Geoscience Reference
In-Depth Information
are seeing this climate change signal is still unclear. Unresolved issues include the
strong asymmetry between discharge from Eurasia (increasing) and North America
(decreasing) and the relative importance of factors, such as changing forest fire
frequency. Most recent research has dismissed thawing ground ice as a significant
contributor to changing discharge. Reiterating statements in
Chapter 2
, assessing
changes in Arctic precipitation that ought to be related to altered discharge is made
very difficult because of the sparse observational network and other measurement
problems.
Focus Questions and Exercises
1) Precipitation over Arctic land areas tends to have a summer maximum and
winter minimum. We see the same seasonality in precipitation over the ice-
covered central Arctic Ocean. By comparison, precipitation over the northern
North Atlantic tends to have a cold-season maximum and summer minimum.
Explain these differences in the seasonality of precipitation.
2) Draw a monthly hydrographs for the Lena River at the point where it empties
into the Arctic Ocean. Label the axes. Draw a second hydrograph for the Lena
that you might expect to see in the year 2050. Explain the differences between
the two hydrographs.
3) Explain why the rate of evaporation over a melting sea ice cover in July will
be much lower than over an open lead in the sea ice cover in January.
