ARCSS Program | Changing Seasonality
Changing Seasonality in the Arctic
System
An Emerging Research Priority in the ARCSS
Program
Results from the ARCSS research community and others have clearly demonstrated that pervasive changes in the patterns of seasonality in the Arctic are underway. Recommendations from the ARCSS All-Hands Workshop in 2002 and recent community discussions, particularly those facilitated through the ARCSS Communities of Practice, have identified changing seasonality as an interdisciplinary and cross-cutting science uncertainty that addresses a key unknown in our ability to predict arctic system behavior.
The timing and dynamics of key events such as spring melt and fall freeze-up are shifting in response to a changing arctic climate―impacting the interconnected physical, biological, and human components and processes of the arctic system. The following are some examples of the importance of seasonal connectivity, which are plentiful and can be found throughout the arctic system:
As
spring snowmelt has shifted to earlier in the year,
plants have responded quickly and begun growing
earlier, but caribou calving has not kept pace. As
a result, when caribou need high quality forage,
the forage is already older and lower quality,
causing up to a 40% increase in early calf
mortality and as much as a 4-fold reduction in calf
production. The spring snowmelt represents a major
water input for the year and is also a time of high
soil nutrient availability; these have occurred
close to the peak in solar radiation input. As
snowmelt comes earlier, however, the availability
of nutrients, water, and light for plants may
become disconnected, potentially altering plant
community composition, its physical forcing back on
the climate (e.g., albedo differs between shrub and
sedge tundra), its effects on food chains and
humans, and on the quantity and nature of materials
(water and nutrients) transported to streams and
rivers.
A key feature of the arctic climate system is the
thermal contrast between the land and ocean that
produces the summer arctic frontal zone. Earlier
melting of sea ice and terrestrial snow may alter
this thermal contrast with consequent impacts on
coastal weather patterns and arctic ecosystems.
Altered freshwater inputs to the coastal ocean may
affect marine productivity and ocean
stratification. Changes in the relative timing of
terrestrial snowmelt versus sea ice melt may
strongly influence these important processes in
coastal ecosystems.
Earlier sea ice retreat is leading to large areas
of open ocean water in summer, which then warms by
absorbing solar energy. This shift in the timing
and amount of open water may affect the long-term
stability of the sea ice pack, the water mass
structure of the Arctic and global oceans, arctic
marine ecosystems, and human marine activities. For
example, when the sun rises, marine algae begin
actively photosynthesizing, and toxic ozone is
removed from the atmosphere by processes occurring
on the sea ice. Earlier ice loss may lead to
increased ozone supply to the ocean surface, with
impacts on marine primary productivity and food web
dynamics.
The opening of arctic waters may encourage
increasing industrial activities in the region.
Notably, however, the extent of summer sea ice may
be less important than the timing of landfast ice
formation in the autumn and break-up in the spring,
which are the factors that most strongly control
human activities—from local hunting to industrial
development and shipping. For example, winter is
the season for oil and mineral exploration, and
this season ends with the spring melt. Changes in
seasonality are widely identified by arctic
residents and others as of crucial importance for
human activities in the Arctic.