Regionalisation of the discharge-sea surface temperature relationships in the Amazon basin
Josyane
Ronchail, HYBAM -Research Institute for Development (IRD)- France, josyane.ronchail@lodyc.jussieu.fr
(Presenting)
Gérard
Cochonneau, HYBAM-IRD, gerard.cochonneau@mpl.ird.fr
David
Labat, HYBAM - Paul Sabatier University -Toulouse - France, labat@lmtg.ups-tlse.fr
Luc
Bourrel, HYBAM-IRD, bourrel@lmtg.ups-tlse.fr
Laurence
Maurice-Bourgoin, HYBAM-IRD, lmaurice@unb.br
Naziano
Filizola, HYBAM-Agencia Nacional de Aguas (ANA), naziano@ana.gov.br
Jacques
Callede, HYBAM-IRD, cld@apis.com.br
Jean Loup
Guyot, HYBAM-IRD, jloup@amauta.rcp.net.pe
Eurides
Oliveira, HYBAM-ANA, eurides@ana.gov.br
Discharges in the Amazon basin are analyzed in relation to
SSTs in the equatorial Pacific and the Atlantic Oceans using
correlation, composites and wavelet techniques. Because of
the size of the basin, the main circulation patterns differ
from one region to another; thus oceanic forcing also has a
specific spatial distribution.
A stationary El Niño-low discharge / La Niña-high discharge
signal is observed in the north eastern basin, in most of the
tributaries flowing from the Guyana Shield. It disappears on
the western side of the Shield. The same signal prevails in
some regions of the southern Amazon. In the Beni River (Bolivian
Amazon) at the edge of the Andes and in the right hand
affluents of the Madeira and the downstream Tapajos and
Xingu valleys, Pacific SST anomalies account for nearly 40%
of discharge variability. The inverse signal, with low
discharge during La Niña is observed in south western Amazon,
along the Mamoré-Madeira basin. Though, this signal is not
stationary, and was only observed during the nineties.
In the southernmost Amazon basin, discharges are related to
tropical and subtropical southern Atlantic SST anomalies.
Opposite signals are noticed between the Guaporé-Mamoré-
Madeira basin on one side and the Beni River and the upstream
Xingu and Tapajos on another side. It is noteworthy that
these relationships are not stationary over the 1974-2001
period.
The long term tropical Atlantic variability is related to the
low frequency discharge variability in the north eastern
Amazon region and in Obidos that drains 80 % of the Amazon
basin.