Browsing by Author "Perren, B"
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- ItemHolocene dynamics of the Southern Hemisphere westerly winds and possible links to CO2 outgassing(Springer Nature, 2018-07-23) Saunders, KM; Roberts, SJ; Perren, B; Butz, C; Sime, L; Davies, S; van Nieuwenhuyze, W; Grosjean, M; Hodgson, DAThe Southern Hemisphere westerly winds (SHW) play an important role in regulating the capacity of the Southern Ocean carbon sink. They modulate upwelling of carbon-rich deep water and, with sea ice, determine the ocean surface area available for air–sea gas exchange. Some models indicate that the current strengthening and poleward shift of these winds will weaken the carbon sink. If correct, centennial- to millennial-scale reconstructions of the SHW intensity should be linked with past changes in atmospheric CO2, temperature and sea ice. Here we present a 12,300-year reconstruction of wind strength based on three independent proxies that track inputs of sea-salt aerosols and minerogenic particles accumulating in lake sediments on sub-Antarctic Macquarie Island. Between about 12.1 thousand years ago (ka) and 11.2 ka, and since about 7 ka, the wind intensities were above their long-term mean and corresponded with increasing atmospheric CO2. Conversely, from about 11.2 to 7.2 ka, the wind intensities were below their long-term mean and corresponded with decreasing atmospheric CO2. These observations are consistent with model inferences of enhanced SHW contributing to the long-term outgassing of CO2 from the Southern Ocean. © 2021 Springer Nature Limited
- ItemLate quaternary changes in the westerly winds over the Southern Ocean – a progress report(VII Southern Connection Congress 2016, 2016-01-18) Hodgson, DA; Roberts, S; Perren, B; Saunders, KM; Verleyen, E; van Nieuwenhuyze, W; Vyverman, W; Sime, LThe Southern Hemisphere westerly winds (SHW) are the strongest time-averaged oceanic winds. They drive the circulation of the Southern Ocean and changes in their strength and position are thought to modify the upwelling of carbon rich deep water, exerting significant control on the ocean-atmosphere balance of CO2. Thus changes in the SHW, such as the recently observed intensification, could influence whether the Southern Ocean acts as a net source or sink of atmospheric CO2, with major implications for global climate. At present the relationships between wind strength, CO2 and climate are poorly understood and there are very few studies within the core belt of the SHW in the sub-Antarctic zone c.46 to 60 deg South. We have been attempting to address this by producing centennial to decadal reconstructions of changes in SHW strength at sub-Antarctic islands in each of the major sectors of the Southern Ocean. In this talk we will show how lake sediments and peat deposits on the west coasts of these islands can yield proxy-based reconstructions of past changes in the SHW. We will review the statistical performance of our inference models, their application down selected sediment cores, and compare them with complimentary proxies of changes in wind strength based on precipitation and minerogenic inputs. The next phase of the project will use GCM simulations to help understand the patterns seen in the observational data and identify the drivers of past changes in the SHW.