Seasonal and Interannual Variability of Nitrate in the Eastern Chukchi Sea: Transport and Winter Replenishment
There is considerable interannual variability in transport over the northeastern shelf of the Chukchi Sea that is driven by northerly (weakens transport) and southerly (strengthens transport) wind events. In recent years, there has been an increase in southerly wind events that may be reinforced by warming of arctic shelves. As these conditions enhance total transport and nutrient flux through Bering Strait, contemporary Bering Sea water is advected onto the northern Chukchi Sea shelf. During winters with highest transport (2010 – 2011, 2017 – 2018), pre-bloom (May 15) nitrate concentrations were high and closely resembled nitrate concentrations in the Bering Sea. Anomalously low nitrate concentrations were observed in the winter of 2011-2012 when transport was negligible. In the presence of southerly wind events, nutrient measurements in the northern Bering Sea can be used to forecast pre-bloom nitrate concentrations available for sustaining primary production in the eastern Chukchi Sea. Since 2005, inorganic nitrogen concentrations in the northern Bering Sea have varied between 11 – 22 µM, an indication that net community production over the eastern Chukchi Sea may have varied by 50% during this time.