164
B. STONEHOUSE
caption on p. 148. Temperature frequency curves emphasize the remarkably equable climates of the temperate and sub-Antarctic islands,
dominated by marine influences throughout the year and differing mainly
in the positioning of the cluster of curves along the temperature axis
(Fig. 8a, Campbell, Marion, Macquarie, Heard Islands). The Falklands
and Iles Kerguelen show slightly more varied seasonal climates with
wider temperature ranges; both groups being large enough to escape in
part the domination of marine influences, and to generate their own
climates. South Georgia, larger still, with a heavily glaciated alpine
spine, shows a bimodal temperature frequency distribution in autumn,
winter and spring. This probably reflects the conflicting influences of latitude (equivalent to the Falkland Islands’) on the one hand and proximity
to the northern edge of the pack ice on the other. Frequency curves for
the South Shetlands (Fig. Sb), and Argentine and Horseshoe Islands
(Fig. Sc), illustrate the progessive influence of increasing latitude on
autumn, winter and spring climate, with summers remaining almost
unaltered. The South Orkneys, although in lower latitude than the South
Shetlands, have a harder climate throughout the year because of the
cooling influence of the Weddell Sea drift (p. 154). The difference between
autumn-spring and summer climates increases a t coastal stations on the
continent (Figs. 8d and Se), and even at McMurdo Station in southern
McMurdo Sound there is a high frequency of summer temperatures close
to freezing point. This can be ascribed to the presence of bare rock (in
combination with high insolation) and several hundred miles of open sea
to the north a t the height of summer. Ellsworth, in a similar latitude at
the southern end of the Weddell Sea, is an ice shelf station from which
the pack ice is seldom far removed even at mid-summer; there are no
ameliorating influences of rock or open sea, and the climate is close to
that of stations in the interior of the continent.
Climate recorded under standard synoptic conditions by meteorologists differs in important detail €rom that surrounding animals close
to the ground or sheltered by rocks and vegetation. Wind at penguin
height may be only 10% to 20% of that recorded at standard heights of
2-6 m; and in still air temperatures may be higher (due to insolation) or
lower (due to outgoing radiation) than in a Stevenson screen. WXere
varied topography and vegetation provide a choice of habitats, animals
actively seek the situation and microclimate which best suits them, and
large animals modify it by their presence and activities. Thus tropical
penguins avoid strong insolation by burrowing or nesting in caves and
under vegetation. In polar and sub-polar regions, where vegetation is
sparse, the ground frozen or waterlogged and, in sheltered places, liable
to fill with drifted snow, penguins provide their own shelter by flocking
and nesting socially.
B. STONEHOUSE
caption on p. 148. Temperature frequency curves emphasize the remarkably equable climates of the temperate and sub-Antarctic islands,
dominated by marine influences throughout the year and differing mainly
in the positioning of the cluster of curves along the temperature axis
(Fig. 8a, Campbell, Marion, Macquarie, Heard Islands). The Falklands
and Iles Kerguelen show slightly more varied seasonal climates with
wider temperature ranges; both groups being large enough to escape in
part the domination of marine influences, and to generate their own
climates. South Georgia, larger still, with a heavily glaciated alpine
spine, shows a bimodal temperature frequency distribution in autumn,
winter and spring. This probably reflects the conflicting influences of latitude (equivalent to the Falkland Islands’) on the one hand and proximity
to the northern edge of the pack ice on the other. Frequency curves for
the South Shetlands (Fig. Sb), and Argentine and Horseshoe Islands
(Fig. Sc), illustrate the progessive influence of increasing latitude on
autumn, winter and spring climate, with summers remaining almost
unaltered. The South Orkneys, although in lower latitude than the South
Shetlands, have a harder climate throughout the year because of the
cooling influence of the Weddell Sea drift (p. 154). The difference between
autumn-spring and summer climates increases a t coastal stations on the
continent (Figs. 8d and Se), and even at McMurdo Station in southern
McMurdo Sound there is a high frequency of summer temperatures close
to freezing point. This can be ascribed to the presence of bare rock (in
combination with high insolation) and several hundred miles of open sea
to the north a t the height of summer. Ellsworth, in a similar latitude at
the southern end of the Weddell Sea, is an ice shelf station from which
the pack ice is seldom far removed even at mid-summer; there are no
ameliorating influences of rock or open sea, and the climate is close to
that of stations in the interior of the continent.
Climate recorded under standard synoptic conditions by meteorologists differs in important detail €rom that surrounding animals close
to the ground or sheltered by rocks and vegetation. Wind at penguin
height may be only 10% to 20% of that recorded at standard heights of
2-6 m; and in still air temperatures may be higher (due to insolation) or
lower (due to outgoing radiation) than in a Stevenson screen. WXere
varied topography and vegetation provide a choice of habitats, animals
actively seek the situation and microclimate which best suits them, and
large animals modify it by their presence and activities. Thus tropical
penguins avoid strong insolation by burrowing or nesting in caves and
under vegetation. In polar and sub-polar regions, where vegetation is
sparse, the ground frozen or waterlogged and, in sheltered places, liable
to fill with drifted snow, penguins provide their own shelter by flocking
and nesting socially.