Textbook Notes (363,264)
Canada (158,281)
Environment (154)
ENV100Y5 (125)


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University of Toronto Mississauga
Nicole Cohen

Oceans (Marine & Coastal Systems) Water density increases as salinity rises and as temperature falls. These relationships give rise to different layers of water; heavier (colder and saltier) water sinks, and lighter (warmer and less salty) water remains nearer the surface. Waters of the surface zone are heated by sunlight each day and are stirred by wind such that the proper-ties are fairly uniform throughout the zone. The salinity of surface water is influenced by a variety of interacting factors, some of which contribute to greater salinity ( e. g., evaporation and sea ice formation, both of which remove freshwater from the surface layer) and some of which contribute to reduced salinity ( e. g., precipitation, melting of sea ice, and the influx of river water, all of which bring freshwater into the surface layer). Thermocline- a zone in which temperature decreases rapidly with depth, toward the much colder deep layer (below the zone of warm, salty surface water) Salinity of the water also changes, increasing with depth along the halocline. The density of the water also changes rapidly with depth, increasing along the pycnocline. Cline- zone of rapid transition (transitional zone 18% of the ocean) 2% is surface zone and 80% is deep zone Temperature declines with depth Surface water is heated by solar energy  Colder, saltier water is denser and will sink towards to deep zone Oceans help regulate Earth’s climate because water has a very high heat capacity, which allows the water to absorb a tremendous amount of heat from the atmosphere Surface winds and heating in seawater create huge vertical flows of water, or currents. Upwelling- vertical flow of cold, deep water toward the surface occurs where horizontal currents diverge, or flow away from one another.  Often sites of high primary productivity and lucrative fisheries o Because upwelled water is rich in nutrients from the bottom  Also occur where strong winds blow away from or parallel to coast-lines Downwelling- areas where surface currents converge, or come together, surface water sinks  Transports water rich in dissolved gases, providing an influx of oxygen for deep- water life  Vertical currents also occur in the deep zone, where differences in water density can lead to rising and falling convection currents, similar to those seen in molten rock and in air Thermohaline circulation is the global oceanic circulation system of upwelling and downwelling currents.  Connects surface water flows to deeper water flows, with far- reaching effects on global climate Without or with weaker thermohaline circulation, Earth would be a very different place: The climate of France would be similar to that of Newfoundland; tropical regions would become even hotter, as their heat would not be moved north by the Gulf Stream; the deep ocean could become lifeless, lacking the oxygen- rich waters provided by the thermohaline circulation; biological productivity in the Pacific and Indian Oceans would suffer, as fewer nutrients from depth would make it to the surface layer where photosynthesis happens; and the removal of greenhouse gases from the atmosphere to the deep ocean would cease, thus accelerating global climate change. El Niño conditions are triggered when air pressure increases in the western Pacific and decreases in the eastern Pacific, causing the equatorial winds to weaken. Without these winds, the warm water that collects in the western Pacific flows eastward, suppressing upwellings along the Pacific coast of South, Central, and North America, and shutting down the delivery of nutrients that support marine life and fisheries. La Niña events are the opposite of El Niño; under these conditions, cold surface waters extend far westward in the equatorial Pacific, and weather patterns are affected in opposite ways. La Niña– influenced weather tends to be abnormally co
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