11/30/2015D. Nincic CMA Climate Change Four ocean issues

04/21/23 D. Nincic CMA

Climate Change

Four ocean issues


Climate Change: Four ocean issues• Impact on the ocean as a carbon dioxide

absorber

• Ocean Acidification

• Impact on the ocean as solar heat distributor

• Impact of sea level rise on coastal areas


The role of the oceans: CO2 absorption• The oceans serve as a vast “sponge” or “sink”

for carbon dioxide

• Approximately 7 billion metric tons of carbon are added to the atmosphere each year

• Only 3 billion of these tons remain in the atmosphere – 2 billion are absorbed into the oceans; the remainder into terrestrial plants


Additional impact of global warming

• There are concerns that global warming could impede the ocean’s ability to absorb carbon dioxide from the atmosphere; leaving more greenhouse gases in place

(“Emission cuts ‘vital’ for oceans” BBC.co.uk)


Important Concern: Ocean Acidification• Ocean acidification, due to increasing

atmospheric carbon dioxide has already increased the acidity of the world's oceans to a level that is irreversible in our life times.

• The world's oceans have already absorbed about half of the CO2 produced by humans, mainly by the burning of fossil fuels, over the past 200 years.



Impact of Acidification

• Scientists fear the rising acidity of seawater will have a particularly detrimental effect on corals and other marine organisms, because it will be harder for them to form their skeletons and shells.

• Tiny shelled plankton in the Antarctic Ocean that are a major food source for fish and other animals are likely to be among the first to suffer.

• Higher CO2 levels will also make it harder for many marine fish and shellfish to breathe and reproduce.



The Process


The Stages

1. Up to one half of the carbon dioxide (CO2) released by burning fossil fuels over the past 200 years has been absorbed by the world's oceans

2. Absorbed CO2 in seawater (H2O) forms carbonic acid (H2CO3), lowering the water's pH level and making it more acidic

3. This raises the hydrogen ion concentration in the water, and limits organisms' access to carbonate ions, which are needed to form hard parts


Copenhagen Summit 2009

• “Acidification of the oceans is a major threat to marine life and humanity's food supply”

• “It affects marine life, it affects coral, and that in turn could affect the amount of fish in the sea – and a billion people in the world depend on fish for their principal source of protein”


The role of the oceans: Climate regulator

• Without the ocean’s current system, the equator would be hotter than it is, and the poles would be colder

• The ocean distributes the sun’s heat



Slowing the conveyor belt

• Anything that prevented the waters of the conveyor belt from cooling, or that made them less salty, would prevent them from sinking

• Thus slowing or stopping the movement of the conveyor belt currents

• For example: Increased rainfall or arctic ice pack melting


Arctic ice pack melting

• NB: Multi-year ice is fresh, not saline

• 2002 record year for Arctic ice loss – double the loss observed in 1992• 40% decline in draft of ice pack• 20% loss in pack area since 1978

• Predictions of summertime “ice free” Northwest Passage by 2050 (some estimate earlier)


Role of air pollution

• Smog (particularly ozone) was responsible for one-third to half of the observed warming trend in the Arctic during winter and spring

• Ozone is transported from the industrialized countries in the Northern Hemisphere to the Arctic quite efficiently during these seasons

• (Paper forthcoming, American Geophysical Union's Journal of Geophysical Research-Atmospheres)


Impact on the Conveyor Belt

• Researchers from the UK's National Oceanography Centre say currents derived from the Gulf Stream are weakening, bringing less heat north• Note: This means more heat remains in the Atlantic

impact on hurricanes

• Computer models have predicted that if the conveyor belt turned off completely, Europe would cool by perhaps four to six degrees Celsius.

• Source: BBC, “Ocean changes ‘will cool Europe’,” 30 November 2005


Further Details

• Florida-based scientists monitor the northwards-flowing Gulf Stream, and have found it has remained roughly constant over the last 50 years

• But, scientists studying the southward flow of the water have noted a 30% decline of the deep cold water

• Result: Less overturning of water; more heat remains in the tropics and less becomes distributed to Europe


Potential impacts

• Europe could become considerably colder

• Ireland could have about the same temperature as Spitsbergen

• Much of northernmost Europe could become largely uninhabitable

• Severe impacts on agriculture


Not just the Arctic….

• Antarctica is losing 152 cubic km of ice each year

• This loss of ice equates to an annual rise in the global average sea level of 0.4mm; • the total rise, due mainly to thermal expansion

of seawater, is estimated at about 1.8mm per year (“Antarctica losing ice to oceans,” BBC, 2 March 2006)


Sea level rise: Some UN predictions

• Seas rose 10” in the 20th century

• UN IPCC estimates: An additional 12” – 40” by 2100

• Note: These are averages; sea levels will drop in some places (as seen in Alaska)


Source: BBC


Sea Level Rise: Examples of vulnerable areas

• Bangladesh

• Micronesia

• Nile Delta


Potential impact on Bangladesh



The Nile: One half meter



Possible impacts: The United States• Loss of 10,000 square miles of coastland with a 2’ rise

• Smith Island in Chesapeake Bay may disappear

• Loss of 100s of feet of East Coast beaches

• One third of the Everglades sits less than 12” above the Atlantic

• Much of New Orleans, and San Jose and Long Beach, Calif., are already below sea level (as we well know)



Tying it all together

• Global warming contributes to environmental stresses (as well as economic, social, and political stresses)

• Ocean Examples: • Coral reefs• Loss of biodiversity

Documents

11/30/2015D. Nincic CMA Climate Change Four ocean issues