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 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.

Solar irradiance and primary productivity controlled mercury accumulation in sediments of a remote lake in the Southern Hemisphere during the past 4000 years

“…This indicates that productivity in LH followed these short term changes in irradiance (P erez-Rodr ıguez et al 2016). Similar periodicity in past climatic changes in Patagonia has been observed in other studies (Turney et al 2016).…”

17,000 years of vegetation, fire and climate change in the eastern foothills of the Andes (lat. 44°S)

“…Asynchronous forest expansions may been noted in pollen data from the Falkland Islands, where variability in westerly intensity has been ascribed to oscillations in solar irradiance, namely the effects of the de Vries/Suess solar cycle (Turney et al 2016). Although our data lack the temporal resolution to register these highfrequency changes, our results show peaks in tree abundance throughout the eastern flanks of the Andes at ca.…”

“…Ocean (Moy et al, 2002) and with high solar irradiance (Turney et al, 2016). A tree-ring reconstruction from Tasmania (Cook et al, 1999) suggests that, in the southern hemisphere, higher solar output at the time led to increased summer temperatures (Lüdecket et al, 2015).…”

Intensification of Southern Hemisphere westerly winds 2000–1000 years ago: evidence from the subantarctic Campbell and Auckland Islands (52–50°S)

“…The timing of the hiatus in upper tree growth is observed in other sectors of the Southern Ocean that are highly sensitive to changes in westerly airflow. The absence of Dracophyllum wood at (Turney et al, 2015), biogenic carbonate accumulation rate (AR) from Palm2, Chile (53˚S) (stars denote volcanic ash horizons, triangles 14 C ages) (Lamy et al, 2010) (C) and sea surface temperature (SST) from ODP-1098 (65˚S, Palmer Deep), west Antarctic Peninsula (Shevenell et al, 2011) (D). elevation is synchronous with the enhanced delivery of South American (exotic) pollen and microcharcoal to the Falkland Islands, interpreted to represent stronger winds between 2 and 1 ka (Fig.…”

“…peats and trees) on subantarctic islands offer the potential to generate high-resolution records of changes in subpolar westerly airflow across the Southern Ocean. Recent work from Canopus Hill on the Falkland Islands in the South Atlantic (52˚S) (Turney et al, 2015) suggests a phase of enhanced flow between 1.8 and 1.0 ka based on the aerial transportation of exotic pollen and microcharcoal particles (<106 mm) from South America, providing direct evidence of stronger winds at this latitude across this period. Other workers, however, have suggested the last 5 ka was characterized by asymmetrical flow across the hemisphere (Fletcher and Moreno, 2012), which would imply the enhanced flow identified on the Falklands was only of regional significance.…”