Position of the Gulf Stream influences lake nitrate concentrations in SW Ireland

Abstract

A positive relationship was observed between winter nitrate concentrations in two lakes in SW Ireland and the latitudinal position of the Gulf Stream in the previous spring. Weaker but statistically significant relationships were apparent between the Gulf Stream position and weather variables, as well as soil moisture levels, in the same year. Wind speed, cloud cover and precipitation in May and June were negatively related to the Gulf Stream position in April. In contrast, air temperature and sunshine hours in May and June and the magnitude of the soil moisture deficit in June were positively related. There was also a positive correlation between the magnitude of the early summer soil moisture deficit and lake nitrate concentrations in the following winter. This three way linkage implies that the concentration of winter nitrate in these lakes is influenced by a sequence of related factors that are initiated by the latitudinal position of the Gulf Stream. In this sequence the position of the Gulf Stream appears to influence early summer weather in SW Ireland which in turn dictates the extent of moisture deficit in catchment soils and, consequently, the degree of nitrate loss to surface waters in the autumn. This connection, between events in the Atlantic Ocean, weather systems in the North West Atlantic and processes in catchment soils in SW Ireland has implications for both the quality and quantity of biota in lakes and catchments in the region.