Do Physical Oceanographers Care About Coastal Processes in Water Less Than 20-m Deep? Andreas Münchow, College of Marine Studies, University of Delaware http://newark.cms.udel.edu/~muenchow Fort Conger, Ellesmere Island, Aug. 2003 Roger Davis 12/12/04

Questions: How does terrestial freshwater flux impact the thermohaline circulation and global climate? Do large estuarine discharges form buoyancy-driven coastal currents? How do upwelling favorable winds impact a large buoyant plume on the shelf? What are the ambient shelf currents and how do the impact the large discharge? 12/12/04

Fronts as Convergence Zones: river shelf 12/12/04

Rio de la Plata, Argentina Horizontal Stratification, large River Discharge River Plume waters Shelf Waters Surface Front Rio de la Plata, Argentina 12/12/04

Mississippi River Plume Horizontal and Vertical Stratification, Large River Discharge Plume water Shelf water Mississippi River Plume http://www.csc.noaa.gov/products/gulfmex/img/boat_1.gif 12/12/04

Mackenzie River Plume: clouds ice Note the 3 bands of different color: Sediment settling? Biogeochemistry? Pulsed discharge? Stratification? 12/12/04

Physical Oceanography: Mass is conserved density measurements Momentum* is conserved velocity measurements (*) momentum=mass*velocity 12/12/04

Mass: Hydrocast or CTD “old” style CTD (on-station) “new” style CTD (underway) 12/12/04

Velocity: Radars + Sonars Radars send and receive electromagnetic waves (radio, police) Sonars send and receives acoustic waves (sound, whales) Same physics. David Huntley with “sonar” 12/12/04

Surface drift currents (1-m) on the East Siberian Shelf Sea: From Münchow et al. (1999) 12/12/04

 East Siberian Shelf coast ice edge Sloping isopycnals suggest a flow, into the page, , or to the west coast ice edge Temperature has little effect, impact, and is generally not useful Note the correspondence of salinity and density, i.e., dynamics are dominate by an offshore source of freshwater. 12/12/04

Upwelling on a shallow shelf Temperature: Cold bottom waters surface Salinity: Fresh coastal waters move offshore Density: Stratification changes rapidly from Münchow and Chant (2000) 12/12/04

Surface currents from land-based HF radar from Münchow and Chant (2000) 25k25km Four characteristic flow patterns responding to wind and freshwater discharges Modern radars get 80k80km at the same 1-km resolution 12/12/04

Coastal Circulation off Barrow, Sept.-12, 2004 as measured by75-kHz acoustic Doppler current profiler Flow is in the opposite direction from what is the canonical view of fresh Bering Sea water entering the Arctic via Barrow Canyon 12/12/04

Conclusions Yes, physical oceanographers care about processes in shallow water Arctic oceanography community often unaware of more advanced mid-latitude coastal oceanography Physics crucial in understanding across-shore exchange processes including sediment transport Advances in modern measuring technology slow to migrate into the Arctic community 12/12/04