Recapping of Smith et. al
How did the authors interpret this general distribution (Fig 2B) in the context of the Major Current Systems. How does anb unintentional tracer release expierment help scientists study currents and ocean circulation. What drives gyre circulation?
The figure 2B showcases the site in which the expierment looks at the 137 Cs tracer as it is transported in the the North Pacific Gyre. In this study, we saw that the Kuroshipo current transported the plume from Fukushima Northward until it was then transported to the eastern Pacific via the Northern Pacific Current (NPC). From there it traveled east until it came upon a bifucation zone, where the ocean currents diverged into the poleward Alaska Current and the equatorial flowing California Current. The figure highlights this bifuication point of the tracer transport. What the researchers abserved is that the eastern flow of the NCP showed higher concentrations of the 137Cs tracer, and had conditions that promoted surface water mixing, but as water moved more towards the coast the concentration of 137Cs tracer drops off signifigantly and surface water mixing comes to a minimum. Overall it is a picture of the gradient of the relationship between tracer [137Cs] and surface water mixing. Expierments like these are important for scientist to look at the reality of net transport in grye circulation, and the relationship transport might have with downwelling, upwelling, and seasonal variation. The true fruit of collecting this raw data is to be able to calibrate models so that their outputs can be refined boosting reliability in forcasting, prediction modeling, and refine the growing field of using machine learning modles to locate patterns in these data sets.
Ultimately what drives gyre circulation is a few things: atmospheric pressure systems, wind, friciton, and the Earth's roation. The Earth's atmospheric pressure systems are mostly relevant to variables concerning the wind. High pressure systems exist near the equator and Low pressure systems exist near the poles. These pressure systems ultimately dictate the strength, direction and length of these winds. Then the winds push against the sufrace waters moving them in the direction they push. The fricitonal forces make it so the surface current drags the subsequence currents beneath it along with it. However, this is not so striaght foward. Both the wind and the currents are impacted by the rotation of the earth creating what is known as the Coriolis Effect. The Coriolis Effect refacts the winds that move the water at that refacted direction but then the currents themselves are subjected to that same effect creating additional refraction. This makes it that surface currents are transported 45 degrees from wind direction and subsequent currents are refracted around 90 degrees. This is whats known as the Ekman Spiral. This spiraling happens at all points in which strong winds move the surface waters, creating a seires of currents that refract in such a way that (in the Norther hemisphere) move in a clock wise fasion. This happens reversly in the Southern Hemisphere.