Biogeochemistry of suspended particulate matter and sediment from the nearshore zone of Herschel Island, Canada

Collapse of permafrost coasts delivers large quantities of particulate organic carbon (POC) to arctic coastal areas. The objective of this study is to assess the pathways and fate of POC derived from thawing and eroding permafrost coasts in the nearshore zone, to better understand its impact on the carbon cycle and climate. We collected suspended particulate matter and sediment samples at the coastline and in the nearshore zone of Herschel Island - Qikiqtaruk (N 69.60°; W 139.00°) during a two‐week period in July‐August 2017. Locations were labelled A - H clockwise around the island, starting at the NE corner (Collinson Head). Samples were taken in transects perpendicular to the coast, at point locations offshore ('Monitoring point 1 - 3'), and from 'thaw streams', creeks carrying material from retrogressive thaw slumps and other abrupt thaw features, at various locations around the island. A total of 49 locations were visited; 12 at thaw streams, and 37 in the nearshore zone ranging from right at the shoreline to up to 20 m water depth (about 2 km offshore). We performed biogeochemical analyses (CN, δ13C, Δ14C) and sedimentological analyses (grain size, mineral surface area) in order to trace the pathway of permafrost material from its source to the nearshore water column and sediments.