Ocean depths may hold climate change solutions

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It is not very often that an internationally renowned oceanographer is invited to address a crowd of oil  and insurance experts, but such was the case today at M

in Dubai.

The meeting was all about the major risks that major oil companies face. Those definitely include the impact of climate change on the industry, be it directly through more frequent storms threatening offshore infrastructure, or indirectly through regulations to curb carbon emissions.

"There is as much heat in the top metre of the ocean as in the whole of the earth's atmosphere. Climate is about oceans. It is not about atmosphere,"

, the president and director of the

, told the conference.

That means, among other things, that the planetary heat transfers that drive weather patterns,   are largely determined by ocean currents. There is evidence that the "oceanic conveyer belt" governing such heat transfers, is slowing down, says Dr Knap, with major repercussions for climate change.

According to Dr Knap, coal is responsible for 40 per cent of global carbon emissions, and oil for 36 per cent. Natural gas and cement-making contribute most of the remainder.

Currently, 45 per cent of those emissions are spewed into the atmosphere, 29 per cent are absorbed by trees and other land vegetation, and 26 per cent by oceans. But oceans must be the final repository for carbon dioxide, Dr Knap argues: "We have to get it out of the atmosphere and put it into the oceans."

But there is a big snag: Dissoved CO2 makes water more acidic. That is already occurring in the world's oceans and may have caused a 30 per cent reduction in the rate at which corals lay down skeletons made mainly of the acid soluble mineral calcium carbonate.

This has a huge effect on oceanography, reaching all the way up to the Arctic, where it affects one of the planet's most important food chains, a mainstay of the balance of life on earth.

"Somehow, we have to get CO2 into the ocean without acidification," Dr Knap says. "The ocean is the ultimate carbon sink. Acidification is a pressing issue."

On the sidelines of the conference, he pointed out that seawater acidification was mainly an issue for marine life at shallow depths. That is especially true of coral reefs, which require sunlight for the symbiotic algae harboured by corals to produce food for their hosts.

That, in turn, points to deepwater sequestration of carbon dioxide as a potentially important approach to capping emissions.

Such proposals in the past have sparked controversy, but major experiments are now underway to test the feasibility of storing carbon dioxide in the ocean depths.

One approach aims at increasing the uptake of carbon dioxide by marine algae in open waters. The microscopic phytoplankton, or any marine animals that feed on them, eventually die and sink to the bottom of the ocean, carrying payloads of organic and mineralised carbon with them.

At least six large-scale tests are being carried out to determine whether "fertilising" ocean expanses that are deficient in ferrous sulphate, an essential food for marine algae, could be effective.

Desperate times require bold measures, it seems. Moreover, the results to date of such experiments

.

Even if ocean fertilisation does turn out to work, humble phytoplankton, the source of much of the earth's geological stores of oil, should not be relied upon to absorb all the world's excess carbon emissions, Dr Knap says. Unfortunately, the conditions governing oceanic algal populations are not well understood, which means unpredicted die-offs can and do occur.

If oceanographers hope to contribute to curbing climate change, they still have their work cut out, as Dr Knap would be the first to agree.

Pic courtesy of Bermuda Institute of Ocean Sciences.
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