Seafloor temperature and conductivity data from Stefansson Sound, Alaska

Abstract

Overconsolidated sediments, seasonal seafloor freezing, and ice-bonded permafrost are unique features in shallow arctic coastal waters. They are related to low seawater temperatures and varying salinities. Seabed temperatures can be less than −1.0°C for much of the year, with noticeable warming occurring only during the summer months. Observations from recent deployment of three instruments in Stefansson Sound and data from an earlier deployment, which included sites in Harrison Bay, showed decreasing mean annual seafloor temperatures with increasing water depth, ranging from −0.9°C in 4.4 m of water to −1.6°C in 14 m of water. Salinities also varied seasonally, with noticeable freshening developing during the summer and highly uniform values occurring during the winter. Periodic temperature and salinity measurements at sites in Stefansson Sound, made during August 1987 and August 1989, also helped verify the data obtained with the seabottom instruments. Seasonal freezing of the seabed can begin in late September and may noticeably change its engineering properties. In areas of coarse-grained sediments, ice bonding and strengthening of the seabed can result. In areas of fine-grained sediments it appears that seasonal freezing of the seafloor can cause overconsolidation of the seabed sediments. This densification process can result in a significant permanent increase in strength.