Recent decrease of summer nutrients concentrations and future possible shrinkage of the subarctic North Pacific high-nutrient low-chlorophyll region

We found evidence that summertime surface nutrient concentration in the subarctic North Pacific (SANP), the third largest high-nutrient and low-chlorophyll'' (HNLC) region in the world oceans, has decreased during 1975 to 2005. The observed trend seemed independent from natural decadal/interannual variations and roughly explained by the combination of multidecadal increasing trend of sea surface temperature (SST) and the observed negative correlation of nutrient concentration vs. SST. These analyses indicated that the observed decrease is mainly due to the recent stratification of the upper ocean column caused by global warming. This nutrient trend has a potential to minimize the present SANP-HNLC region by up to 25%, assuming that the observed trend continues until the end of this century.