Negative feedback in the cold: ice retreat produces carbon sinks in Antarctica

Marshall CallahanAtmospheric Science

By: L. S. Peck, D. K. A. Barnes, A. J. Cook, A. H. Fleming and A. Clarke

Overview• Purpose of Research• Importance of Research• Background Information• Data/Methods• Results• Conclusions• My Opinion• Questions

Purpose• Find out if loss of sea ice is counteracted by

increase in marine ecosystems for global warming

Why is this Important?• Could Provide a new variable to take into account

when estimating future global CO2 levels

Antarctica

Antarctica

Sea Ice• Can reflect around 70% of incoming Shortwave

radiation (Acts as a negative feedback)

Melting Sea Ice• The melting of sea ice acts as a positive feedback

for global warming• Less Sea Ice = Less reflected short wave radiation

Marine Ecosystems• All based off of phytoplankton or zooplankton =>

other animals (nekton and benthic)

Benthic Nekton

Marine Ecosystems• Act as a carbon sink producing a negative

feedback• An increase in amount of biomass can take more

carbon out of the atmosphere

Unanswered Questions

• Timescale of moving carbon from atmosphere to new marine ecosystems around Antarctica

• Effect on total carbon cycle

• Uncertainty due to other factorso Nutrient release from sea-iceo Role of Antarctica Circumpolar Current

Data/Methods• Use of Satellite images, preexisting charts, and

averaging for the retreating of sea ice estimation

1950 Ice Front

2008 Ice Front

200m Isobath

Data/Methods• Used Sea WiFS (satellite) measurements to

determine plankton amounts• Red = Higher concentration

Data/Methods• Measurements of plankton at depths deeper than

satellites can view over a year

Peak Season

Results• More area opened to phytoplankton

productivity due to increase in open ocean

• Around 23,900 km² of near shore area (200m or less) uncovered since 1950’s along Antarctica Peninsula

• From the 1980’s18,800 km² now has phytoplankton productivity that did not before

(About the size of Rhode Island, Connecticut, and Delaware or New Jersey)

ResultsEstimates of Carbon held in each type of biomass in the Ecosystem around Antarctica Peninsula (Total > 4.1 x 10⁵ tonnes)

• Use other studies estimates then scale to area of lost sea ice (176 gCm⁻² and 109 gCm⁻²)• 1 tonne = 1000 kg

Results• Once the Carbon has entered the marine

ecosystem it becomes very unlikely that it will be reintroduced into the atmosphere

• Noted the benthic productivity can vary greatly, however the chances for it to happen around Antarctica are slim

Results• These new marine ecosystems act as a one-time

carbon sink that has a limit, not as a continuing feedback

• Once limit has been reached no more carbon can be added.

Results• Unable to determine how much carbon comes

from deep ocean currents or from the atmosphere

Conclusions• Melting of sea ice around Antarctica Peninsula

allows for the development of new marine ecosystems

• These new ecosystems act as a limited carbon sink that can hold from 3.85 x 10⁵ to 2.36 x 106 tonnes

• What seems like a influential carbon sink is actually smallo Total sink from Antarctica peninsula would only be around 11% of the

carbon sink created by the expanding boreal forests (~8.4 x 106 tonnes)

Conclusions• Some species have experienced faster growth

rates due to increase of carbon in environment• Hard to predict flow of carbon and timescale of

flow• Glaciers/Ice shelves around the Antarctica

Peninsula occupy < 1% of the total area of glaciers/Ice shelves of Antarctica

• Unpredictability of future events

My Opinion• Interesting predictions on new carbon

sinks/negative feedback• Actually compare affect between sea albedo

to carbon sink on climate• Carbon Cycle• Apply to other areas (ex: Antarctica, other

near shore sea ice)• Boils down to time and money

o Paying for research vessels to test o Time to study relationships

Qué?