A 250-year periodicity in Southern Hemisphere westerly winds over the last  2600 years

Abstract. Southern Hemisphere westerly airflow has a significant influence on the ocean–atmosphere system of the mid- to high latitudes with potentially global climate implications. Unfortunately, historic observations only extend back to the late 19th century, limiting our understanding of multi-decadal to centennial change. Here we present a highly resolved (30-year) record of past westerly wind strength from a Falkland Islands peat sequence spanning the last 2600 years. Situated within the core latitude of Southern Hemisphere westerly airflow (the so-called furious fifties), we identify highly variable changes in exotic pollen and charcoal derived from South America which can be used to inform on past westerly air strength. We find a period of high charcoal content between 2000 and 1000 cal. years BP, associated with increased burning in Patagonia, most probably as a result of higher temperatures and stronger westerly airflow. Spectral analysis of the charcoal record identifies a pervasive ca. 250-year periodicity that is coherent with radiocarbon production rates, suggesting that solar variability has a modulating influence on Southern Hemisphere westerly airflow. Our results have important implications for understanding global climate change through the late Holocene.

Download Full-text

A 250 year periodicity in Southern Hemisphere westerly winds over the last 2600 years

Climate of the Past Discussions ◽

10.5194/cpd-11-2159-2015 ◽

2015 ◽

Vol 11 (3) ◽

pp. 2159-2180 ◽

Cited By ~ 1

Author(s):

C. Turney ◽

R. Jones ◽

C. Fogwill ◽

J. Hatton ◽

A. N. Williams ◽

...

Keyword(s):

South America ◽

Southern Hemisphere ◽

Late Holocene ◽

Global Climate ◽

Falkland Islands ◽

Late Nineteenth Century ◽

The Core ◽

Atmosphere System ◽

Westerly Winds ◽

Late Nineteenth

Abstract. Southern Hemisphere westerly airflow has a significant influence on the ocean–atmosphere system of the mid- to high-latitudes with potentially global climate implications. Unfortunately historic observations only extend back to the late nineteenth century, limiting our understanding of multi-decadal to centennial change. Here we present a highly resolved (30 yr) record of past westerly air strength from a Falkland Islands peat sequence spanning the last 2600 years. Situated under the core latitude of Southern Hemisphere westerly airflow, we identify highly variable changes in exotic pollen derived from South America which can be used to inform on past westerly air strength and location. The results indicate enhanced airflow over the Falklands between 2000 and 1000 cal. yr BP, and associated with increased burning, most probably as a result of higher temperatures and/or reduced precipitation, comparable to records in South America. Spectral analysis of the charcoal record identifies a 250 year periodicity within the data, suggesting solar variability has a modulating influence on Southern Hemisphere westerly airflow with potentially important implications for understanding global climate change through the late Holocene.

Download Full-text

Late Holocene changes in precipitation in northwest Tasmania and their potential links to shifts in the Southern Hemisphere westerly winds

Global and Planetary Change ◽

10.1016/j.gloplacha.2012.04.005 ◽

2012 ◽

Vol 92-93 ◽

pp. 82-91 ◽

Cited By ~ 19

Author(s):

K.M. Saunders ◽

C. Kamenik ◽

D.A. Hodgson ◽

S. Hunziker ◽

L. Siffert ◽

...

Keyword(s):

Southern Hemisphere ◽

Late Holocene ◽

Westerly Winds ◽

Southern Hemisphere Westerly Winds

Download Full-text

Southern Hemisphere Westerly Winds and Holocene climate variability on sub-Antarctic South Georgia

10.5194/egusphere-egu21-14641 ◽

2021 ◽

Author(s):

Maaike Zwier ◽

Anne Bjune ◽

Willem van der Bilt

Keyword(s):

Climate Variability ◽

Southern Hemisphere ◽

Global Climate ◽

Climatic Variability ◽

Pollen Record ◽

Long Distance ◽

Climate Conditions ◽

South Georgia ◽

Westerly Winds ◽

Southern Hemisphere Westerly Winds

<p>The Southern Hemisphere Westerly Winds play a major role in the global climate system. By driving circulation in the Southern Ocean and its subsequent effect on the upwelling of carbon-rich deep water, the Westerlies affect the oceans ability to take up atmospheric CO<sub>2</sub>. Furthermore, by impacting temperature conditions and moisture availability, the Westerlies act as a first-order control on local environmental conditions. Uncovering long term natural climatic variability in the sub-Antarctic is therefore crucial to understand how the global system might react under future climate changes. Due to the lack of land mass on the Southern Hemisphere, sub-Antarctic islands are essential for studying climate variability in this region; terrestrial records provide valuable insights into both local and regional surface climate conditions. We use a pollen record from Lake Diamond to provide detailed reconstructions of vegetation and climate on sub-Antarctic South Georgia for the last ~9900 years. Westerly Wind strength and position is inferred from long-distance transport of pollen from South America, Africa, and New Zealand. Additionally, changes in relative pollen abundance of native taxa occupying either upland (cold) or lowland (warm) environments are used to infer local climatic variation, supported by additional sedimentological proxies. On South Georgia we find long-distance transported pollen from several South American taxa, mainly Nothofagus, Ephedra and Asteraceae. They show a general increase in abundance throughout the Holocene, with peak influx between 2800 and 1500 cal yr BP, most likely caused by changes in the strength of the Southern Hemisphere Westerly Winds. In both our record and others, this interval is seen as the end of the Neoglacial period.</p>

Download Full-text

Holocene evolution of the Southern Hemisphere westerly winds in transient simulations with global climate models

Climate of the Past Discussions ◽

10.5194/cpd-7-1797-2011 ◽

2011 ◽

Vol 7 (3) ◽

pp. 1797-1824 ◽

Cited By ~ 3

Author(s):

V. Varma ◽

M. Prange ◽

U. Merkel ◽

T. Kleinen ◽

G. Lohmann ◽

...

Keyword(s):

Southern Hemisphere ◽

Climate Models ◽

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Global Climate Models ◽

Orbital Forcing ◽

Westerly Winds ◽

Transient Simulations ◽

Southern Hemisphere Westerly Winds

Abstract. The Southern Hemisphere Westerly Winds (SWW) have been suggested to exert a critical influence on global climate through wind-driven upwelling of deep water in the Southern Ocean and the potentially resulting atmospheric CO2 variations. The investigation of the temporal and spatial evolution of the SWW along with forcings and feedbacks remains a significant challenge in climate research. In this study, the evolution of the SWW under orbital forcing from the mid-Holocene (7 kyr BP) to pre-industrial modern times (250 yr BP) is examined with transient experiments using the comprehensive coupled global climate model CCSM3. In addition, a model inter-comparison is carried out using orbitally forced Holocene transient simulations from four other coupled global climate models. Analyses and comparison of the model results suggest that the annual and seasonal mean SWW were subject to an overall strengthening and poleward shifting trend during the course of the mid-to-late Holocene under the influence of orbital forcing, except for the austral spring season, where the SWW exhibited an opposite trend of shifting towards the equator.

Download Full-text

Holocene evolution of the Southern Hemisphere westerly winds in transient simulations with global climate models

Climate of the Past ◽

10.5194/cp-8-391-2012 ◽

2012 ◽

Vol 8 (2) ◽

pp. 391-402 ◽

Cited By ~ 49

Author(s):

V. Varma ◽

M. Prange ◽

U. Merkel ◽

T. Kleinen ◽

G. Lohmann ◽

...

Keyword(s):

Southern Hemisphere ◽

Climate Models ◽

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Global Climate Models ◽

Orbital Forcing ◽

Westerly Winds ◽

Transient Simulations ◽

Southern Hemisphere Westerly Winds

Abstract. The Southern Hemisphere Westerly Winds (SWW) have been suggested to exert a critical influence on global climate through the wind-driven upwelling of deep water in the Southern Ocean and the potentially resulting atmospheric CO2 variations. The investigation of the temporal and spatial evolution of the SWW along with forcings and feedbacks remains a significant challenge in climate research. In this study, the evolution of the SWW under orbital forcing from the mid-Holocene (7 kyr BP) to pre-industrial modern times (250 yr BP) is examined with transient experiments using the comprehensive coupled global climate model CCSM3. In addition, a model inter-comparison is carried out using orbitally forced Holocene transient simulations from four other coupled global climate models. Analyses and comparison of the model results suggest that the annual and seasonal mean SWW were subject to an overall strengthening and poleward shifting trend during the course of the mid-to-late Holocene under the influence of orbital forcing, except for the austral spring season, where the SWW exhibited an opposite trend of shifting towards the equator.

Download Full-text

Late-Holocene Formation of Lake Michigan Beach Ridges Correlated with a 70-yr Oscillation in Global Climate

Quaternary Research ◽

10.1006/qres.1996.0033 ◽

1996 ◽

Vol 45 (3) ◽

pp. 321-326 ◽

Cited By ~ 15

Author(s):

Paul A. Delcourt ◽

William H. Petty ◽

Hazel R. Delcourt

Keyword(s):

Late Holocene ◽

Lake Michigan ◽

Global Climate ◽

Temperature Oscillation ◽

Beach Ridges ◽

Climate Fluctuations ◽

The Past ◽

Fundamental Part ◽

Atmosphere System ◽

Centennial Time Scale

AbstractA radiocarbon-dated series of 75 beach ridges, formed at regular intervals averaging 72 yr over the past 5400 yr, provides further support for the existence of a 70-yr oscillation in Northern Hemisphere climate, postulated recently from instrument data representing less than two cycles of this climate oscillation. Results from this study lend support to the interpretation that internal variations in the ocean–atmosphere system are an important factor in climate fluctuations on a decadal–centennial time scale. A temperature oscillation with a period of about 70 yr has been a previously unrecognized but fundamental part of the global climate system since at least the middle Holocene.

Download Full-text

How Forestry in the Southern Hemisphere Can Help Address Desertification and Global Climate Change

Journal of Forestry ◽

10.5849/jof.14-071 ◽

2015 ◽

Vol 113 (1) ◽

pp. 72-74

Author(s):

Pablo A. García-Chevesich ◽

Roberto Pizarro ◽

Rodrigo Valdes

Keyword(s):

Climate Change ◽

Southern Hemisphere ◽

Global Climate Change ◽

Global Climate

Download Full-text

Abrupt millennial-scale changes in intensity of Southern Hemisphere westerly winds during marine isotope stages 2–4

Geology ◽

10.1130/g31827.1 ◽

2011 ◽

Vol 39 (5) ◽

pp. 455-458 ◽

Cited By ~ 38

Author(s):

Thomas E. Whittaker ◽

Chris H. Hendy ◽

John C. Hellstrom

Keyword(s):

Southern Hemisphere ◽

Westerly Winds ◽

Southern Hemisphere Westerly Winds ◽

Millennial Scale

Download Full-text

The Role of Oscillating Southern Hemisphere Westerly Winds: Southern Ocean Coastal and Open-Ocean Polynyas

Journal of Climate ◽

10.1175/jcli-d-17-0237.1 ◽

2018 ◽

Vol 31 (3) ◽

pp. 1053-1073 ◽

Cited By ~ 6

Author(s):

Woo Geun Cheon ◽

Chang-Bong Cho ◽

Arnold L. Gordon ◽

Young Ho Kim ◽

Young-Gyu Park

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Southern Hemisphere ◽

Ross Sea ◽

Deep Ocean ◽

Open Ocean ◽

Weddell Sea ◽

Wind Forcing ◽

Westerly Winds ◽

Southern Hemisphere Westerly Winds

Abstract An oscillation in intensity of the Southern Hemisphere westerly winds is a major characteristic of the southern annular mode. Its impact upon the sea ice–ocean interactions in the Weddell and Ross Seas is investigated by a sea ice–ocean general circulation model coupled to an energy balance model for three temporal scales and two amplitudes of intensity. It is found that the oscillating wind forcing over the Southern Ocean plays a significant role both in regulating coastal polynyas along the Antarctic margins and in triggering open-ocean polynyas. The formation of coastal polynya in the western Weddell and Ross Seas is enhanced with the intensifying winds, resulting in an increase in the salt flux into the ocean via sea ice formation. Under intensifying winds, an instantaneous spinup within the Weddell and Ross Sea cyclonic gyres causes the warm deep water to upwell, triggering open-ocean polynyas with accompanying deep ocean convection. In contrast to coastal polynyas, open-ocean polynyas in the Weddell and Ross Seas respond differently to the wind forcing and are dependent on its period. That is, the Weddell Sea open-ocean polynya occurs earlier and more frequently than the Ross Sea open-ocean polynya and, more importantly, does not occur when the period of oscillation is sufficiently short. The strong stratification of the Ross Sea and the contraction of the Ross gyre due to the southward shift of Antarctic Circumpolar Current fronts provide unfavorable conditions for the Ross Sea open-ocean polynya. The recovery time of deep ocean heat controls the occurrence frequency of the Weddell Sea open-ocean polynya.

Download Full-text