633 / 2024-09-18 17:51:10

Recent (last 25 years) evolution of particulate river discharge into the ocean in temperate and Arctic regions based on field and satellite observations. Impacts of climate change effects and human activities.

satellite observations,river discharge,plume dynamics

The discharge of terrestrial substances into the ocean plays a key role in land to sea fluxes, heath of coastal ecosystems and burial of organic matter in continental shelves. Effects of climate change and human activities on river discharges and their impacts on coastal waters must be carefully monitored, notably in temperate regions (where river discharges are expected to decrease but associated to more extreme events such as storms, heat waves and peak floods) and in the Arctic Ocean (impacted by reduced sea ice, permafrost thaw, enhanced rainfall and dam constructions).

In this study, 25 years of field (e.g., hydrologic stations) and satellite (ocean color and thermal infrared) observations are combined to document and understand the recent evolution of river liquid and solid discharges and their impacts on adjacent coastal waters directly affected by river plumes. Considering seasonal to inter-annual time scales, a detailed reconstruction of river discharge and river plume dynamics is provided in order to highlight temporal trends. Relationships are established between the observed plume dynamics and changing key physical forcings such as river discharge, erosion in river basins, tides and wind effects but also dam constructions.



In temperate regions, there is no significant temporal trend detected but results clearly highlight how the river liquid and solid discharges control the extent and dynamics of river plumes (e.g., Constantin et al. 2018). Rather unexpected results are obtained in the Arctic region where river discharges to the ocean are predicted to rise due to climate change effects (e.g., Doxaran et al. 2015). The discharge of the major Siberian rivers actually significantly decreased over the last 25 years, mainly due to human activities (dam constructions). The discharge of the major North-American rivers only very recently increased, highlighting a strong inertia to climate change effects (Tarasenko et al. 2023). The direct impacts of river discharges into coastal waters are clearly revealed by satellite observations which also allow studying the recent melting of glaciers and associated turbid plumes.