Steve and Bill, all well and good if this was the only, let alone the best solution. Sequestering this excess carbon in plant life instead provides food, fuel and fibre for the 10 billion expected on the planet in 40 years. I don't see much ancillary benefit from calcium carbonate or sea urchins.
A study lead by Yadu Pohkrel determined “The drawing of water from deep wells has caused the sea to rise by an average of .77 millimetres every year since 1961,” which is about 42 percent of the total.
A recent BC study co-authored by Diana Allen, a professor of earth sciences at SimonFraserUniversity, confirmed Dr Pohkrel’s finding and notes low lying crop lands in B.C. are at risk as a consequence. It further notes, “about half of British Columbia’s food supply is imported, much of it from California, which has suffered from drought and is projected to become even more reliant on groundwater as precipitation declines due to climate change.”
The province of British Columbia needs to revisited its policy prohibiting bulk water sales because; as the Allen study notes, mining’ groundwater could help fuel climate change, the outflow from Link Lake (the average annual rainfall of 33 feet there sends enough water into the Pacific Ocean to meet all of California's water needs for the next 20 years) to say nothing of other provincial sources contributes to sea level rise at the same time as California suffers drought, the pumping of aquifers to counteract the drought compounds the sea level problem, local food supplies are at risk due to this miss match, sequestering water that would otherwise produce sea level rise in depleted aquifers and crops saves us from having to spend as much to mitigate the sea level problem - a provincial report says Metro Vancouver alones needs to spend $9.5 billion by the end of the century - and exporting our excess would provide a significant revenue stream to the province.
It makes little sense to be drowning while the source of much of your food supply is dessicating.
Besides these two benefits, I have patent applications in the works for four other ways to mitigate the sea level and carbon problem.