Abstract
AbstractWe analyze 10 years of Gravity Recovery and Climate Experiment (GRACE) terrestrial water storage anomalies (TWSAs) over tropical South America along with seven climate indices linked to equatorial Pacific and tropical Atlantic oceans sea surface temperatures (SSTs) using a multichannel singular spectrum analysis and lagged cross correlations. We focus on the interannual, nonlinear modes of covariability between TWSAs and SSTs. By comparing the relative distributions of the leading modes, we identify teleconnections between TWSAs, Pacific and Atlantic SSTs at different time periods. Thus, the northern and northeastern regions of tropical South America are mainly influenced by Pacific SSTs, while the central and western Amazon regions are more influenced by Atlantic SSTs. The former regions are more sensitive to central Pacific SSTs than to eastern Pacific SSTs. A quasi‐biennial mode explains the largest part (27%) of the residual, interannual cross covariance and is found both in the El Niño–Southern Oscillation and in the Atlantic meridional mode. A trend‐like mode explains the second largest part (24%) of the residual cross covariance and may be caused by the following: (1) the decadal variability in the North Pacific climate, as expressed by the negative trend in the Pacific decadal oscillation and by increased water storage in northern and northeastern South America, (2) the melting of Andean glaciers in Peru and Bolivia due to man‐induced increase in land surface temperatures, and (3) the land use/cover changes after deforestation leading to increased runoff and groundwater recharge, expressed by increased water storage in southern Amazon regions.
Highlights
A 6–7 month lag was found between El Niño–Southern Oscillation (ENSO) and discharge at Manacapuru and Obidos [Richey et al, 1989; Zeng 1999], while Zeng [1999] found
A 1–2 month lag between rainfall and basin-averaged soil moisture in the Amazon. These results are consistent with the 4–6 (i.e., 6–7 minus 1–2) month lag we find between terrestrial water storage anomalies (TWSAs) and SOI in the lower Amazon
In the Magdalena basin, no lag is found between TWS, SOI, and discharge [Restrepo and Kjerfve, 2000], which is consistent with the very small lags found between Gravity Recovery and Climate Experiment (GRACE)-TWSAs and SOI there (Figure 9)
Summary
One of the goals of this study is to highlight this influence. One of the objectives of this study is to determine whether or not GRACE TWSAs are sensitive to the different ENSO types. By using climate indices as MSSA channels in addition to the GRACETWSAs, we aim to extract the part of each climate index variability that is correlated to the GRACE-TWSAs, to highlight possible teleconnections between SSTs and TWSAs at different time scales
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