Recent expansion and intensification of hypoxia in the Arabian Gulf and its drivers

The Arabian Gulf (also known as Persian Gulf, hereafter Gulf) is a shallow semi-enclosed subtropical sea for its extreme physical environment. Recent observations suggest decline in oxygen concentrations the over past few decades accompanied by an expansion of seasonal near-bottom hypoxia. Here, we reconstruct evolution dissolved from 1982 through 2010 and explore controlling factors. To this end, use eddy-resolving hindcast simulation forced with winds heat freshwater fluxes atmospheric reanalysis. We show that hypoxia (O 2 < 60 mmol m -3 ) emerges deeper part summer peaks autumn response to enhanced vertical stratification inhibiting mixing O replenishment at depth. also find significant deoxygenation study period, content dropping nearly 1% per decade decreasing between 10 30 early 1980s late 2000s. These changes result horizontal bottom hypoxia-prone seafloor area increasing less than 20,000 km around 30,000 lengthening hypoxic season emerging locally 1 months earlier 2000s relative 1980s. Furthermore, declining levels suboxic conditions 4 emergence amplification denitrification there. An analysis budget demonstrates essentially caused reduced solubility near surface respiration bottom. While results warming waters, mostly driven increased supply nutrients imported Sea due weakening winter Shamal period. Our findings recent local climate are not only altering environment but having strong impact on biogeochemistry profound potential implications ecosystems fisheries region.