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

Abstract

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.

Late Holocene intensification of the westerly winds at the subantarctic Auckland Islands (51° S), New Zealand

“…9). In addition, a pollen record from the Falkland Islands (52 • S, 58 • W) indicates intensified winds from 2000 to 1000 yr BP (Turney et al, 2016a Schimpf et al, 2011) indicates increased wind-derived precipitation from 1500 to 800 yr BP, and decreased precipitation from 800 to 500 yr BP (Fig. 9), consistent with our record from the Auckland Islands.…”

“…Palaeoclimate records of wind strength reconstruct changes in atmospheric circulation using the strong positive correlation between wind strength and precipitation in the middle latitudes of the Southern Hemisphere (Garreaud, 2007). Although there are a number of records from southern New Zealand (Gellatly et al, 1988;Knudson et al, 2011;Lorrey et al, 2008Lorrey et al, , 2014Putnam et al, 2010;Turney et al, 2017), Tasmania (Saunders et al, 2012), and southern South America (Aracena et al, 2015;Ariztegui et al, 2010;Lamy et al, 2001Lamy et al, , 2010Moreno et al, 2009Moreno et al, , 2014Moy et al, 2008Moy et al, , 2009Schmipf et al, 2011;Turney et al, 2016a;Waldmann et al, 2010;and others), there are fewer from the subantarctic islands, all of which have a palaeovegetation focus (McFadgen and Yaldwyn, 1984;McGlone 2002;McGlone et al, 2000McGlone et al, , 2010McGlone and Moar, 1997;Turney et al, 2016b).…”

Solar Output Controls Periodicity in Lake Productivity and Wetness at Southernmost South America

“…The authors noted the common structure of centennial changes in SAM with paleoclimate records from the NH, and an in-phase interhemispheric coupling thought atmospheric teleconnections15. Similar, a recent study of enhanced westerly intensity during the last 2,600 years at the Falkland Islands (Patagonia Atlantic coast) show the same periodicity, coherent with radiocarbon production rates, suggesting that solar forcing plays a dominant role in modulating the strength of the SWW16. Moreover, a short (1,500 years) but high-resolution speleothem record from south-central Brazil showed the sensitivity of the SAMS to solar forcing with a cyclicity of 208 years.…”

The Antarctic Centennial Oscillation: A Natural Paleoclimate Cycle in the Southern Hemisphere That Influences Global Temperature

“…Similarly, westerly wind records in the SH (Falkland Islands) for the past 2600 years as assessed from records of pollen distribution show discernible AAO spectral peaks at 242, 185, 150 and 95 years that average 168 years [72] (Figure 5a, p. 194), similar to the 193-year discernible peak in the Holocene spectral periodogram of the ACO (Figure 3) and the 162-year average period over the last 2,600 years ( Figure 1d). We therefore conclude, subject to confirmatory research, that the ACO is the probable paleoclimate precursor of, and is continued into the present by, the contemporary Antarctic Oscillation (AAO/SAM/SOI).…”