Answer to Question 1
Ocean current measurements consist of measurements of velocity and direction and velocity for surface and subsurface current flow. Both surface and subsurface currents can be measured directly or indirectly. Direct methods of ocean currents are floating devices that are can be tracked over time or fixed devices. Indirect methods consist of determining the internal distribution of water density and the corresponding pressure gradient, radar/satellite altimeters to produce dynamic topography maps, and Doppler flow meters to determine subsurface water movement.
Answer to Question 2
There is a rapid change in salinity between the depths of about 300 meters (980 feet) and 1000 meters (3300 feet). For the low-latitudes, the change is a decrease in salinity, because surface water salinity is high due to evaporation and little to no precipitation and runoff. For the high-latitudes, the change is an increase in salinity because surface water salinity is low due to abundant precipitation and runoff and the melting of freshwater icebergs. In addition, cool temperatures limit the amount of evaporation that takes place.
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