Ice and Permafrost Effects on Delta Morphology and Channel Dynamics
Arctic regions are changing rapidly as temperatures warm, and these changes directly affect Arctic river deltas that connect the continents to the Arctic Ocean. Because of the difficulty of field-based research in these remote regions, we do not yet understand how ice cover and frozen soil (i.e., permafrost) affect coastal change, which limits our ability to predict coastal dynamics in a warming environment. A study by researchers at Los Alamos National Laboratory used a numerical model to examine the impacts of ice cover and permafrost on Arctic deltas. Scientists found that both ice and permafrost make channels more stable and increase the delivery of sand and mud to the coastal ocean. Ice cover, especially, encourages flooding on the delta that should help coastal landscapes keep pace with sea level rise.
Little research exists on the effects of ice and permafrost on large-scale long-term delta dynamics, despite the fact that deltas are critically important in connecting rivers to the ocean and significantly modify the delivery of riverine material to the coastal ocean. This study addresses this knowledge gap by examining the long-term evolution of Arctic deltas and provides insights on future Arctic coastal dynamics as permafrost thaws and sea ice retreats.
Arctic regions are warming rapidly, causing frozen soils to thaw and sea ice to melt. These changes directly affect Arctic river deltas that connect the continents to the Arctic Ocean. Because of the difficulty of research in these remote regions, we do not yet understand how ice cover and frozen soil (i.e., permafrost) affect coastal change, which limits our ability to predict coastal dynamics in a warming environment. This study uses a numerical model to examine the impacts of ice cover and permafrost on Arctic delta dynamics. We found that both ice and permafrost make channels more stable. Ice fills channels and forces flow underneath the ice, preserving channels that would otherwise be filled with sediment over time. This also causes increased delivery of sand and mud to the coastal ocean. Ice cover enhances vertical delta growth by encouraging flooding, implying that a reduction in ice cover resulting from warming will result in less vertical delta growth and therefore less of an ability to keep up with sea-level rise. Our results also suggest that loss of permafrost and ice may result in more mobile channels, which will fundamentally change how rivers deliver water, sediments, and nutrients to the coastal ocean.