The calcium carbonate saturation state is decreasing globally in the surface waters due to the increase in carbon dioxide in the atmosphere and dissolved carbon dioxide in the oceans. Recent evidence suggests that the calcium carbonate saturation horizons in the deep water of Atlantic, Pacific, and Indian Oceans are shoaling due to this influx of anthropogenic carbon to the water. The marginal seas, including the Mediterranean, Caribbean, and Gulf of Mexico, have limited inorganic carbon data to map these saturation horizons or observe the changes in depth due to anthropogenic carbon. The aragonite saturation horizons (ASH) at stations throughout the deep water of the Gulf of Mexico (GOM) were observed at an average depth of about 500m. This is much shallower than the ASH in the northwestern Atlantic (~3000m). The ASH in the GOM also gets shallower from east to west across the basin. This is due to acidified source water entering and filling the Caribbean basins and flowing into the GOM and also due to respiration occurring in the GOM.
