Interaction between sea and air monitored

A new observatory has been opened in tropical Cape Verde to monitor interactions between the atmosphere and the tropical oceans and their links with climate change.

The international observatory, located on the island of São Vicente in the tropical east Atlantic Ocean, began its working life in October 2006 and has already produced three months of atmospheric data.

It was formally opened on January 9 by Madalena Brito Neves, the Cape Verdean Minister of Environment and Agriculture.

The new observatory will monitor and measure changes in the chemical, biological and physical composition of the tropical ocean and the air immediately above it, the marine boundary layer. Very few scientific studies have been carried out in this region – we know more about what is happening at the poles than in the tropics – so the observatory will help to fill a knowledge gap.

The observatory is funded through the Natural Environment Research Council’s (NERC) Surface Ocean-Lower Atmosphere Study programme (UK SOLAS). Partner organisation Leibniz Institute of Marine Sciences, (also known as IFM-GEOMAR), in Kiel, Germany, is providing additional funding and support through the Federal Ministry of Education and Research (BMBF) large-scale project SOPRAN (Surface Ocean Processes in the ANthropocene) and the EU Tropical Eastern North Atlantic Time-Series Observatory (TENATSO).

Dr Philip Newton, deputy science & innovation director at NERC, emphasised the scientific and societal importance of global monitoring networks.

“20 years ago, increases in carbon dioxide measured using long-term observations on Hawaii demonstrated that far-reaching changes in atmospheric composition, of the sort that are now driving national and international policies, were already underway,” he said.

“The new information provided by the Cape Verde observatory will greatly widen our window of knowledge, with benefits not only to Africa but also to the UK and the rest of the world.”

Increased levels of methane, nitrous oxide and halocarbons together contribute nearly as much to global warming as carbon dioxide. But these gases survive for a much shorter time in the atmosphere and we need to know their removal rates as well as their concentration and production rates.

Tropical oceans cover about a third of the Earth’s surface and the air immediately above them contains very high levels of the main atmospheric oxidant – the hydroxyl radical. These radicals act as a cleaning agent, breaking down greenhouse gases such as methane and nitrous oxide. About 75% of methane removal is thought to occur in the tropics.

Dr Lucy Carpenter from the University of York, lead scientist for the project, said: “The tropical marine boundary layer acts as an engine room for the self-cleansing of the Earth’s atmosphere, but we know little about what’s going on there.

“These regions are also a ‘net sink’ for low-level ozone and many dangerous greenhouse gases; that is, where they are broken down, rather than created. The potential for atmospheric and oceanic change is large in this region, so the information we get from the observatory will be invaluable.”

New ocean-based activities will start in the summer of 2007 with the installation of an ocean station – a network of buoys and moored instruments – about 70km offshore.

The station will monitor the temperature, salinity and nutrient content of the sea-water, as well as levels of carbon and oxygen and the productivity of marine organisms such as phytoplankton.

The tropical sea is one of the places where sea-surface temperatures are rapidly changing, lowering amounts of phytoplankton which soak up large amounts of carbon dioxide, directly resulting in differing levels of trace gases present in the atmosphere.

Dr Carpenter and her colleague, Professor Alastair Lewis, also from York, have been the major drivers for the project in the UK. They are working closely with Professor Douglas Wallace from the Leibniz Institute.

Professor Wallace, who co-ordinates the TENATSO and SOPRAN projects, said: “A recent study showed large decreases in the biological productivity of the tropical Atlantic, as measured by satellites.

“Major changes are going on in this region and it is therefore timely that we can now directly observe these changes both on the ground and at the sea-surface. Years of effort by many groups, including our Cape Verde partners, have gone into the planning of the observatory. It is very exciting for us to see the data start coming in.”

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