Coronavirus Information for the UC San Diego Community

Our leaders are working closely with federal and state officials to ensure your ongoing safety at the university. Stay up to date with the latest developments. Learn more.

Observations of shelf exchange and high-frequency variability in an Alaskan fjord

TitleObservations of shelf exchange and high-frequency variability in an Alaskan fjord
Publication TypeJournal Article
Year of Publication2018
AuthorsMerrifield S., Otero M, Terrill E
JournalJournal of Geophysical Research-Oceans
Volume123
Pagination4720-4734
Date Published2018/07
Type of ArticleArticle
ISBN Number2169-9275
Accession NumberWOS:000441888200017
Keywordsbasin; climate; driven; fluctuations; greenland; internal waves; oceanography; pacific; salmon production; stratified flow; water
Abstract

High-frequency observations collected over 3 years are used to describe upper-ocean variability in Behm Canal, a nonglacial fjord in Southeast Alaska. The fjord is sheltered by surrounding topography and connected to the outer continental shelf by a 400-m-deep strait. Summer conditions are characterized by strong near-surface stratification, a sea breeze wind regime, and tidally dominated flows. In nonsummer months, baroclinic subinertial flows exceeding 0.5 m/s dominate the velocity record. The flow events represent a wind-driven response to low-pressure systems that impact the coast as they propagate across the Gulf of Alaska. The observations suggest that the storm systems generate downwelling events that propagate into the fjord with a mode-one-like vertical structure in the upper 60 m. Following the initial up-fjord current pulse lasting approximately a day, a down-fjord flow occurs lasting several days, the duration of the downwelling anomaly. These subinertial downwelling events likely are the dominant mechanism of shelf-fjord exchange, with estimated fjord-flushing times of 50 days. The downwelling events are accompanied by enhanced near-inertial shear, which exhibits downward energy propagation. Evidence for enhanced energy near the maximum buoyancy frequency in the thermocline suggests high-frequency internal wave trapping, with the primary energy source in the semidiurnal band associated with tidal and wind forcing. The observations highlight the importance of shelf-fjord coupling through meteorological forcing and the existence of internal wave energy at a range of frequencies, which have implications for mixing and transport within the fjord.

DOI10.1029/2018jc013931
Short TitleJ Geophys Res-Oceans
Student Publication: 
No