon

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Sea surface temperature in the Indian sector of the Southern Ocean over the Late Glacial and Holocene

Climate of the Past ◽

10.5194/cp-16-1451-2020 ◽

2020 ◽

Vol 16 (4) ◽

pp. 1451-1467

Author(s):

Lisa Claire Orme ◽

Xavier Crosta ◽

Arto Miettinen ◽

Dmitry V. Divine ◽

Katrine Husum ◽

...

Keyword(s):

High Resolution ◽

Southern Ocean ◽

Surface Temperature ◽

Sea Surface Temperature ◽

Meridional Overturning Circulation ◽

Sea Surface ◽

Oceanic Circulation ◽

The Holocene ◽

Instrumental Records ◽

Indian Sector

Abstract. Centennial- and millennial-scale variability of Southern Ocean temperature over the Holocene is poorly known, due to both short instrumental records and sparsely distributed high-resolution temperature reconstructions, with evidence for past temperature variations in the region coming mainly from ice core records. Here we present a high-resolution (∼60 year), diatom-based sea surface temperature (SST) reconstruction from the western Indian sector of the Southern Ocean that spans the interval 14.2 to 1.0 ka (calibrated kiloyears before present). During the late deglaciation, the new SST record shows cool temperatures at 14.2–12.9 ka and gradual warming between 12.9 and 11.6 ka in phase with atmospheric temperature evolution. This supports the evolution of the Southern Ocean SST during the deglaciation being linked with a complex combination of processes and drivers associated with reorganisations of atmospheric and oceanic circulation patterns. Specifically, we suggest that Southern Ocean surface warming coincided, within the dating uncertainties, with the reconstructed slowdown of the Atlantic Meridional Overturning Circulation (AMOC), rising atmospheric CO2 levels, changes in the southern westerly winds and enhanced upwelling. During the Holocene the record shows warm and stable temperatures from 11.6 to 8.7 ka followed by a slight cooling and greater variability from 8.7 to 1 ka, with a quasi-periodic variability of 200–260 years identified by spectral analysis. We suggest that the increased variability during the mid- to late Holocene reflects the establishment of centennial variability in SST connected with changes in the high-latitude atmospheric circulation and Southern Ocean convection.

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Sea-level Changes during the Holocene: The Northwest Pacific

Sea Surface Studies ◽

10.1007/978-94-015-1146-9_12 ◽

1987 ◽

pp. 348-374 ◽

Cited By ~ 1

Author(s):

Yoko Ota

Keyword(s):

Sea Level ◽

Northwest Pacific ◽

Sea Level Changes ◽

The Holocene

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Southern Ocean contributions to the Eastern Equatorial Pacific heat content during the Holocene

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2015.05.013 ◽

2015 ◽

Vol 424 ◽

pp. 158-167 ◽

Cited By ~ 12

Author(s):

Julie Kalansky ◽

Yair Rosenthal ◽

Timothy Herbert ◽

Samantha Bova ◽

Mark Altabet

Keyword(s):

Southern Ocean ◽

Heat Content ◽

Equatorial Pacific ◽

The Holocene ◽

Eastern Equatorial Pacific

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Evidence of Southern Ocean influence into the far Northwest Pacific (Northern Emperor Rise) since the Bølling–Allerød warming

Global and Planetary Change ◽

10.1016/j.gloplacha.2020.103315 ◽

2020 ◽

Vol 195 ◽

pp. 103315

Author(s):

Sergey A. Gorbarenko ◽

Xuefa Shi ◽

Yanguang Liu ◽

Jianjun Zou ◽

Olga Yu. Psheneva ◽

...

Keyword(s):

Southern Ocean ◽

Northwest Pacific

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Fragilariopsis kerguelensis size variability from the Indian subtropical Southern Ocean over the last 42 000 years

Antarctic Science ◽

10.1017/s095410201600050x ◽

2016 ◽

Vol 29 (2) ◽

pp. 139-146 ◽

Cited By ~ 5

Author(s):

Sunil Kumar Shukla ◽

Xavier Crosta

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Glacial Period ◽

Last Glacial Period ◽

Subtropical Zone ◽

The Holocene ◽

Last Glacial ◽

Size Variability ◽

The Last Glacial ◽

Valve Area

AbstractIn the open Southern Ocean (SO), both modern and past size changes of the diatom Fragilariopsis kerguelensis appear to be strongly controlled by iron availability. Conversely, sea surface temperatures (SST) and sea ice seasonal dynamics take over in the seasonal sea-ice zone where iron is not limiting. No information exists on F. kerguelensis biometry from the subtropical SO, on the other extreme of the thermal and nutrient gradients. We present here new data on mean valve area of F. kerguelensis (FkergArea) from a sediment core covering the last ~42 cal kyrs from the southern Subtropical Front (SSTF) of the Indian sector of the SO, where iron and silica stocks are thought to have been consistently low over this period. Our results suggest that larger F. kerguelensis valves occurred during the Last Glacial period, and declined during the Holocene period. These findings indicate that more favourable SST, within the F. kerguelensis ecological range, during the Last Glacial period may have enabled F. kerguelensis to make better use of the low silica stocks prevailing in the subtropical zone leading to larger valves. Conversely, declining FkergArea during the deglacial and the Holocene periods may have been a result of higher SST which hampered the utilization of silica.

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