Statistical associations of basin streamflow on sea surface salinity variability across major global deltas.

Sea surface salinity ( ) is a key parameter for the thermohaline circulation of global oceans, as well as the global hydrologic cycle. Near the deltas, inland streamflow through large catchments plays a crucial role in mediating salinity, which is vital for maintaining an agro-hydrological balance in the deltas. With recent remote sensing data sources providing both   and streamflow at global scales, we calculated the statistical associations of   with simulated basin streamflow ( ) at a monthly scale in 48 major deltas across the globe. The monthly   data was downloaded globally at   intervals from the SMAP RSS L3 products. The hourly streamflow data was extracted from HYMAP streamflow routing simulations (available at   spatial grids) within NASA’s LIS modeling framework. The streamflow data was spatiotemporally aggregated before performing the statistical analyses. We calculated the associations over different monthly-lags and plume distances and obtained the optimal correlations. The optimal correlation coefficients ( ) reveal strong anticorrelation phenomenon between   and   (  for seasonal data at 28 deltas, and   for de-seasoned data at 21 deltas). In addition to basin streamflow, we considered a number of sea surface climate forcings (precipitation, sea surface temperature, and wind speed) to perform similar statistical comparisons with  . The results revealed that   near the deltas are more influenced by basin streamflow in general. From a physical science perspective, we found consistent outcomes in the majority of deltas, with some irregularities in deltas with strong anthropogenic and management influences (e.g., deltas containing low forest cover and high reservoir areas). The anticorrelation phenomenon was more prominent in large deltas, specifically located near the tropical climates, which experience high streamflow and no ice-melting. We also found that the anticorrelations are more profound in river dominated deltas (e.g., deltas where the fluvial dominance ratio is greater than 1). The findings of this research will be useful for delta researchers aiming to devise global scale strategies amidst the rising threats of salinity intrusion.