Abstract
The Arctic is directly impacted by climate change. The increase in air temperature drives the thawing of permafrost and an increase in coastal erosion and river discharge. This leads to a greater input of sediment and organic matter into coastal waters, which substantially impacts the ecosystems, the subsistence economy of the local population, and the climate because of the transformation of organic matter into greenhouse gases. Yet, the patterns of sediment dispersal in the nearshore zone are not well known, because ships do not often reach shallow waters and satellite remote sensing is traditionally focused on less dynamic environments. The goal of this study is to use the extensive Landsat archive to investigate sediment dispersal patterns specifically on an exemplary Arctic nearshore environment, where field measurements are often scarce. Multiple Landsat scenes were combined to calculate means of sediment dispersal and sea surface temperature under changing seasonal wind conditions in the nearshore zone of Herschel Island Qikiqtaruk in the western Canadian Arctic since 1982. We use observations in the Landsat red and thermal wavebands, as well as a recently published water turbidity algorithm to relate archive wind data to turbidity and sea surface temperature. We map the spatial patterns of turbidity and water temperature at high spatial resolution in order to resolve transport pathways of water and sediment at the water surface. Our results show that these pathways are clearly related to the prevailing wind conditions, being ESE and NW. During easterly wind conditions, both turbidity and water temperature are significantly higher in the nearshore area. The extent of the Mackenzie River plume and coastal erosion are the main explanatory variables for sediment dispersal and sea surface temperature distributions in the study area. During northwesterly wind conditions, the influence of the Mackenzie River plume is negligible. Our results highlight the potential of high spatial resolution Landsat imagery to detect small-scale hydrodynamic processes, but also show the need to specifically tune optical models for Arctic nearshore environments.
Highlights
Climate change is stronger in the Arctic than anywhere else on Earth [1]
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We show that even the older Landsat sensors (TM, ETM+) are powerful tools for ocean color applications and allow the investigation of Arctic nearshore environments by providing high spatial resolution optical imagery spanning over nearly 35 years
Summary
Climate change is stronger in the Arctic than anywhere else on Earth [1]. It leads to multiple impacts on the biophysical system, including intensified permafrost thaw, increasing river discharge and stronger coastal erosion. Because of enhanced coastal erosion and increased discharge from rivers, sedimentary inputs to the Arctic nearshore zone and shelf areas rose remarkably in the second half of the 20th century [6–8]. Arctic coasts are actively eroding leading to an enhanced input of sediment [11]. The mean annual rate of shoreline erosion of Arctic coasts is 0.5 m/a [12]. Higher values up to 10 m/a occur at coasts with high ice content, near deltas of large rivers entering the Arctic Ocean (Mackenzie, Lena, Yenisei, Ob, Kolyma) [12]
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