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 user 2007-12-19 at 3:58:00 pm Views: 80
  • #21060

    Ice boat details ozone collapse
    dramatic springtime collapse of surface ozone in the Arctic has been
    documented by scientists.Observations from a boat that drifted with the
    ice across the North Pole show the gas can disappear in just days.Dr
    Jan Bottenheim told a US conference that the precise chemical reactions
    involved were not fully understood.However, he said any changes to
    these processes as the Arctic warmed might limit the region’s ability
    to deal with pollutants in the atmosphere.”Ozone is the source for the
    ‘vacuum cleaner of the atmosphere’ – the molecule OH. So if we don’t
    have as much ozone, we can’t make as much hydroxide. If we then pump
    pollutants from mid-latitudes into the Arctic, they may just stay
    there,” explained Dr Bottenheim.”But a lot of this is speculation at
    the moment because so much of this information is new and we are not
    sure what to make of it.”

    Spring sunshine
    The ozone studied
    by Dr Bottenheim and colleagues at Environment Canada is distinct from
    the gas high up in the stratosphere that has been damaged through the
    release of reactive chlorine compounds by industrial society. The
    group’s ozone exists at ground level – or, in the case of the Arctic,
    at ice level – in the first 100-200m of air.In the winter, the
    concentration of the three-atom oxygen-molecule in this still air is at
    normal levels; but as the sunlight returns to the polar north in the
    spring, chemical reactions are set in train that reduce the ozone in
    dramatic fashion.Dr Bottenheim told BBC News: “In a city, in the
    evening the ozone will react with exhausts from cars and can go down
    from, say, 40 to five or even one [units of ozone]; but in the Arctic
    we’ve seen it go to 100 times less than one, which is an incredibly low
    level that I don’t think has been seen anywhere else.”And once it goes,
    it can go very fast. It can go in almost a day.”

    Ice changes
    ozone instrument on the Tara schooner observed one period in late April
    of this year when there was virtually no ozone for a period of more
    than 15 days.Whereas stratospheric ozone is depleted though an
    unnatural process involving chlorine; the ice-level ozone falls victim
    to reactive bromine atoms released quite naturally from briny Arctic
    waters. In perfect conditions, the chemistry produces an explosion of
    bromine oxide (BrO), which is detectable by over-flying
    satellites.Scientists are now trying to determine how the ozone
    behaviour might change in a rapidly warming Arctic.Conditions that lead
    to more slushy ice, which could assist the release of bromine, might
    result in more extensive periods of ozone loss.”It’s a possibility, but
    as I say this is still speculative,” stressed Dr Bottenheim.The
    consequences of any change needed to be understood, he added. It is
    known from observations, for example, that the depletion of ozone at
    the same time also causes a depletion of gaseous mercury, a major toxic
    chemical.The ozone study is just one of a number of fascinating
    outcomes from the Tara expedition. The boat was originally owned by a
    private French company but was donated to the European research

    The 36m, 130-tonne boat is currently locked in ice
    The schooner provides habitation for about 10 people
    Scientists deploy and monitor a number of instruments
    Experiments study air, ice and ocean behaviour
    is a key project in Damocles (Developing Arctic Modelling and Observing
    Capabilities for Long-term Environmental Studies), a European-led
    effort to gather much needed new information on the changing Arctic.The
    two-masted vessel was sailed into the pack-ice in September 2006 and
    allowed to drift with the ocean currents and wind – but it has moved
    further, faster than anyone expected.”The boat is full of sensors to
    monitor the ocean, the atmosphere and the ice. It also serves as a
    logistics platform for Damocles to put observational beacons all around
    the Arctic,” explained Christian de Marliave, Tara’s scientific
    director.”When you are on a boat at least you are floating. This is a
    big security. More and more I think, it will be a ship that will be
    used as an ice camp. It’s become very dangerous. This year, the
    Russians were unable to find ice thick enough to place their camps.”

    Quick release
    is approaching the edge of the pack-ice and is likely to emerge into
    the open ocean between Greenland and Svalbard in the next few
    weeks.With just over half of International Polar Year (IPY) still left
    to run, Tara is likely to be sent to the Bering Strait to study how
    warm waters from the Pacific are entering the Arctic Ocean and
    contributing to ice shrinkage.Dr Dave Carlson, the director of IPY,
    said the Tara platform had provided many remarkable insights during its
    15-month drift.He has been taken by its observations of “frazil
    ice”.”We think of ice as forming at the interface of ocean and
    atmosphere, but Tara has seen a lot of this ice that foams 20m down and
    then floats up to the surface.”You can think of it as a reverse
    snowfall – crystals that form at depth and then make their way to the
    surface because of their density. It tells us the layers in the ocean
    don’t work in quite the way we thought they did.”