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https://theconversation.com/antarcticas-sea-ice-is-changing-and-so-is-a-vital-part-of-the-marine-food-web-that-lives-within-it-255606>
"Antarctica is the world’s great cooling unit. This vital part of Earth’s
climate system is largely powered by the annual freeze and melt of millions of
square kilometres of sea ice around the continent.
Our research shows changes to this annual freeze cycle in McMurdo Sound can
lead to shifts in the diversity of algal communities that live within the sea
ice.
At the start of the southern winter, as sea water begins to freeze, it expels
salt and forms heavy and very cold brine. This sinks to the seafloor,
ultimately forming what’s known as Antarctic Bottom Water. This is then pumped
out to the rest of the world through several major oceanic currents.
Historically, this cycle meant that Antarctica effectively doubled in size and
the continent was surrounded by an enormous apron of sea ice at the peak of
winter. But the changing climate is shifting this annual cycle.
For the past decade, Antarctic sea ice has been in decline. It hasn’t been a
steady trend, but each year since 2016 less sea ice has formed compared to
historic averages.
Antarctica’s annual maximum sea ice extent in September 2023 was the lowest on
record, with approximately 1.75 million square kilometres less sea ice than
normal – an area equivalent to about 6.5 times the land area of Aotearoa.
Change happening at the continental scale is usually well documented and
publicised. However, smaller, more local changes are also occurring in places
such as McMurdo Sound, the home of Aotearoa New Zealand’s only Antarctic
outpost.
For four of the last seven years, unseasonable winter southerly storms have
been associated with significant delays in the timing of sea-ice formation
within McMurdo Sound.
Where measurements were taken during these “unusual” years, the sea ice that
formed later was thinner (1.5 metres compared to 2.5 metres) and had less snow
cover (about 5 centimetres versus 15-30 centimetres) compared to the same
locations during “typical” years."
Cheers,
*** Xanni ***
--
mailto:xanni@xanadu.net Andrew Pam
http://xanadu.com.au/ Chief Scientist, Xanadu
https://glasswings.com.au/ Partner, Glass Wings
https://sericyb.com.au/ Manager, Serious Cybernetics
