Spring ozone hole may be one of the smallest for decades

Posted: September 17, 2019 by oldbrew in atmosphere, Natural Variation, ozone, weather
Tags:

Image credit: theozonehole.com


Southern hemisphere spring, that is.

European weather scientists believe the ozone hole over the Antarctic this spring may be one of the smallest since the mid-1980s, says stuff(NZ).

Experts at the Copernicus Atmosphere Monitoring Service (CAMS) have observed strange behaviours of the annual ozone hole this season.

Not only is it already shrinking and well on the way to being about half the size it usually is at this time of year, but also it began forming about two weeks earlier than usual and it is off-centre, away from the South Pole.

They say that is probably the result of the rare sudden stratospheric warming, which has been under way about 30km above Antarctica since last month.

Ozone in the stratosphere – the second tier of the atmosphere – absorbs the Sun’s damaging ultra-violet (UV) radiation. But ozone depletion causes a rise in UV radiation at the surface and a higher risk of skin cancers.

New Zealand has the highest skin cancer rate in the world, according to the Ministry of Health, with about 82,000 new skin cancers confirmed annually.

CAMS head Vincent-Henri Peuch​ said the Antarctic ozone hole typically started to form every year in August, reaching a maximum size in October and finally closing again in December.

“Since early September, the polar vortex which provides the conditions for ozone hole formation has been displaced off-centre and weakened by a sudden stratospheric warming event. With temperatures in the upper stratosphere rising up to 40 degrees Celsius above normal, the polar vortex has been more unstable than normal.”

Full report here.

Comments
  1. oldbrew says:

    No spare time to post this now, so putting it here…

    Wind-driven processes controlling oceanic heat delivery to the Amundsen Sea, Antarctica
    – by the British Antarctic Survey (BAS) — 10 September, 2019

    Variability in the heat delivery by Circumpolar Deep Water (CDW) is responsible for modulating the basal melting of the Amundsen Sea ice shelves. However, the mechanisms controlling the CDW inflow to the region’s continental shelf remain little understood. Here, a high-resolution regional model is used to assess the processes governing heat delivery to the Amundsen Sea. The key mechanisms are identified by decomposing CDW temperature variability into two components associated with (1) changes in the depth of isopycnals (heave; HVE), and (2) changes in the temperature of isopycnals (water mass property changes; WMP). In the Dotson-Getz trough, CDW temperature variability is primarily associated with WMP. The deeper thermocline and shallower shelf break hinder CDW access to that trough, and CDW inflow is regulated by the uplift of isopycnals at the shelf break – which is itself controlled by wind-driven variations in the speed of an undercurrent flowing eastward along the continental slope. In contrast, CDW temperature variability in the Pine Island-Thwaites trough is mainly linked to HVE. The shallower thermocline and deeper shelf break there permit CDW to persistently access the continental shelf. CDW temperature in the area responds to wind-driven modulation of the water mass’ on-shelf volume by changes in the rate of inflow across the shelf break and in Ekman pumping-induced vertical displacement of isopycnals within the shelf. The western and eastern Amundsen Sea thus represent distinct regimes, in which wind forcing governs CDW-mediated heat delivery via different dynamics.

    https://www.bas.ac.uk/data/our-data/publication/wind-driven-processes-controlling-oceanic-heat-delivery-to-the-amundsen-sea/

    https://doi.org/10.1175/JPO-D-19-0064.1

  2. ivan says:

    oldbrew, did they forget about all the volcanoes around Antarctica just might have something to do with the melt as well or don’t their models include real world things?

  3. oldbrew says:

    Re the ozone hole:
    Not only is it already shrinking and well on the way to being about half the size it usually is at this time of year, but also it began forming about two weeks earlier than usual and it is off-centre, away from the South Pole. [bold added]

    Does this – or, *how* does this – relate to the current deep solar minimum?

    Perhaps relevant:
    Xhao & Feng: Correlation between solar activity and the local temperature of Antarctica during the past 11,000 years
    Posted: October 4, 2015 by tallbloke

    https://tallbloke.wordpress.com/2015/10/04/xhao-feng-correlation-between-solar-activity-and-the-local-temperature-of-antarctica-during-the-past-11000-years/

  4. oldbrew says:

    Re SSW, see:
    ‘https://twitter.com/RARohde/status/1173905218221871109’

    WordPress won’t display the linked comment :/
    – – –
    From David Birch on Twitter @dbirch214…

  5. tom0mason says:

    The Sudden Stratospheric Warming look quite dramatic …
    At 10hPa (very high stratosphere)

    and at 30 hPa (low stratosphere)

    Images from http://ds.data.jma.go.jp/gmd/tcc/tcc/products/clisys/STRAT/index.html

  6. Brett Keane says:

    Of

  7. oldbrew says:

    ‘Scientists say that while losses started earlier than normal this year, they were truncated by a sudden warming event that lifted temperatures in the stratosphere by 20-30 degrees. This destabilised the ozone destroying process.’

    https://www.bbc.co.uk/news/science-environment-49714987

    How does a sudden stratospheric warming occur?
    https://www.metoffice.gov.uk/weather/learn-about/weather/types-of-weather/wind/sudden-stratospheric-warming

    Note the Met Office says SSWs are mostly a Northern Hemisphere phenomenon, the last Southern Hemisphere one being in 2002 – until this new one.