Arctic Climate Impact Assessment

(from AMSA Report 2009)

ACIA (Arctic Climate Impact Assessment), approved by the eight Arctic countries, was called for by the Arctic Council and the International Arctic Science Committee. The assessment found that the Arctic is extremely vulnerable to observed and projected climate change and its impacts.

The Arctic is now experiencing some of the most rapid and severe climate change on earth. During the 21st century, climate change is expected to accelerate, contributing to major physical, ecological, social and economic changes, many of which have already begun. Changes in Arctic climate will also affect the rest of the planet through increased global warming and rising sea levels. Of direct relevance to future Arctic marine activity, and to the AMSA, is that potentially accelerating Arctic sea ice retreat improves marine access throughout the Arctic Ocean.

The assessment confirmed, using a wealth of current Arctic research, that declining Arctic sea ice is a key climate change indicator. During the past five decades the observed extent of Arctic sea ice has declined in all seasons, with the most prominent retreat in summer. While the ACIA models have now been surpassed by more capable GCMs, each of the five GCMs used in the ACIA did project a continuous decline in Arctic sea ice coverage throughout the 21^st century (Map 2.3). From a strategic planning perspective, this is a key factor for evaluating future Arctic marine transport systems.

Map.2.3 Arctic sea ice simulations for the 21st century 

Source:Arctic Climate Impact Assesment

As noted previously, one of the models simulates a summer ice-free Arctic Ocean by 2050, a future scenario of great significance for Arctic shipping and offshore development. Such a physical occurrence would mean that multi-year ice could possibly disappear in the Arctic Ocean. All of the next winter’s ice would be first-year: no ice will have survived a winter season (and be able to gain strength and thickness).

GCM projections to 2100 suggest that in the summer the Arctic sea ice will retreat further and further away from most Arctic coasts, potentially increasing marine access and extending the season of navigation in nearly all Arctic regional seas. One critical limitation of the GCMs is that they are not useful for determining the state of sea ice in the Northwest Passage region. Their spatial resolution is much too coarse to be applied to the complicated geography of the Canadian Arctic Archipelago. In the ACIA, the only reliable observed data for the region comes from the Canadian Ice Service and this information, archived since the late 1960s, shows a mean negative trend of sea ice coverage in the Canadian Arctic, but very high year-to-year variability.

The ACIA models, however, could be applied very crudely to the more open coastal seas of the Russian Arctic. The ACIA sea ice projections for Russia’s Northern Sea Route indicated longer periods of ice-free conditions which could translate into a longer navigation season throughout the 21st century. The ACIA confirms that the observed retreat of Arctic sea ice is a real phenomenon. The GCM projections to 2100 show extensive open water areas during the summer around the Arctic basin. Thus, it is highly plausible there will be increasing regional marine access in all the Arctic coastal seas. However, the projections show only a modest decrease in winter Arctic sea ice coverage; there will always be an ice-covered Arctic Ocean in winter although the ice may be thinner and may contain a smaller fraction of multi-year ice.

The very high, inter-annual variability of observed sea ice in the Northwest Passage and non applicability of the GCMs to the region prevent an adequate assessment of this complex region. Although the ACIA projections indicate an increasing length of the navigation season for the Northern Sea Route (20-30 days per year in 2004, to 90-100 days by 2080), detailed quantification of this changing marine access also tested the limitations of the ACIA GCMs. Since the work of the ACIA, advances and refinements in the models may allow them to provide more robust strategic information on the length of time regions remain ice-free and year-to-year regional sea ice variabilities.

There is a definite need for improved Arctic regional models to adequately assess future changes in sea ice extent and thickness, and their considerable implications for expanded marine use of the Arctic Ocean. And, there is a significant need for more sea ice observations to improve the calibration and validation of the GCMs. The final ACIA report lists 10 major findings that are essentially the key impacts of climate change on Arctic people and the environment. The ACIA key finding #6 states, “Reduced sea ice is very likely to increase marine transport and access to resources.” One of the follow-on Arctic Council activities addressing this ACIA finding is the AMSA.

Arctic Council, 2009, Arctic Marine Shipping Assessment (AMSA), Arctic Council.©