MACNBR   00242
MUSEO ARGENTINO DE CIENCIAS NATURALES "BERNARDINO RIVADAVIA"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Westerly driven vegetation and fire regime shifts at centennial timescale in southwestern Patagonia (52° S) over the last 3000 years
Autor/es:
MORENO P.I.; VILANOVA I; VILLA MARTÍNEZ R.P
Lugar:
Dunedin
Reunión:
Congreso; VII Southern Connection Congress; 2013
Institución organizadora:
University of Otago
Resumen:
Twentieth century
instrumental records reveal a persistent southward displacement and intensification
of the Southern Westerly Winds (SWW) contemporaneous with steady increases in
atmospheric temperatures and CO2 concentrations, glacial recession at a global
scale, and a positive phase of the Southern Annular Mode (SAM). To date it is
unclear whether this mid-latitude atmospheric phenomenon represents natural
variability or a response to human-induced climate perturbations. Here we
present a paleovegetation and paleofire record from Lago Cipreses (51° S),
southwestern Patagonia, that reveals periodic ~ 200-yr long droughts since 3000 cal
yr BP. The most recent of these events started in the 19th century
and has persisted until the present, concomitant with positive anomalies of the
SAM and widespread disturbance of the southwestern Patagonian environments by
Euro-Chilean settlers. We identify nearly identical shifts during the Late
Bronze Age, Roman and Medieval Warm Periods, and between 1600-1400 cal yr BP,
which we attribute to positive anomalies of SAM. These alternate with humid
phases which coincide in timing with the Iron Age and Dark Ages cold periods,
and the Little Ice Age. We propose that
the SWW varied in concert with important temperature anomalies in the Northern
Hemisphere over the last 3000 years, with positive SAM-like changes
corresponding with warm episodes, and vice versa, and conclude that the current
poleward shift and intensification of the SWW reflects juxtaposition of natural
and human-induced variability since the 19th century, prviding a
potential source of future climate variability through alternations of the
ocean-atmomsphere exchange of CO2 at high southern latitudes.