Geoscience Reference
In-Depth Information
equivalent during April and May is approximately 100-110 mm. Locally, the snow
depth also depends on the ice age; when a lead forms in the ice in winter, new ice
growth takes place. The snow then accumulates on the surface of the new ice from
snowfall and drifting.
2.3.2
Snowline Altitude
The average climatic snowline is the elevation above which snow will survive the
summer melt season. It is indicative of both snowfall and SAT, the latter especially
in summer. It is around 1,200-1,400 m in Iceland and 700-900 m in Jan Mayen,
decreasing northeastward. In Svalbard, it is only 200 m in western coastal regions,
rising inland to 800 m (Koryakin,
1990
). On Novaya Zemlya, it decreases from
400-600 m on the western, Barents Sea coast to 200-300 m on the eastern Kara Sea
coast. On Severnaya Zemlya the snowline lies between 400 and 600 m, compared to
Franz Josef Archipelago where it is about 250 m and on De Long Island in the New
Siberian Islands where it lies at 300 m.
2.3.3
Temperature
I.G. Rigor, R.L. Colony, and S. Martin, (
2000
) compiled maps of mean Arctic SAT
based on blending data from coastal and inland stations with Arctic Ocean mea-
surement from the NP stations and from the IABP. Since 1979, the IABP has main-
tained arrays of drifting buoys over the Arctic Ocean to provide records of surface
pressure, ice drift, and SAT (see also
Chapter 1
,
Section 1.3
). As is evident from
Figure 2.24
, the annual cycle of SAT varies dramatically between inland continental
sites and maritime and coastal regions.
Temperatures drop below the freezing point during the second half of August
over most of the Arctic Ocean and by mid-September along the Arctic coast from
Taymyr eastward to 120°W. January means near the North Pole are −32° to −33°C.
The lowest winter SATs in the Northern Hemisphere are recorded in northeast-
ern Siberia in association with the strong Siberian anticyclone (
Chapter 4
). Mean
values of below −40°C are found in January. Locally (and not evident on the scale
of
Figure 2.24
), topographic effects play a major role. “Cold air lakes” form dur-
ing winter in basins and valleys. Verkhoyansk, located along the Yana River at
67°N, is notorious for its winter low temperatures. A. Hastings (
1961
) indicates
that 60-70 percent of observed SATs here in January are below −40°C and mean
annual minimum values of −62°C are recorded. In the lowlands west and southwest
of Great Bear Lake, there is a corresponding area in which mean annual minima
are −48°C or below. Despite the record low of −63°C recorded at Snag (62°N,
140°W) in the Yukon, there is a higher frequency of temperature readings below
−40°C recorded at Eureka in Ellesmere Island. Also, based on the records during
1957-1958 at Lake Hazen, the interior valleys of Ellesmere Island may experience
the longest periods of readings below −40°C in North America, as a result of the
very light winds (Jackson,
1959a
).
