How Will Global Warming Change Our Oceans? A Quick Primer


photo: Mel Silvers via flickr

When it comes to climate change science it seems like each new week brings a fresh study showing how much crop yields are going to decline, how much less water many places are going to have, how quickly sea level rise is going to happen, how many more infectious diseases are going to spread, et cetera, et cetera. In short, just how bad things could get. With the UN climate talks just about three months away now, it seemed appropriate to round up some of these, starting with oceans:
Fishermen in southern Bangladesh, photo: b k via flickr.

Sea Level Rise = 1 Meter by 2100, More Past That


Sea level rise is undoubtedly one of the most publicized and easily visualized effects of climate change -- there are a couple different interactive sea level rise simulators out there should you want to check how much sea level rise it'll take to make, say, south Florida, uninhabitable. However, just how quickly the water laps at our feet and when it'll reach our waists depends on a number of variables.

Ocean Warming 50% Greater Than IPCC Report
At the Copenhagen Climate Congress back in March, the synthesis report produced says that current estimates show that ocean warming is 50% greater than had been reported in the 2007 IPCC report and that sea level rise reported in previous decades had largely been the result of thermal expansion.

However, since 1993 the contribution of melting ice in Greenland and Antarctica (more on these in a moment) has been growing. The exact speed with which these are going to contribute to sea level rise is highly uncertain, the synthesis report says, but the best scientific estimate -- based on observed correlation between global average temperatures and sea level rise over the past 120 years -- shows that by 2100 we will experience sea level rise of one meter or more. At the absolute minimum sea level rise of 50cm could occur.

The thing to keep in mind is that this amount of sea level rise is only by 2100 and that once set in motion it will continue past that -- through 2200-2300 we could easily experience sea level rise in excess of five meters.

What that means in terms of human impact is at minimum 10% of the world's population will be directly affected by sea level rise.

20% of Nile, Mekong Deltas Submerged, Imperiling Current Food Supplies
We've recently seen stories about what this will mean in the Nile Delta and Mekong Delta (not to mention the oft-publicized and very genuine plight of Bangladesh):

Under the best-case scenarios 20% of the Nile Delta (the source of two-thirds of Egypt's food) could be submerged, and that land which remains above water could be affected by increased salinization of groundwater. In the Mekong Delta, 20% of the land could be submerged, with 10% of Ho Chi Minh City going underwater.

And this obviously leaves out the threats to low-lying island nations in the Indian and Pacific Oceans.

Coastal Flooding to Increase in Less Obvious Areas
In case you need a closer to home example (and one note as obvious as the Mississippi Delta...): An assessment of the impact of sea level rise on New York City showed that by 2080 coastal flooding which historically had been experienced every 10 years, would now occur every 3, and the statistical "once in a century" storm would more likely become the 
"once every 10-35 years" storm.


photo: Christian Revival Network via flickr

Arctic & Antarctic Ice Melting, More


Back to that Arctic and Antarctic ice melting. Recently we've seen a number of very compelling reports of just how fast melting is occurring, particularly in Antarctica -- one example being the Pine Island Glacier, which evidence shows is now melting four times faster than it was a decade ago. In fact, previous estimates showed that the glacier would take 600 years to melt, but newer data shows it could be gone in just 100 years.

Two-Thirds West Antarctic Ice Sheet = 3.3 Meters Sea Level Rise
What's more, though it's not likely to disappear entirely, about two-thirds of the West Antarctic Ice Sheet could well melt -- at some point past 2100 -- alone contributing about 3.3 meters to global sea levels.

In the Arctic, while this summer may not set a record for ice loss, the trend is solidly towards ice free summers -- some scientists saying that we're 20 years ahead of schedule, based on past predictions, as to when that will occur.

Arctic Ice Melt Triggers Permafrost Melt + Methane Release
Perhaps the bigger thing though in a warming Arctic is melting of permafrost and the released of the methane trapped in it. Considering that it appears that melting Arctic ice contributes to permafrost melt farther inland than previously thought, this is really something to be concerned with -- even though pictures of polar bears on lone ice floes capture people's imagination.

In case you don't know, the thing with methane is that it's 25 times more potent in terms of warming potential than carbon dioxide. And though atmospheric methane levels had been more or less stable in recent years , they have been observed to be increasing again, with unusually warm temperatures in Siberia being one of the culprits.


Coral bleaching photo: Samuel Chow via flickr.

Ocean Acidification & Coral Bleaching


But it's not just in high latitudes that things are going and could well continue to go haywire: It may not get as much attention, but ocean acidification and the effects of coral bleaching could be devastating.

Fellow TreeHugger John Laumer recently described what's happening as a "carbon bomb", devastating marine life as the world's oceans have become 30% more acidic than they had been. Some reports show that ocean acidity could triple by 2100.

All of SE Asia Coral Gone by 2100, Millions' Food Supply at Risk
In terms of direct human impact, and in just one region of the world: A recent report by WWF shows that without strong action to prevent it, by 2100 all the corals in the so-called "Coral Triangle" of Southeast Asia could be wiped out, causing a decline of food production in the region of 80%. That's the food supply for some 100 million people.

This also has a knock-on effect: As food security declines and poverty increases, these people will end up migrating to urban areas in search of work -- further stressing areas already trying to adapt to changing climate and building enough infrastructure to accommodate these newcomers.

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Really that's just the tip of the issue: Climate change is likely to increase ocean dead zones (up to 10 times by some estimates). It may lead to more polluted Arctic waters as currents shift. Melting Arctic ice could lead to, at minimum, wars of words over who owns newly opened ocean territory.

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Tags: Blue August | Global Climate Change | Global Warming Effects | Oceans

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