Even optimistic climate change predictions have periglacial zones at tipping point

About a quarter of the Earth''s land surface is made up of areas known as periglacial zones, which are found at the edges of glacial regions mainly in far northern and southern regions, as well as at high altitudes. These environments with frost-induced and permafrost-controlled land surfaces processes (LSPs) are vital for the cryosphere. However, researchers have recently concluded that, even based on the more optimistic estimates for future carbon emissions, periglacial zones will reduce substantially by 2050 and will be almost non-existent by 2100.

The study published in the journal Nature Communications points out that periglacial environments have already seen much change due to climate change such as glacier recession, shrub expansion to alpine tundra and alteration to permafrost thermal-hydrological regimes. Crucially, as well as impacting on landscapes and biodiversity, these ground condition changes can induce what is referred to as ‘climate feedback’. Here, dependent systems, such as ground surface reflectance (light reflected by snow and ice), can trigger processes that further amplify or diminish the effects of climate change.

Investigating the current and future periglacial climate

The scientists in this study, part funded by the EU’s HELIX (High-End cLimate Impacts and eXtremes) initiative, looked specifically at four periglacial zone processes. They worked with data which had been remotely sensed and field-quantified to an unprecedented scale, to investigate active surface features pertaining to cryoturbation, gelifluction, nivation and permafrost peat mounding across a high-latitude Fennoscandia region of ca. 78 000 km2.

The researchers contend that the absence of deep permafrost, unlike comparable regions such as the High Arctic Canada, will mean that changes to the LSPs are likely to be rapid. They point out that changes to this region are also reflective of likely changes to similar sensitive landscapes at high-latitude with areas of discontinuous and isolated permafrost, including large parts of Canada and Russia between 55 and 70° N latitudes. The team analysed the LSPs based on a modelling technique which used statistical algorithms to track the occurrence of climatic variables such as freezing and thawing degree days, water and snow precipitation, local topography and soil characteristics.

Once the climate baseline distributions had been established for the years 1981–2010, they developed climate projections of greenhouse gas concentrations based on three Representative Concentration Pathway (RCP) scenarios, over two time periods (2040–2069 and 2070–2099).

They concluded that there is likely to be a reduction in the current periglacial climate realm in the study area and that by the end of this century, active periglacial LSPs will exist only at high elevations. Most worryingly, team member Dr Juha Aalto, of the University of Helsinki and the Finnish Meteorological Institute says, ‘The results suggest that profound changes can be expected in current periglacial zones regardless of climate change mitigation policies.’

Speaking of the implications of the findings, Dr Aalto says, ‘Our results indicate significant changes in Northern European plant life. Many rare species can only be sustained in areas of intense frost activity or late-lying snow packs, so the disappearance of such unique environments will reduce biodiversity.’ This raises an important aspect to mitigation efforts, that of establishing realistic, evidence-based expectations.

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