by the upwelling at the periphery and the convective mixing caused by the cooling of surface water as the rings move north of the current. The thermostad is the deep mixed layer that has discrete boundaries and uniform temperature. Within this layer, nutrient-rich water is brought to the surface, which generates a burst of primary production. Given that the water in the core of a ring has a different temperature regime than the shelf waters, there are times when a warm-core ring is undergoing its spring bloom while the surrounding shelf waters are not. There are many complex interactions within warm-core rings and thus, lifetime productivity is not very different from the surrounding shelf water. A study from 1998 found that the primary productivity within a warm-core ring was almost the same as in the cold jet outside it, with evidence of upwelling of nutrients within the ring. In addition, there was discovery of dense populations of phytoplankton at the nutricline within a ring, presumably supported by the upward mixing of nutrients. Furthermore, there have been acoustic studies in the warm-core ring, which showed intense sound scattering from zooplankton and fish populations in the ring and very sparse acoustic signals outside of it. Typhoons Typhoons can produce intense winds which push on the surface layer of the ocean for brief periods of time. These winds induce the warmer surface layer of the ocean to mix with the deeper cooler layer of water that is situated below the pycnocline. This mixing introduces nutrients from deeper cooler water to the warmer surface layer of the ocean. Organisms such as phytoplankton and algae use these newly introduced nutrients to grow. In 2003, two typhoons induced significant surface layer mixing as they passed through the region. This mixing directly produced two algal bloom events in the North Western Pacific Ocean that negatively affected Japan. Nutrient transport The Kuroshio Current is considered a nutrient stream because of high nutrient flux from surrounding oligotrophic waters with primary production of 150 to 300 grams of carbon per square meter per year based on SeaWiFS global primary productivity estimates. The current transports significant amounts of nutrients to support this primary production from the East China Sea continental shelf to the subarctic Pacific Ocean. The maximum chlorophyll value is found around depth. Its importance in nutrient transport is demonstrated by the nutrient rich water in the Kuroshio Current is