Abrupt Cooling of Antarctic Surface Waters and Sea Ice Expansion in the South Atlantic Sector of the Southern Ocean at 5000 cal yr B.P.

AbstractAntarctic surface waters were warm and ice free between 10,000 and 5000 cal yr B.P., as judged from ice-rafted debris and microfossils in a piston core at 53°S in the South Atlantic. This evidence shows that about 5000 cal yr B.P., sea surface temperatures cooled, sea ice advanced, and the delivery of ice-rafted detritus (IRD) to the subantarctic South Atlantic increased abruptly. These changes mark the end of the Hypsithermal and onset of Neoglacial conditions. They coincide with an early Neoglacial advance of mountain glaciers in South America and New Zealand between 5400 and 4900 cal yr B.P., rapid middle Holocene climate changes inferred from the Taylor Dome Ice Core (Antarctica), cooling and increased IRD in the North Atlantic, and the end of the African humid period. The near synchrony and abruptness of all these climate changes suggest links among the tropics and both poles that involved nonlinear response to gradual changes in Northern Hemisphere insolation. Sea ice expansion in the Southern Ocean may have provided positive feedback that hastened the end of the Hypsithermal and African humid periods in the middle Holocene.

Download Full-text

Evidence for increased expression of the Amundsen Sea Low over the South Atlantic during the late Holocene

10.5194/cp-2018-11 ◽

2018 ◽

Author(s):

Zoë Thomas ◽

Richard T. Jones ◽

Chris Fogwill ◽

Jackie Hatton ◽

Alan Williams ◽

...

Keyword(s):

Southern Ocean ◽

Late Holocene ◽

Ice Core ◽

South Atlantic ◽

Falkland Islands ◽

The South ◽

Pressure System ◽

Amundsen Sea ◽

Atlantic Sector ◽

Synoptic Conditions

Abstract. The Amundsen Sea Low (ASL) plays a major role in modulating the climate and environment of Antarctica and is of global importance in the Earth system. Unfortunately, a relative dearth of observational data across the Amundsen and Bellingshausen Seas prior to the satellite era (post-1979) limits our understanding of past behaviour and impact of the ASL. The limited proxy evidence for changes in the ASL are primarily limited to the Antarctic where ice core evidence suggests a deepening of the atmospheric pressure system during the late Holocene. However, no data has previously been reported from the northern side of the ASL. Here we report a high-resolution, multi-proxy study of a 5000 year-long peat record from the Falkland Islands (South Atlantic sector of the Southern Ocean), an area sensitive to contemporary ASL dynamics. In combination with climate reanalysis, we find a marked period of wetter, colder conditions most likely the result of enhanced southerly airflow between 5000 and 2500 years ago, and inconsistent with synoptic conditions associated with the ASL today. After 2500 years ago, drier and warmer conditions were established, implying more westerly airflow and the increased projection of the ASL onto the South Atlantic. Our results are in agreement with Antarctic ice core records and suggest the Falkland Islands provide a valuable location for reconstructing atmospheric circulation changes across a large sector of the Southern Ocean on multi-decadal to millennial timescales. The possible role of tropical Pacific in establishing contemporary-like synoptic circulation is explored.

Download Full-text

Evidence for increased expression of the Amundsen Sea Low over the South Atlantic during the late Holocene

Climate of the Past ◽

10.5194/cp-14-1727-2018 ◽

2018 ◽

Vol 14 (11) ◽

pp. 1727-1738 ◽

Cited By ~ 6

Author(s):

Zoë A. Thomas ◽

Richard T. Jones ◽

Chris J. Fogwill ◽

Jackie Hatton ◽

Alan N. Williams ◽

...

Keyword(s):

Southern Ocean ◽

Late Holocene ◽

Ice Core ◽

South Atlantic ◽

Falkland Islands ◽

The South ◽

Pressure System ◽

Amundsen Sea ◽

Atlantic Sector ◽

Concentration Changes

Abstract. The Amundsen Sea Low (ASL) plays a major role in the climate and environment of Antarctica and the Southern Ocean, including surface air temperature and sea ice concentration changes. Unfortunately, a relative dearth of observational data across the Amundsen and Bellingshausen seas prior to the satellite era (post-1979) limits our understanding of the past behaviour and impact of the ASL. The limited proxy evidence for changes in the ASL are primarily restricted to the Antarctic where ice core evidence suggests a deepening of the atmospheric pressure system during the late Holocene. However, no data have previously been reported from the northern side of the ASL. Here we report a high-resolution, multi-proxy study of a 5000-year-long peat record from the Falkland Islands, a location sensitive to contemporary ASL dynamics which modulates northerly and westerly airflow across the southwestern South Atlantic sector of the Southern Ocean. In combination with climate reanalysis, we find a marked period of wetter, colder conditions most likely the result of enhanced southerly airflow between 5000 and 2500 years ago, suggesting limited ASL influence over the region. After 2500 years ago, drier and warmer conditions were established, implying more westerly airflow and the increased projection of the ASL onto the South Atlantic. The possible role of the equatorial Pacific via atmospheric teleconnections in driving this change is discussed. Our results are in agreement with Antarctic ice core records and fjord sediments from the southern South American coast, and suggest that the Falkland Islands provide a valuable location for reconstructing high southern latitude atmospheric circulation changes on multi-decadal to millennial timescales.

Download Full-text

Ice-rafted volcanic ash in the South Atlantic sector of the Southern Ocean during the last 100,000 years

Marine Geology ◽

10.1016/0025-3227(83)90047-6 ◽

1983 ◽

Vol 53 (4) ◽

pp. 291-312 ◽

Cited By ~ 13

Author(s):

David G Smith ◽

Michael T Ledbetter ◽

Paul F Ciesielski

Keyword(s):

Southern Ocean ◽

Volcanic Ash ◽

South Atlantic ◽

The South ◽

Atlantic Sector

Download Full-text

Millennial-scale climate changes on South Georgia, Southern Ocean

Quaternary Research ◽

10.1016/s0033-5894(03)00036-x ◽

2003 ◽

Vol 59 (3) ◽

pp. 470-475 ◽

Cited By ~ 39

Author(s):

Gunhild C. Rosqvist ◽

Pernilla Schuber

Keyword(s):

Southern Hemisphere ◽

North Atlantic ◽

Climate Changes ◽

South Atlantic ◽

The South ◽

Temperature Changes ◽

South Georgia ◽

The North ◽

Suitable Site ◽

Millennial Scale

AbstractThe location of South Georgia (54°S, 36°W) makes it a suitable site for the study of the climatic connections between temperate and polar environments in the Southern Hemisphere. Because the mass balance of the small cirque glaciers on South Georgia primarily responds to changes in summer temperature they can provide records of changes in the South Atlantic Ocean and atmospheric circulation. We use grey scale density, weight-loss-on-ignition, and grain size analyses to show that the proportion of glacially eroded sediments to organic sediments in Block Lake was highly variable during the last 7400 cal yr B.P. We expect that the glacial signal is clearly detectable above noise originating from nonglacial processes and assume that an increase in glacigenic sediment deposition in Block Lake has followed Holocene glacier advances. We interpret proglacial lake sediment sequences in terms of summer climate warming and cooling events. Prominent millennial-scale features include cooling events between 7200 and 7000, 5200 and 4400, and 2400 and 1600 cal yr B.P. and after 1000 cal yr B.P. Comparison with other terrestrial and marine records reveals that the South Georgian record captures all the important changes in Southern Hemisphere Holocene climate. Our results reveal a tentative coupling between climate changes in the South Atlantic and North Atlantic because the documented temperature changes on South Georgia are anti-phased to those in the North Atlantic.

Download Full-text

Comparison of interglacial stages in the South Atlantic sector of the southern ocean for the past 450 kyr: implifications for Marine Isotope Stage (MIS) 11

Global and Planetary Change ◽

10.1016/s0921-8181(99)00069-7 ◽

2000 ◽

Vol 24 (1) ◽

pp. 7-26 ◽

Cited By ~ 114

Author(s):

David A. Hodell ◽

Christopher D. Charles ◽

Ulysses S. Ninnemann

Keyword(s):

Southern Ocean ◽

South Atlantic ◽

Marine Isotope Stage ◽

The South ◽

Atlantic Sector ◽

The Past

Download Full-text

Mesozooplankton biomass distribution in the upper 100 m layer of the Atlantic sector of the Southern Ocean

Antarctic Science ◽

10.1017/s095410209600051x ◽

1996 ◽

Vol 8 (4) ◽

pp. 343-348 ◽

Cited By ~ 2

Author(s):

Jury A. Rudjakov

Keyword(s):

Southern Ocean ◽

Size Range ◽

South Atlantic ◽

Biomass Distribution ◽

The South ◽

Atlantic Sector ◽

Data Centre ◽

Mesozooplankton Biomass ◽

Wet Weight ◽

Oceanographic Data

The distribution of annual mean biomass of mesozooplankton (animals in the size range 0.2–20 mm) in the upper layer (0–100 m) of the Atlantic sector of the Southern Ocean was mapped. The map was constructed from 4216 measurements at 2184 oceanographic stations, from the Russian and Brazilian archive records, from published sources, and from the British Oceanographic Data Centre. The annual mean mesozooplankton biomass value for the South Atlantic is estimated in this study to be 93 mg m−3 wet weight.

Download Full-text