We show that ocean acidification from fossil fuel CO2 invasion and reduced ventilation will result in significant decreases in ocean sound absorption for frequencies lower than about 10 kHz. This effect is due to known pH-dependent chemical relaxations in the B(OH)3/B(OH)4- and HCO3-/CO32- systems. The scale of surface ocean pH change today from the + 105 ppmv change in atmospheric CO2 is about -0.12 pH, resulting in frequency dependant decreases in sound absorption (α = dB/km) exceeding 12%. Under reasonable projections of future fossil fuel CO2 emissions and other sources a pH change of 0.3 units or more can be anticipated by mid-century, resulting in a decrease in α by almost 40%. Ambient noise levels in the ocean within the auditory range critical for environmental, military, and economic interests are set to increase significantly due to the combined effects of decreased absorption and increasing sources from mankind’s activities.
Archive for September 24th, 2008
We use a coupled climate/carbon-cycle model to examine the consequences of stabilizing atmospheric CO2 at different levels for ocean chemistry. Our simulations show the potential for major damage to at least some ocean ecosystems at atmospheric CO2 stabilization levels as low as 450 ppm. Before the industrial revolution, more than 98% of corals reefs were surrounded by waters that were >3.5 times saturated with respect to their skeleton materials (aragonite). If atmospheric CO2 is stabilized at 450 ppm only 8% of existing coral reefs will be surrounded by water with this saturation level. Also at this CO2 level 7% of the ocean South of 60ºS will become undersaturated with respect to aragonite, and parts of the high latitude ocean will experience a decrease in pH by more than 0.2 units. Results presented here provide an independent and additional basis for choosing targets of atmospheric CO2 stabilization levels.
Continue reading ‘Atmospheric CO2 stabilization and ocean acidification’