Life in a cold environment - Antarctica: Global Science from a Frozen Continent - page 193

to or north of the oceanic Polar Frontal Zone. Further island groups are sometimes
included under the term

' '

, having some similarities in terms of biota
present and climatic regimes (Juan Fernandez, Falkland Islands, Gough Island,
Îles Amsterdam and St. Paul, New Zealand

sub-Antarctic

s outlying groups of Snares, Campbell,
Bounty, Auckland and Chatham) although they are more correctly described as
southern cool temperate or ocean temperate. While they do share many biological
similarities with the true sub-Antarctic islands, they also host faunal and

'

oral
groups not otherwise represented in the sub-Antarctic. All sub-Antarctic island
climates are strongly oceanic with mean air temperatures low and positive year
round, high precipitation and, except for South Georgia, they do not come under
the in uence of seasonal pack or fast ice.

The maritime Antarctic consists of a western coastal strip along the Antarctic
Peninsula, along with the Scotia Arc s South Shetland, South Orkney and South

Sandwich archipelagos, and the isolated Bouvetøya and Peter I Øya. Conditions are
more extreme, with mean temperatures slightly above 0 C for 1

'

4months of the
year, although like the sub-Antarctic they are buffered from extremes by the
surrounding ocean, which varies annually between c .

-

2 and +1 C at shallow
depths. Precipitation is, again, generally high. This region includes some unique
geothermal terrestrial ecosystems associated with volcanic activity on the South
Sandwich and South Shetland archipelagos and Bouvetøya.
The continental Antarctic is the third commonly recognised biological region.
Ostensibly encompassing a much greater area, it conventionally includes all East
(or Greater) Antarctica, the Balleny Islands, and the eastern side of the Antarctic
Peninsula. However, other than the Victoria Land Dry Valleys, the total area of
exposed terrestrial habitat is extremely limited. Conditions are again more extreme,
with positive mean air temperatures recorded for less than one month each year in
coastal locations and never inland. Away from the coast, air temperatures rarely
become positive even for short periods in the diurnal cycle in summer, although
absorption of solar energy by even small dark surfaces means that conditions at
the micro scale (appropriate to the biota) are less extreme in summer than the
standard meteorological records suggest.

Terrestrial biota

Other than on the sub-Antarctic islands, most terrestrial habitats experience
seasonal snow or ice cover, giving protection from temperature extremes and
wind abrasion. The duration of snow- or ice-free periods in summer varies widely,
from periods of days or weeks up to several months. Sub-Antarctic islands may only
have intermittent snow cover, and then often only at altitude. On these islands
microhabitat temperatures in soil or vegetation, with or without snow cover,