Coastal Geoindicators and anomalous precipitation patterns associated with variations in the SAM and the ENSO

Resumo

TThe interaction between ocean, continent and atmosphere submits the beaches to intense sedimentary dynamics. All processes of transport, erosion and sedimentary deposition are under direct influence of the climate and its variability. This papper expound variations in geoindicators by remote sensing in three different sectors of the Rio Grande do Sul Coastal Plain during periods of precipitation anomalies (PP) associated with the Southern Annular Mode (SAM) and El Niño - Southern Oscillation (ENSO), by the MEI index. Data from the satellite TRMM were used between 1998 and 2013, correlated to the two indexes by classification matrices and t student test. Geoindicators were compared between periods of precipitation above and below average. The results show a negative correlation between PP anomalies on the central and south coast and the SAM, and a positive correlation between PP anomalies on the south coast and the MEI. No similar correlations are found between the north coast and either of the two indexes. The majority of events are PP (78%) and can be simultaneously related to a SAM+ and a MEI- or only MEI+. All PP+ events were concomitant with MEI+. The geoindicators presented observable variations by remote sensing between the below and above average rainfall periods. The greater number of PP events in the areas of the geoindicators studied may represent a lower volume of sediments transported from the backshore to the shoreline changing the sedimentary budget. Wind can transport dry sands from dune fields and fill lakes and lagoons of the study area, unbalancing the ecosystem.