Tidal Mixing Within Dease Strait in the Southern Canadian Archipelago

TidalTidal Mixing Mixing within within Dease DeaseStraitStrait in the in the southern southern Canadian Canadian Arctic Archipelago Archipelago 1 2 2 3 2 4 1 Lina M. RotermundLina M. Rotermund, W. J. Williams1, W., WilliamsK. A. Brown2, K., BrownS. L. Danielson2, S. Danielson, E. C. Carmack3, E. Carmack, B. A.2, BluhmB. Bluhm, J.4 M. Klymak 11 - -UniversityUniversity of of Victoria, Victoria, 2 2 – -FisheriesInstitute andof Ocean Oceans Sciences, Canada, 3 3- -UniversityUniversity of of Alaska Alaska Fairbanks, Fairbanks, 4 4- -UniversityUniversity of of Tromso Tromsø

Introduction LARSEN Summer tidal flow through Dease Strait at the Finlayson Islands: progression of salinity, temperature and currents. SOUND The Kitikmeot Sea in Victoria Island Taloyoak 1. Unahitak Narrows Transect the southern Canadian King Cambridge Bay William Temperature – UCTD ADCP DOLPHIN AND Island Arctic Archipelago Gjoa Haven UNION STRAIT Salinity Diagrams (CAA) is the heart of the QUEEN North West Passage. CORONATION GULF MAUD GULF Kugluktuk CHANTREY INLET Dease Strait connects Umingmaktok NE SW BATHURST Coronation Gulf & INLET Queen Maud Gulf and Bathurst Inlet narrows at the 09:00 Finlayson Islands near NE SW

Cambridge Bay. Deep Shallow 15:00 Finlayson Islands

1.

2.

3. 21:00

1. Unahitak Narrows (UN) 2. Qikirtaq Deep (QD) 3. Finlayson Islands – Queen Maud Gulf (FI – QMG)

2. Qikirtaq N S The Kitikmeot Sea is atypical in comparison to the surrounding CAA: Deep • The gulfs receive large amounts of fresh- Transect water from mainland watersheds. • Shallow-silled straits that connect the Cambridge Bay region to the CAA restrict inflow of salty Dease Strait Finlayson nutrient-rich water, hence limit new Islands primary production. • The stratification in summer between the 3. FI – QMG surface freshwater and bottom salty water 22 June 2017 Transect suppresses upward mixing of dissolved nutrients, further limiting primary production. NW SE Fast tidal flows in narrow straits can enhance vertical mixing, which should result in higher surface nutrient input and elevated biological productivity near the straits. Early spring ice-melt in many of these straits is evidence of enhanced vertical mixing bringing subsurface heat to the surface. So, we look to the narrow channels in the Kitikmeot Sea Seasonal cycle from moored instruments in Qikirtaq Deep. Pressure, Salinity, Temperature, Potential Density as possible biological hotspots within this region of low biological production. Acoustic Doppler Current Profiler Wind-driven events RV Martin Bergmann UCTD

Stratification is near zero under wintertime landfast ice. Floats

MICROCAT CTD SBE Mean summer speed 22 cm/s 6.5 m Mean winter Methods speed 9 cm/s

During the summers of 2015, 2016 and 2017, MICROCAT CTD SBE researchers aboard the Arctic Research Foundation’s RV 13 m 14 days Martin Bergmann explored the Kitikmeot Sea to determine the ecological importance of the region’s Conclusions narrow straits. Floats We observed large excursions in isopycnals over the sill of Unahitak Narrows during a tidal cycle, indicative of hydraulic jumps or topographically-induced To assess water column structure and mixing in Dease internal wave breaking. In addition, strong shear flows were measured at

Strait at the Finlayson Islands, we conducted Underway MICROCAT CTD SBE both Unahitak Narrows and Qikirtaq Deep, which may also result in vertical CTD (UCTD) and shipboard Acoustic Doppler Current 102 m mixing and drive the late spring polynya and biological hotspot. Profiler (ADCP) transects over a tidal cycle (~24 h). In The year-long mooring in Qikirtaq Deep shows tidally dominated flow in addition, seasonal variation is assessed using recently ADCP east-west direction, diurnal, semidiurnal and spring/neap tides, and wind- References recovered moored instruments, which were in-situ for a 108 m driven events during the ice-free season. Tidal current speed decreases by • Varela, D. E., D. W. Crawford, I. A. Wrohan, S. N. Wyatt, and E. C. Carmack (2013), J. Geophys. Res. Oceans, 118. half during winter months and the strong stratification of summer drops to • Dunphy, M., F. Dupont, C. G. Hannah, D. Greenberg (2005), Can. Tech. Rep. Hydrogr. Ocean Sci. 243: vi + 70 pp. year from 2016 to 2017. near zero. • Hannah, C.G., F. Dupont, A.K. Collins, M. Dunphy and D. Greenberg (2008), Can. Tech. Rep. Hydrogr. Ocean Sci. Not to scale 259: vi + 62 pp.