Geoscience Reference
In-Depth Information
to 14 mm in July (Serreze, Barry, and Walsh, 1995a ). This compares to a global
mean annual average of about 25 mm. Approximately 80 percent of the total water
vapor in all months is concentrated between the surface and 700 hPa and 95 is per-
cent below 500 hPa. During the summer half-year, the spatial pattern of precipitable
water is primarily a function of latitude, whereas there is greater asymmetry in the
winter half-year. Amounts are least over the Canadian sector and largest over the
Norwegian Sea as a result of patterns of evaporation, the planetary wave structure,
and associated vapor transports by synoptic-scale eddies. On average, the strongest
moisture transports into the Arctic tend to be found near the prime meridian in asso-
ciation with the North Atlantic cyclone track ( Chapter 6 ). As shown by J. Gyakum
( 2000 ), moisture transports associated with significant precipitation events over the
Arctic drainage basins are often organized into well-defined “tropospheric rivers”
(Zhu and Newell, 1998 ).
2.3.5
Aerosols and their Climate Effects
Aerosols (small liquid or solid particles in the air of either natural or anthropogenic
origin) play a major yet still incompletely understood role in Arctic climate through
their direct effects on scattering and absorbtion of solar radiation, through indirect
effects by their influence on cloud albedo and lifetime, and, through aerosol depo-
sition (soot on snow), the surface albedo. Natural aerosols include sea salt, dust and
pollen, sulfate from volcanic eruptions, and black carbon from biomass burning.
Anthropogenic aerosols include sulfate and black carbon from fossil fuel burning
and other products from industrial activities.
Arctic explorers of the nineteenth century were surprised by the peculiar haze
that could sometimes limit visibility. As reviewed by T. Garrett and L. Verzella
( 2008 ), the first formal recognition of what we now call Arctic haze can be traced
to a paper published in Science by the Swedish geologist Erik Nordenskiold, who
also remarked on “kryokonite,” a thin, dark layer distributed over ice that con-
tained not only microscopic plants, but metallic iron, cobalt, and nickel. Although
Nordenskiold attributed the mineral content to the deposition of cosmic dust, what
he was actually looking at was the deposition of airborne particulates associated
with smelting and coal combustion in industrial regions lying to the south. Fridjof
Nansen came to this basic conclusion in 1882 after an evaluation of “ice dust”
collected along the southeast coast of Greenland. Only much later did J. Mitchell
( 1957 ) draw widespread attention to the Arctic haze phenomenon on the basis of
observations during the U.S. Air Force “Ptarmigan” series of aircraft weather recon-
naissance missions.
As is now known, Arctic haze, which has seasonal peaks in late winter and
spring, is attributed to soot, dust, and sulfate aerosols emitted by industrial com-
plexes, especially those in northern Eurasia, which are then transported into the
Arctic. Industrial plants in northern Russia located in the Kola Peninsula, Norilsk
(nickel-copper smelting) and oil and gas exploitation in the Tyumen area, are all
chemically identifiable sources within the Arctic Circle (Harris and Kahl, 1994 ).
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