13 effects on oceans - updated

Climate Change Effects on Marine Systems

Effects on Marine Systems - Circulation

• The “Achilles’ Heel” of the climate system.



• The Gulf Stream brings warm, salty water to the north – it’s an oceanic heat pump.

• The loss of this heat would cool the North Atlantic region by 3-5° C.

• A critical component of this is the sinking limb of the conveyor which is driven by density.




• The scientific community does not expect the conveyor to shut off as a result of global warming!

• What is more likely is that existing Arctic ice will melt at a rate that buffers the warming at high latitudes.

• But once that ice is gone …


• Another circulation system that could be affected by global change is the El Niño – Southern Oscillation.


• A typical El Niño event causes between 2 and 7 billion dollars in economic damage.

• Usually due to some combination of drought, flooding, and storm damage.


• Trade winds blowing from east to west pile up warm water in the western Pacific (Western Warm Pool). Pool of warm water generates a lot of precipitation for this region (Indonesia, Philippines, etc.)


• Trade winds greatly weaken or even reverse direction allowing Warm Pool waters to “slosh” back towards the east.


• First observed by South American fishermen – the anchovies would vanish around December.

Normal

El Niño




• Less intense hurricane season in the Atlantic.

• More intense hurricane season in the Pacific.


• Essentially an enhancement of “normal” conditions. Results in weather anomalies that are basically the opposite of those caused by El Niño.

La Niña

Normal

El Niño




• El Niños used to occur every 4-7 years.

• But since the early-1970’s they have occurred every 2-5 years.

• A lot of research on whether that change in frequency is related to human impact on climate.

Effects on Marine Systems - Ecosystems

• El Niños also have a strong effect on ecosystems.

• Warm water where they are normally cooler cause organisms to move deeper to cooler temperatures.

El Niño


• Many fish move deeper, resulting in massive sea bird mortality during El Niño events due to starvation.


http://video.nationalgeographic.com/video/player/environment/environment-natural-disasters/landslides-and-more/el-nino.html


• Increased temperature (not just due to El Niño) a problem for many marine ecosystems.

• Similar to freshwater ecosystems, warmer temperatures impact organism distribution, metabolism, and gender ratios.


• Temperature and coral reefs - “coral bleaching.”


• Temperature and coral reefs - “coral bleaching.”



• Corals are small animals that secrete a calcium carbonate skeleton.

• Many coral species have symbiotic algae living in their tissue called zooxanthellae.


• Corals are small animals that secrete a calcium carbonate skeleton.

• Many coral species have symbiotic algae living in their tissue called zooxanthellae.


• Zooxanthellae produce organic compounds that the coral relies on for food.

• When temperatures rise, the corals expel the zooxanthellae – makes them look white, or “bleached.”


• Without the symbiotic zooxanthellae, the coral loses 90-95% of its food supply, and usually dies within months.

• Once the coral is dead macro algae takes over, smothering the reef.



(green – no bleaching, blue – low bleaching, yellow – medium bleaching, red – high bleaching)


• Temperature effects are expected to be greater for the Arctic.


• Less sea ice means less area for seals to reproduce, less area for polar bears to hunt.

• The other big concern is ocean acidification.

• When CO2 dissolves in water it produces carbonic acid – makes the oceans more acidic.


• Lots of organisms make their skeletons out of calcium carbonate.



• Will have drastic consequences not just on the carbonate organisms themselves, but all the way up the food chain that feeds on those organisms.


13 effects on oceans - updated

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