Remote sensing the dynamics of suspended particles in the Mackenzie River plume (Canadian Arctic Ocean)

Abstract

Climate change significantly impacts Arctic shelf regions in terms of air temperature, ultraviolet radiation, melting of sea ice, precipitation, thawing of permafrost and coastal erosion. A direct consequence is an increase in Arctic river discharge with an expecta- tion of increased delivery of organic carbon sequestered in high-latitute soils since the 5 last glacial maximum. Monitoring the fluxes and fate of this terrigenous organic carbon is problematic in such sparsely populated regions unless remote sensing techniques can be developed to an operational stage. The main objective of this study is to develop an ocean colour algorithm to oper- ationally monitor dynamics of suspended particulate matter (SPM) on the Mackenzie 10 River continental shelf (Canadian Arctic Ocean) using satellite imagery. The water op- tical properties are documented across the study area and related to concentrations of SPM and particulate organic carbon (POC). Robust SPM and POC:SPM proxies are identified, such as the light backscattering and attenuation coe ffi cients, and relation- ships are established between these optical and biogeochemical parameters. Follow- 15 ing a semi-analytical approach, a regional SPM quantification relationship is obtained for the inversion of the water reflectance signal into SPM concentration. This relation- ship is validated based on independent field optical measurements. It is successfully applied to a selection of MODIS satellite data which allow estimating fluxes at the river mouth and monitoring the extension and dynamics of the Mackenzie River surface 20 plume in 2009, 2010 and 2011. Good agreement is obtained with field observations representative of the whole water column in the river delta zone within which terrige- nous SPM is mainly constrained (out of short periods of maximum river outflow). Most of the seaward export of SPM is observed to occur within the west side of the river mouth. 25 Future work require the validation of the developed SPM regional algorithm based on match-ups with field measurements, then the routine application to ocean colour satellite data in order to better estimate the fluxes and fate of SPM and POC delivered by the Mackenzie River to the Arctic Ocean.