ARCSS Program | Changing Seasonality
Changing Seasonality in the Arctic
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.