Marine Science 10/8/2014
Bellringer • Where do dead zones occur? • What is the definition of hypoxia?
Graphs: Check Today • Each person should have made a graph. • Here is what we should have seen.
Oxycline: What is happening to oxygen with depth?
Halocline: What is happening to salinity with depth?
Thermocline: what’s happening?
So the correct definition of thermocline, halocline, oxycline.. Cline means Change It is the depth where we see the greatest change in temperature, salinity, or oxygen respectively.
So what happened on Sept. 13?
These patterns of stratification of the water column change throughout seasons..
Why do we see changes in the water column in seasons? • Mid-latitudes, where there are noticeable differences in the weather. • The thermoclinemay not be as distinct at high latitudes (where cold most of year), or equatorial regions (where warm) • Warming of surface waters in spring= temperature layering of water. • In autumn, cooling temperatures and storms allow the water column to mix. • Distributes oxygen more evenly, temperature less dramatic fluctuations.
Density: Pycnocline • Pycnocline • Change in density with depth
What are some properties of water or water ecosystems that are of interest to scientists/the public?
Properties of Water • Polarity: water molecules have slight charges on each end due to electronegativityof Oxygen • This leads to surface tension, cohesion, adhesion, heat capacity, etc…
Properties of Water • Salinity: concentration of salts in the water, affects density • Temperature: also affects density • Dissolved Oxygen: Impacted by Temperature, Salinity, mixing/waves and other chemical properties
Salinity (s) • Also called CONDUCTIVITY, how many salt ions are dissolved in the water. (Na+, Cl-) • Measured using a REFRACTOMETER or a CTD • Units: ppt, o/oo, part per thousand • Halocline • A strong halocline indicates a stratified water column and multiple water sources • Salinity’s Impact on Density: • High salinity high density • Low salinity low density
Measuring Salinity • Refractometer vs. CTD? • CTD more accurate
Watch CTD being deployed • http://polardiscovery.whoi.edu/expedition5/video-ctd.html
Salinity and Dissolved Oxygen • Salinity Affects DO: • High salinity low DO • Low salinity high DO
How does Salinity affect DO?Which sample has more ROOM for Oxygen? Salt
Temperature (T) • Measured using a THERMOMETER • Units: Celsius, C • Thermocline: change in temperature versus depth , usually a graph • Impact on Density: • High temp low density • Low temp high density
Temperature (T) Water temperature depends on: • Currents • Latitude • Depth
Great Ocean Conveyer Belt • The great ocean conveyor belt is a constantly moving system of deep-ocean circulation driven by temperature and salinity. • Wind driven currents on surface • Thermohaline circulation • Temperature and salinity driven currents in the deep ocean
Great Ocean Conveyer Belt • Begins in the Norwegian Sea • Warm water from the Gulf Stream heats the atmosphere in the cold northern latitudes. • Water loses heat to atmosphere and becomes cold (sinks) • This process continues transporting more warm water north, and cold water south • Cold bottom water flows south of the equator all the way down to Antarctica.
Great Ocean Conveyer Belt • Cold bottom waters return to the surface through mixing and wind-driven upwelling, continuing the conveyor belt.
See Animation • http://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=3658 • Conveyer belt actually moves water very slowly (few centimeters per second) • Affects (and is affected by) weather patterns and climate
Climate Change and the Conveyer Belt
Climate Change and the Conveyer Belt • Global warming.. • Influx of warmer freshwater onto the sea surface could block the formation of sea ice, disrupting the sinking of cold, salty water. • This could slow or even stop the conveyor belt, which could result in potentially drastic temperature changes in Europe.
