Global change is defined by “a transformation that occurs on a worldwide scale (e.g., an increase in carbon dioxide in the atmosphere) or exhibits sufficient cumulative effects to have worldwide impact (e.g., local species extinction resulting in global loss of biodiversity).”
credit: www.pbs.org/strangedays/glossary/G.html
Climate change
Credit photographs and picture from left to right: http://www.foe.co.uk/campaigns/climate/; http://www.fragilecologies.com/aug22_05.html; http://ies.jrc.cec.eu.int/252.html
One important transformation that is a burning subject today is climate warming. In this respect, oceans which cover three quarters of the earth’s surface are to be considered: This liquid mass plays a fundamental role in the earth’s climate by a number of aspects and the way it will react to climate warming is of consequent importance.
In fact, oceans act as climate regulators either directly by transferring heat through surface currents (e.g. the Gulf Stream) for example, or indirectly, through CO2 absorption.
Icecaps, which also play a crucial role in the global climate system, are already being seriously affected by climate warming. According to the Green Paper published by the European commission in June 2006, “climate warming of the Artic region is two or three times more marked than elsewhere on the planet, with a 3°C increase over the past 50 years”. Moreover, Artic pack ice has already shrunk consequently. These major changes will with no doubt have significant impacts on the local flora and fauna including the entire food chain and therefore affect indigenous people.
Artic changes do not only have local consequences, they impact the planet as a whole by the sea level rise and the increase of temperature. In fact, since about 12 years the rising of the sea level has accelerated to 3 mm/year whereas it used to be only 1.8 mm/year. (Sebastián Escalón, Le journal du CNRS, July-August 2006)
“Safeguarding the Artic region’s climate is a very important part of averting global climate change” (Green paper) and it is therefore at the centre of the E.U.’s strategy to combat climate change.
Climate warming could also have an impact on oceanic currents. In fact, oceans have the capacity to store heat better than land and distribute this heat around the world through deep-sea and surface currents (e.g., the Gulf Stream). However, according to Herlé Mercier, research scientist at the Laboratoire de Physique des oceans in Plouzané (partner #2), the Gulf Stream might be slowed of about 25% by the year 2100. Impacts on Europe of such a major change may be quite serious as summer temperatures will tend to rise, coastal zones will increasingly be vulnerable to storm surges and tourism may therefore be affected. “Provisions of water through desalinisation may well be increasingly needed around our coasts.” (Green paper). Biodiversity will most probably be affected as major species shift are to be anticipated. As a result, fish abundance and distribution may be affected and therefore the fisheries sector also.
The sea also plays a vital role in carbon cycle which has a capital role in climate as it acts as a sink which stores over 90 % of all the carbon on the planet. Phytoplankton has an important function in this role as it captures atmospheric CO2 thanks to photosynthesis. Carbon is then passed on through the food chain and becomes fixed. “However, this action of the oceans in absorbing carbon is not homogeneous or constant. […]As increasing demands are being made upon this storage function – due to the growing and cumulative amounts of CO2 discharged in the atmosphere by human activities – we are seeing signs of an acidifying aggression throughout the marine biosystem.” (Credit: RTD info, February 2006)
Coral Bleaching
photography by Ray Berkelmans http://www.reeffutures.org/topics/bleach.cfm
This acidification of the oceans due to global change can already be seen on coral reefs, for example, as they are bleaching. These acidic conditions have a dissolving effect on the shells of many calcarian organisms and might also cause the extinction of species like pteropods which envelope is made of aragonite (a type of limestone).
For biodiversity, consequences of global change are incalculable as if one species disappears the whole food chain will be affected and might cause the decline of an entire ecosystem. Being able to look into the marine organisms’ genome is interesting to scientists as it help to understand their physiology and how genes are regulated in different conditions of stress. Data generated by genomic studies could enable scientists to predict whether or not they will be able to survive or adapt under changing environmental conditions.
Oceans and Climate
Researches between Air and Sea
Ice Flow: Today threatened, ice flow and highly isolating and slow heat exchanges between oceans and atmosphere. They enable oceans to stay warmer during winter. Satellites: Satellites provide very usefull indications to establish models like the measure the rise of the sea level and their cartography. They are also used to transfer the information received from the buoy to the research laboratories. Surface exchanges: At the surface of the oceans, exchanges of water and heat are permanent. "Anormal" changes in the temperature of the surface waters can have important consequences in climate and can provoke hurricans for example. Gas Hydrates: These ices imprison enormous quantities of methane, a gas that has an important glasshouse effect... In the past, brutal degassing may already have provoked important climate changes. Submarine volcano: According to recent studies, hydrothemal vents are suspected to reject methane into the atmosphere, which would increase the glasshouse effect. Buoys: The Argo buoys are released in the oceans and are drifted along the currents. They can go as deep as 2000 meters deep and are able to measure levels of salinity and temperature for example. The Buoys regularly come up to the surface to transfer these data to a satellite. Oceanographic cruises: More and more oceanographic cruises are organized around the world for different purposes. Some are organized to go drill the bottom of the ocean and collect information about past climates. The Biological pump: In the top layers of the water column, carbon is used by phytoplankton which is then eaten by zooplankton. This food chain drags important quantities of carbon to the depths of the ocean in the form of sediments. Rates of CO2 in the atmosphere are thus limited. Physical pump: Important marine currents drag enormous quantities of carbon (captured at the surface) into the depths of the ocean. A part of it will then be reconducted to the atmosphere. These currents also carry an important part of the heat received by the Earth.
© Illustration: A. Dagan for Le Journal du CNRS / Text: M. Ravaud translated by Stephanie Ries. Documents extracted from Le journal du CNRS, n° 198-199 July- August 2006
References:
Green Paper: Towards a future Maritime Policy for the Union: A European vision for the oceans and seas “How inappropriate to call this planet Earth when it is quite clearly Ocean” attributed to Arthur C. Clarke (presented by the Commission). Brussel, 7.6.2006, COM(2006) 275 final, volume II – Annex
Océans et Climat, l’équilibre menacé. Le Journal du CNRS. N°198-199 juillet-août 2006. pages 17-27. electronic version :http://www2.cnrs.fr/presse/journal/
Contributed by Stephanie Ries
