Polar bear populations have declined by 40 per cent in a decade in the Beaufort Sea region north of Alaska. Photo: Flickr.com / Naql CC BY
The Cry of the Cryosphere
Summer snow cover in the Arctic has decreased by 2.5 million km2 in fifty years. The changes for animals and human livelihoods in the affected regions are dramatic.
Since we realised the dangers of climate change, the frozen parts of our planet have been at the heart of concerns regarding the impacts of temperature rise. The glaciers, as well as ice and snow cover, form very visible targets for these impacts, and of course the effects of temperature are very direct and easy to understand. The cryosphere is to a large extent also home to important and vulnerable organisms and ecosystems that cannot survive anywhere else. Some of these species, such as polar bears, have even become the very symbol of climate change.
The recent special report by the IPCC on the Oceans and Cryosphere1 (SROCC) and its summary for policymakers unfortunately corroborates and deepens the concerns. The effects already observed include the loss of mass from ice sheets and glaciers, as well as effects on snow cover and Arctic sea ice, together with record-high permafrost temperatures.
The scale of effects is in many cases enormous, as exemplified by mass losses averaging 278 and 155 Gt annually (2006–2015) for the Greenland and Antarctic ice sheets, respectively. The loss of June snow cover in the Arctic land areas translates into the staggering figure of 2.5 million km2 between 1967 and 2018.
The physical changes also have impacts on species and biodiversity, including decreased habitats for plants adapted to cold and/or snow in high mountain areas, and for mammals and birds associated with ice in polar regions. The poster symbols for climate change – the polar bears – are among the unfortunate losers in the battle against rising temperatures. In 2019, the second-lowest annual minimum on record was reported for Arctic sea ice2, leading to drastically impaired feeding conditions for the polar bears. Not surprisingly, dramatic declines in polar bear populations have already been observed in some regions, such as the Beaufort Sea, where the population has been reduced by 40 per cent in a decade (Steven Amstrup, Polar Bears International, in citation above). The effect on polar bears sometimes also hits the headlines in a dramatic fashion, as the animals are forced to migrate: In February 2019, 52 polar bears were reported to have invaded the town of Belushya Guba in Russia3!
Naturally, as conditions change, the implications do however vary for different species. Whereas many species lose habitats, some species also benefit and can expand their range by migrating to new areas. An obvious example is the upward migration of lower-elevation mountain species. Changes in biodiversity are the ultimate outcome of the loss of ground for many species and the expansion of others, and from a conservation perspective these changes are clearly seen as negative.
Livelihoods are also affected, as exemplified by negative effects on agriculture in the Himalayas and tropical Andes, and changing conditions for people in Arctic regions, including indigenous people. The negative impacts also include reduced food and water security. The specific livelihoods affected, in addition to agriculture, are fishing, gathering, herding and hunting. As many of these are also important for cultural identity and/or tourism, it is evident that the societal and economic consequences are vast.
Projections of further change indicate that unavoidable future effects on glacier mass, permafrost, snow cover and Arctic ice cover will occur towards 2050 under all emission scenarios. However, if greenhouse gas emissions are drastically cut, there is a chance to reduce effects beyond 2050. Nevertheless, the projections show that negative effects on nature and humans exemplified above will continue. It is vital, though, to grasp the chance to dampen the effects through rapid measures against greenhouse gas emissions.
These pessimistic projections are unfortunately supported by recent events and reports. For instance, the Greenland ice sheet lost more than 12.5 billion tons in one day during this very summer. Or, as put in perspective in a Tweet by climate scientist Martin Stendel when the melting took place: “…The amount of ice that melted from the surface of the ice sheet just during the last two days would be enough to cover #Florida with almost five inches of water.”
Apart from direct effects on plants, animals, people and livelihoods in affected regions, there are also significant feedback mechanisms between the cryosphere and other systems. For instance, the global mean sea level has exhibited an accelerated rise because of ice loss in Greenland and in Antarctica. The rise since 1902 was already 0.16 m in 2015, and the annual rise of 3.6 mm between 2006 and 2015 is said to be unprecedented in the last century. Accelerated effects on Antarctic ice may lead to sea-level rise of several metres over a longer term (centuries) and, although there is uncertainty in projections, there could be an onset of irreversible instability in these ice sheets.
Furthermore, sea ice loss contributes to increased wave heights, whereas the runoff of rivers is impacted in mountain basins dependent on snow or glaciers. This last effect is reportedly independent of emission scenario. Rises in permafrost temperature, which have already reached record-high levels, are projected to potentially lead to the release of enormous amounts (tens to hundreds of billions tons) of CO2 and methane, which would of course further accelerate climate change in a very dramatic fashion.
The IPCC’s work will continue with the preparation of the 6th assessment report. In the meantime, the work of the IPCC, civil society and increasingly the general public (not least driven by a younger generation and “the Greta effect”) has already led to more and more pressure on politics nationally and internationally. The dramatic effects on the cryosphere, and their consequences for species, biodiversity and livelihoods, together with feedbacks on other systems driving climate and oceanographic processes, should and must make a strong argument for rapid action to strongly reduce emissions of greenhouse gases. The report is timely for the upcoming COP25 and for the EU’s Green Deal, and the National Energy and Climate Plans as well as the National Long Term Strategies of the EU member states. The summary for policy makers should be an important publication to study for all governments and their representatives.
The SROCC also points to areas where scientific evidence still needs to be strengthened. Many of these areas concern large-scale processes with potentially extremely important global consequences. These processes include the release of CO2 and methane from permafrost, the possible onset of irreversible ice sheet instability, and long-term projections on the effects of melting ice on sea level rise. It is in the interests of both civil society and concerned governments that science gets the necessary support to conduct vital studies on these subjects, and that the results can be incorporated in future work by the IPCC and civil society.
1 Special Report on the Ocean and Cryosphere in a Changing Climate, 2019
2 See e.g. https://www.theguardian.com/world/2019/sep/29/polar-bears-arctic-sea-ice...