On February 25, 2009, there will be a celebration in Geneva, Switzerland to officially close the 4th IPY that started on March 1, 2007 in Paris, France. It is not a surprise that one of the main topics of this 4th IPY was climate change, since the polar regions play a very important role in Earth’s climate. This role is magnified by the combined effect of two main processes: one is due to the presence of greenhouse gases in the atmosphere trapping longwave solar radiation, which keeps our atmosphere warm, and the other, called albedo, is due to the capacity of the Earth’s surface to either reflect (in particular over ice and snow) or absorb (in particular over the ocean) incoming shortwave solar radiation.

Unprecedented events have been reported during the past 20 years in the Arctic Ocean, mostly related to the Arctic sea ice summer minimum extent that retreated in September 2007, far beyond previous extreme minimum records. This is the first clear evidence of a phenomenon of importance on a planetary scale, forced by global warming, mainly caused initially by an Earth energy imbalance due to greenhouse gas concentrations increasing in the atmosphere.

The Earth now absorbs 0.85 watts per square meter more energy from the sun than it emits into space, raising the likelihood of an acceleration of sea ice melting, ice sheet disintegration and a rise in sea levels (Hansen et al. 2005).

The European integrated project Damocles is one of the major programs of the International Polar Year (2007-2009). It is dedicated to the Development of Arctic Modelling and Observing Capabilities for Long-term Environmental Studies (DAMOCLES). Damocles started in December 2005 and will end up in June 2010. Damocles was proposed and selected by the European Union in response for a call addressing the development of observing systems for predicting extreme climate events.

Damocles was based on the fact that Arctic sea ice was retreating and thinning at an alarming pace. Projecting a disappearance of Arctic sea ice during summer in the near future could be considered as an extreme climate event. During the two international polar years 2007 and 2008, Damocles experienced two extreme climate events. Arctic sea ice retreated during both IPY years by more than 1 million km2 compare to a previous extreme case occurring in September 2005 before Damocles and IPY started.

It is quite instructive to compare the last three years (2005, 2007 and 2008) and also to compare the past 20 to 30 years, when satellites for observing planet Earth have been in existence.

Over the past 30 years we have observed a gradual long-term warming, mostly characterized by milder winter freezing seasons and longer summer melting seasons, evidencing strong albedo positive feedback effects. Less ice means more sea water being exposed to short-wave solar radiation that would be absorbed and transformed into heat by the ocean melting more ice and so on. Strong positive feedback accelerates the melting of Arctic sea-ice, especially due to the sharp contrast of the high albedo for sea-ice areas covered with snow (>0.8) that reflects 80% of the incoming solar radiation back into space, in contrast with the very low albedo (0.2) of the ocean, absorbing 80% of the incoming solar radiation.

Although long-wave and short-wave downwards solar radiation agreed rather well between models and observations, one of the biggest uncertainties in Arctic climate simulations still remains how albedo effects are affected by cloud cover and aerosols (Arctic haze). Warming amplification in the Arctic resulting in sea-ice thinning and retreat might also be attributed partly to atmospheric circulation (Graversen et al. 2008) and oceanic circulation (Zhang et al. 1998, Polyakov et al. 2005 and Dmitrenko et al. 2008) but this is still controversial. A drastic retreat of the sea-ice minimum extent in summer has inevitably profound consequences during the following fall season. Then all the heat taken up by the ocean has to be evacuated by the atmosphere, delaying the onset of freezing and consequently the amount of sea ice formed during the following winter. Observations taken during the past 20 years indicate that sea ice is becoming thinner, younger, moves faster and retreats more and more in summer. The sea-ice extent, ice thickness, ice drift and ice age are all interrelated parameters best characterizing Arctic sea-ice evolution and it is remarkable to realize that all these parameters have changed radically.

Surprisingly, the 2007 Arctic sea-ice event was largely unpredicted, even if extreme sea-ice conditions were observed almost every September month each year over the past 10 years (Perovich et al. 1999, 2003, Serreze et al. 2003 and Stroeve et al. 2005). Premises for an Arctic sea-ice thinning and of an Arctic ocean warming were reported nearly 20 years ago by Wadhams (1990) and Quadfasel (1991). So why the 2007 Arctic summer sea-ice minimum extent occur as a complete surprise if it was not an exceptional and an extraordinary event?

During the summer of 2005 we did not observe any replenishment of the MYI (Multi Year Ice) lost during the previous months by FYI (First Year Ice) either because FYI melted entirely or because FYI escaped the Arctic Ocean through Fram Strait or both. So at the end of the summer of 2005, there was almost no FYI left and consequently second year ice could not grow. Only MYI remained in the Arctic Ocean in 2005 and that explained why an extreme Arctic sea-ice extent minimum was reached during that particular year.

During the summer of 2007 we observed a similar situation but even more extreme simply due to a cumulative effect characterized by no replenishment of MYI by FYI during previous years. That explained why MYI was so depleted, leading to an extreme situation in September 2007 with an all-time absolute sea-ice extent record minimum. It is quite important to understand precisely why in 2005 and 2007 all FYI disappeared and could not replenish any of the MYI like it usually did in normal years. There are several potential reasons such as a polar amplification of global warming in particular in summer during the melting season due to strong albedo positive feedback.

During the summer of 2008 we observed a drastic decrease of the Arctic MYI and an exceptional replenishment of MYI by FYI. Because FYI resisted the summer melt in 2008, the sea-ice extent minimum record of 2007 was not reached in 2008. It would be quite important to understand precisely why FYI in summer 2008 resisted both the summer melt and the transpolar drift through Fram Strait.

Based on the 2005, 2007 and 2008 extreme events occurring in the Arctic and on observations occurring very intensively thanks to the IPY stimulus and the Damocles project, it is remarkable that scientists collected lots of basic information badly needed for improving modelling and predictive capabilities. At the same time however, it should be recognized that the situations met both in 2007 and 2008 were entirely unpredicted by the IPCC models. The original design proposed by the Damocles consortium to the European Commission had to be completely revised and adapted to the new situation.

The first polar year of Damocles (2007) was mainly characterized and highlighted by the transpolar drift of the French vessel Tara (September 2006-January 2008), 115 years after the Norwegian Fram expedition with Fridtjof Nansen at the helm. Tara drifted along the transpolar drift in an amazing 15 months (500 days) compared to 3 years for the Fram 115 years ago.

During the exceptional summer of 2007, the Russian icebreaker Akademik Fedorov from the Arctic and Antarctic Research Institute (AARI) based in Saint Petersburg (Russia) and the German icebreaker Polarstern (the SPACE project) from the Alfred Wegener Institute (AWI) based in Bremerhaven (Germany), circumnavigated an Arctic Ocean drastically depleted with sea ice, collecting an abundant dataset to document the prevailing conditions met during this peculiar summer of 2007. Akademik Fedorov deployed the NP35 Russian drifting station in September 2007 during the very last day of the campaign, near the Svernaya Zemlya Russian islands. NP 35 was recovered near Svalbard 10 months later, confirming the acceleration of the transpolar drift as also observed by Tara.

The second polar year of Damocles (2008) was highlighted by an impressive number of field work campaigns involving seven icebreakers from Russia (Akademik Fedorov and Kapitan Dranitsyn), from China (Xuelong), from Sweden (Oden), from Germany (Polarstern), from Norway (KV Svalbard and Lance) and from Canada (Louis Saint Laurent). The Swedish icebreaker Oden was stationary in the vicinity of the North Pole during the whole summer of 2008 (the ASCOS experiment).

New important processes were discovered during winter and summer of 2007 and 2008, such as frazil ice formation (deep ice) during the transpolar drift of Tara in winter, as well as ponds melting throughout the entire layer of ice, which drastically accelerated lateral sea-ice melting, as observed from the Chinese icebreaker Xuelong during summer of 2008.

Very innovative high technology was operated during Damocles, such as ITP, POPS, MOPS, AITP and sea glider, and an impressive array for acoustic tomography in Fram Strait was deployed. All kinds of new systems for performing sea-ice thickness measurements such as EM bird, ULS on floats and submarines, tiltmeters and seismometers and IMBs were operated.

An important September Sea-Ice Outlook was initiated by the Search for Damocles group in April 2008 after an S4D workshop organized in the US (Palisades, New Jersey) in March 2008. This Outlook will continue in 2009. A new workshop will be organized in Boulder, Colorado, in March 2009. The S4D activities were pretty successful in 2008, as illustrated by the five workshops organised during that year.

Damocles stimulated a very intensive international cooperation with the US, thanks to an EU initiative (Search for Damocles); with the Russian Federation, thanks to the EU initiative Damocles TTC (Third Targeted Countries) extension; with China thanks to a Memorandum of Understanding signed with the PRIC (Polar Research Institute of China) in Shanghai to participate in the Arctic Chinese expedition Chinare 2008 on board the Chinese icebreaker Xuelong; and with Canada thanks to a convention signed with the PCSP (Polar Continental Shelf Project) to access the Canadian Polar stations of Resolute Bay and Eureka (Environment Canada).

Our main conclusions so far indicates that there is a very low probability that Arctic sea ice will ever recover. As predicted by all IPCC models, Arctic sea ice is more likely to disappear in summer in the near future. However it seems like this is going to happen much sooner than models predicted, as pointed out by recent observations and data reanalysis undertaken during IPY and the Damocles Integrated Project. The entire Arctic system is evolving to a new super interglacial stage seasonally ice free, and this will have profound consequences for all the elements of the Arctic cryosphere, marine and terrestrial ecosystems and human activities. Both the atmosphere and the ocean circulation and stratification (ventilation) will also be affected.

This raises a critical set of issues, with many important implications potentially able to speed up melting of the Greenland ice sheet, accelerating the rise in sea levels and slowing down the world ocean conveyor belt (THC). That would also have a lot of consequences on the ocean carbon sink (Bates et al. 2006) and ocean acidification. Permafrost melting could also accelerate during rapid Arctic sea-ice loss due to an amplification of Arctic land warming 3.5 times greater than secular 21st century climate trends, as pointed out recently by Lawrence et al. (2008). This permafrost evolution would have important consequences and strong impacts on large carbon reservoirs and methane releases, either in the ocean and/or on land.

There will be a large symposium organised in Brussels on November 17-19, 2009 by the Damocles consortium to present the complete and final results.

Recommendations

1. Establishment of an Arctic Treaty covering scientific needs, rights and access for exploring the Arctic in exchange of a fully transparent process for all scientific activities occurring under the Treaty, including unlimited and full transparent data sharing between all the parties.

2. Large European involvement for Arctic exploration: promotion of the Aurora Borealis European icebreaker and European full partnership in the Arctic Council.

3. Establishment of an international pan-Arctic coordinated scientific network of polar stations including Tiksi (Siberia), Resolute Bay & Eureka (Nunavut), Longyearbyen & Ny Alesund (Svalbard), Nuuk (Greenland) and Point Barrow (Alaska) and logistical platforms (ice breakers).

4. Establishment of an international pan-Arctic coordinated scientific network of Arctic researchers gathering ALL scientists working in ALL countries contributing to Arctic research with NO exclusion. This network (Open Forum) should elaborate and keep updated a coordinated science plan for future Arctic research covering all disciplines. Scientists should elect network coordinators for any given stretch of time. This network should also elaborate an implementation plan to be discussed with national and international polar agencies. The European Union and the Arctic Council could provide the funding necessary for the foundation and functioning of this international network of scientists. That would be a great legacy of both IPY and Damocles.

5. The fourth IPY is ending soon but due to the rapid evolution of climate change, specially in the Arctic domain, we need to maintain a high level of scientific activity in the Arctic. It would make no sense to wait for another 50 years for the fifth International Polar Year to continue our investigations regarding climate change.

6. The human dimension of climate changes is global and this is why we called the new era the anthropocene.

Source: ipy