Coastal Oceanography Outline Global coastal ocean Dynamics Western boundary current systems Eastern boundary current systems Polar ocean boundaries Semi-enclosed seas and islands

What is the coastal ocean? The coastal ocean is the portion of the global ocean where physical, biological and biogeochemical processes are directly affected by land It is either defined as the part of the global ocean covering the continental shelf or the continental margin

Importance Represent 20% of Earth surface 50% of human population lives in coastal regions By 2025 projected that 75% of human population will live in coastal areas Support most fisheries, sink/source for CO2, sites of water formation, sites for resource extraction

Coastal Ocean Shelf seas – depths of 10s to 100s meters, extend outwards from coast to shelf break (10s to 100s km) Beyond shelf break have slope sea – extend outwards to deep ocean depths Extend along coastlines from poles across equator – affected by the full range of climate variability Experience remote and local forcings – mixture of dynamics – makes study challenging

Salinity increases towards shelf break Winter – vertically homogeneous Summer – two layer stratified system Coastal ocean structure off NJ

Across-shelf salt transport Middle Atlantic Bight Offshore increase in salinity – freshening from river discharge inshore Density barrier (front) at shelf break separates fresher shelf water from salty ocean water Salt mixes across front

Dynamics Connectivity to adjacent deep ocean Tides – mixing and hydrographic structure – Gulf of Maine, Amazon and Patagonian shelves Fresh water – Land runoff, advection by ocean currents, sea ice, excess precipitation (tropics, monsoons) – Affects stratification, buoyancy forced baroclinic flows Wind stress Surface heat fluxes – Water formation regions, seasonal heating/cooling Sea ice – Air-sea interactions, convective mixing, stratification Coriolis effects, Ekman flow, coastal upwelling

River Plumes Discharge of freshwater onto shelf turns right due to Coriolis and mixes Hudson River Plume

St. Laurence River adds freshwater in Canada Coriolis turns freshwater southward Other rivers add freshwater – turn southward Buoyancy drives southward flow on Middle Atlantic Bight shelf Effect of Freshwater

Secondary Wind Effects – Upwelling winds Push shelf flow offshore

Columbia River – West coast of US Produces a large plume Direction of turning on shelf is variable

Flow Instability Ocean flow is sufficiently energetic that it becomes unstable West coast upwelling create eddies

Cold Pool – result of winter deep mixing Cold water is isolated by summer stratification Deep shelf water remains cool throughout summer Provides habitat for cold adapted infauna – clams

Change in cold pool

Brink and Robinson, The Sea, 2005 Coastal Ocean – global distribution

Panregional Categories Western boundary current systems Eastern boundary current systems Polar ocean boundaries Semi-enclosed seas and islands

Western Ocean Boundary Shelves Influenced by western boundary currents Advective dominance Shelf impacted by eddies and rings Intrusions of deep ocean water masses

Warm core rings Form from instabilities in flow Occur where GS separates from shelf Mechanism for flushing shelf waters

South Atlantic Bight Gulf Stream at the outer shelf edge Gulf Stream Filaments and Eddies

Gulf Stream puts water at shelf edge Upwelling moves water onto the shelf GS Front

Eastern Ocean Boundary Shelves Influenced by eastern boundary currents Upwelling regions Wind-driven

Eastern Boundary Current Upwelling

California Current Filaments and Jets

Stratification retention frontal exchanges Sea ice Ice shelves Modify dynamics Polar Shelves - Western Antarctic Peninsula continental shelf

ACC CDW

Antarctic Circumpolar Current

Ross Sea continental shelf

Past 50 years Projected next century Smith et al. (2012, Oceanogr.)

Arctic Rivers

Next Class Interdisciplinary physical oceanography applications, international global environmental change research