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Kuroshio Current - contribution draft
Western boundary currents (WBC's) are integrated parts in the world's climatic balance. The Kuroshio Current is the western boundary current of the northern Pacific Ocean, influencing regional climate and weather patterns mainly through the input of warm waters from lower latitudes northward into the western edge of the Pacific. Along with the other WBCs in the Pacific, the Kuroshio Current is subject to seasonal changes that manifest in different flow rates, bifurcation latitudes, water salinities, and more. Circulation within the Pacific Ocean is largely influenced by this transport of warm salty water north along the Western boundary providing structure to the western edge of the North Pacific Gyre. The resulting heat fluxes in this area represent some of the largest heat exchanges from ocean to atmosphere within the entire Pacific Basin, being more pronounced during the winter season. This effect supports unstable atmospheric conditions, causing monsoonal rain events through the summertime and strengthening typhoon storms as they pass over the current. The climate of many Asian countries has been affected by these processes for millions of years.

Climate Implications
As the Kuroshio Current separates from the equatorial current and flows northward, warm water from the Western Pacific Warm Pool is input into the north west Pacific Ocean Basin. Much of the heat flux occurs via the Kuroshio Extension, which splits off from the Kuroshio Current typically somewhere along the coast of Japan. The process of warm water injection into the open ocean plays an important role in the formation of North Pacific Subtropical Mode waters and the regulation of sea surface temperatures, affecting moisture transport across the western Pacific Basin. North Pacific Subtropical Mode Waters are created when Kuroshio Extension waters lose large amounts of heat, moisture, and salt to the cold dry northerly winds during boreal wintertime months, creating dense surface waters and deep ocean convection. Atmospheric heat flux processes in this area create feedbacks that enhance water temperature contrasts and can cause SST features to last well past the end of the boreal winter. For example, with residual cooled surface waters in the spring and summer months, warm moist air from the south can cause low cloud formation and reflection of solar radiation, extending SST cooling. Typically the resulting homogenous water mass separates the seasonal pycnocline from the surface waters in the mid to late summer months, being stratified below the warmer surface waters until being brought back to the surface with the shoaling of the mixed layer in winter. The contrast in water temperatures is stark, and the lateral advection of this water mass can be traced for thousands of kilometers. Mode water formation is variable and largely dependent on the flow intensity of the Kuroshio Extension and atmospheric heat flux efficiencies. The Kuroshio Extension is a dynamic but relatively unstable system, with variability in the bifurcation latitude occurring on interannual time scales. The cause of these variations and their effects on the surface flow and total transport of waters has been studied extensively, with advances in SSH satellite altimetry methods allowing for observational studies on larger timescales. Studies suggest that more northerly bifurcation latitudes have been historically correlated with greater surface water transport and mode water formation, pertaining to the direct flow paths closer to the coasts of Japan and Taiwan during the wintertime months.

Climate Change
Climate change, specifically considering increasing sea surface temperatures and decreasing salinities, has been predicted to strengthen the surface flow of the Kuroshio Current as well as other WBCs across the Pacific. These changes are principally thought to be a product of wind stress and surface warming resulting from the increased stratification of the surface layers of future oceans. The predicted lasting effects of warming surface oceans starkly contrast between the Atlantic and Pacific oceans, where the Atlantic will experience a slowing of AMOC circulation while the Pacific WBCs, including the Kuroshio Current, will strengthen. This is a result of a potential poleward shifting of westerly winds within the Hadley Cell, increasing the total wind stress curl on the subtropical gyre. The effects of these predictions caused an increased geostrophic circulation and subsequently an intensification of the northern part of the Kuroshio Current, increasing flow velocities by almost double. In addition, one study used predictions from the Coupled Modeled Intercomparison Project (CMIP5), which predicted the flow to be strengthened from its point of bifurcation near the equator all the way to the Kuroshio Extension and ultimately interacting with the subtropical gyre, which contrasts older predictions of simply gyre forced acceleration. Increased stratification and the strengthening of the surface layer allows the opposite to occur in the deeper layer of the Kuroshio Current, which is proposed to slow. The exact mechanics causing this change are not well understood, however "cyclonic winds" within the gyre in addition to increased stratification near the surface is theorized to be the cause. Finally, the general observed southward migration of both the NEC and SEC subcurrent bifurcation latitudes over the past thirty years has been consistent with a strengthening of WBC currents. With shifting winds and increased gyre circulation, bifurcation latitudes are predicted to continue southward migration contributing to the increased flow.