1. Flow estimates through the Canadian Archipelago from synoptic ADCP surveys
Andreas Münchow
University of Delaware
Kelly Falkner
Oregon State University
Humfrey Melling
Institute of Ocean Sciences
1/17/2019

2. Objectives: Freshwater fluxes from tidal to interannual time scales:
Quantify flows
Quantify tracer distributions
Diagnose dynamics
Suggest monitoring array
Barotropic vs. baroclinic contribution to flux?
Local vs. remotely forced flux?
Tidally rectified contribution to mean flux?
1/17/2019

3. Methods: 5-year project 2003-2007
Moorings (velocity, pressure, salinity, ice draft, tracers/water samplers)
Surveys (velocity, hydrography, tracers)
Remote Sensing (AMSR*, AVHRR)
Paleo-environmental proxies (bivalves)
Modeling (sub-mesoscale winds)
Mooring deployment
Kennedy Channel, August 2003
~40 year’s worth of “tree rings”
5-year project
(*) Advanced Microwave Scanning Radiometer:
89 GHz, daily coverage, 4x6 km spatial resolution
1/17/2019

4. Challenges: Magnetic North Pole nearby Ice Bridges and ice-bergs
Strait of Gibraltar
Challenges:
Magnetic North Pole nearby
Ice Bridges and ice-bergs
Strong tidal currents (~ 1 m/s?)
small internal Rossby radii (ocean and atmosphere)
Ageostrophic winds (hydraulics, katabatics)
Ice and water contribute to freshwater flux
Nares Strait
Ellesmere
Island
Greenland
1/17/2019

5. ADCP Velocity Aug. 2003 Measured Detided = Measured-Tides Ellesmere
Island
The narrow jet off
Ellesmere Island
opposes the local winds.
Detided =
Measured-Tides
1/17/2019

6. Winds Aug. 2003: Along 2003 ship track in Nares Strait Ellesmere
Greenland
Ellesmere
Island
Winds
Aug. 2003:
Along 2003 ship track in Nares Strait
Winds during our survey and mooring work in Nares Strait were generally from the south and opposed the generally southward flow.
1/17/2019

7. Barotropic tidal currents from 5-km OSU model (prior talk):
Robeson
Channel
Smith
Sound
~15 cm/s but variable
Largely uniform
1/17/2019

8. Semi-diurnal tidal currents from ADCP survey in Robeson Channel
Major axis
current
Current
phase
orientation
Minor/major
axis current
USCGC Healy ADCP:
75 kHz phased-array
0.5 Hz
Military grade p-code GPS
Ashtech differential attitude GPS
15-m vertical bins
First bin ~25-m below surface
Range ~300-m to 600-m
1/17/2019

9. ADCP Velocity Aug. 2003 Measured Detided = Measured-Tides Ellesmere
Island
note the narrow jet
off Ellesmere Island
Detided =
Measured-Tides
1/17/2019

10.  ~0.2±0.1 Sv Velocity Aug. 2003: against the wind  Wind
Across-channel
~0.2±0.1 Sv
against the wind
Along-channel
Ellesmere
Greenland
1/17/2019

11.  Hydrography Robeson Channel Aug. 2003  Wind Density Northward wind
Southward flow
Temperature
Salinity
1/17/2019

12. tidal constituents estimated and removed
Two ADCP surveys of
Smith Sound area on
Aug.-3 and Aug :
3-min averaged
depth-averaged
Tidally biased flow
As above, but with three
tidal constituents estimated
and removed
1/17/2019

13. Smith Sound detiding with 2 semi-diurnal and
1 diurnal constituents (depth-averaged currents)
North (cm/s)
East (cm/s)
Survey Aug.-3
Survey Aug.-14
Time (days)
1/17/2019

14. Conclusions
Freshwater flows scale with internal deformation radius L~5-km both Robeson Channel and Smith Sound
Prior volume flux estimates through Nares Strait potentially biased as L is generally not resolved
Tidal current estimation need improvements
Spring view across
Nares Strait
from Greenland
1/17/2019