The Arctic coasts have been eroding at elevated rates in recent years. Carbon pools in the permafrost regions are vast reservoirs that are extremely vulnerable to the impacts of climate change. Thawing permafrost, coupled with an increase in sea levels, further exacerbates coastal erosion and amplifies global warming. While the rates of erosion vary from place to place, an increase in the frequency of extreme events can lead to 30-40m of coastlines eroded every year. Here’s how climate change leads to coastal erosion in the Arctic and the catastrophic consequences of this phenomenon on the environment.
What is the Arctic Permafrost?
The Arctic and sub-Arctic regions store large quantities of organic carbon and ground ice – collectively termed permafrost. These perennially frozen landscapes generally remain well-protected during the winters, when sea ice temperature is below freezing point, thereby keeping the soils frozen and stable. During the summers, the melting of sea ice and permafrost thawing destabilises these same landscapes. The cliffs and frozen ground become susceptible to rising open water periods, increased storminess, and wave heights. In addition to rising air temperatures, most of these factors have altered the Arctic coastal morphologies in the past decades, making them vulnerable to erosion and adversely affecting infrastructure and ecosystems.
Figure 1. Coastal erosion processes reveal the extent of underlying ice-rich permafrost in the Arctic Coastal Plain in the Teshekpuk Lake Special Area of the National Petroleum Reserve (Alaska) – Photo by Brandt Meixell, USGS
How does Arctic Coastal Erosion Contribute to Global Warming?
The high-latitude regions of the Earth have been experiencing amplified warming, with temperatures increasing around 0.6C every decade over the last thirty years, which is twice as fast as the global average. The permafrost zones in the north absorb organic carbon and are estimated to store about 1,700 billion tons. In recent decades, studies have suggested that carbon storage in the Arctic and sub-Arctic regions goes as deep as 3 metres (9.8 feet) into the soil, well below the traditional zone of carbon accounting. This is because, in the past, deeper measurements were generally rare and there were several uncertainties surrounding the estimation of this carbon pool.
Permafrost carbon in the soils provides the basis for greenhouse gases to release into the atmosphere, but the rate and magnitude at which this happens is controlled by the overall decomposability of the organic carbon. Among the factors which control the decomposability of these cold soils are the concentration of oxygen saturated in the soils and sediment accumulations, particularly in permafrost regions characterised by wetlands, lakes, and waterlogged soils.
Figure 2. The Permafrost Carbon Feedback is an amplification of surface warming due to the thaw of organic material present in permafrost soils, which decay over time and release carbon dioxide and methane into the atmosphere. Photo retrieved on IOPscience.
Upon thawing of permafrost, organic matter and carbon undergo microbial decomposition, a process through which greenhouse gases like carbon dioxide and methane are released into the atmosphere. This feedback further amplifies global warming, leading to environmental and economic consequences. Now the critical question here is: At what rate does this take place?
The answer depends on the degree of climate change on decadal to century-timescales and the spatial variation across the landscape, which refers to aerobic or anaerobic activity and the amount of carbon and ice present in the soils. Most of the direct emissions come from thaw slumps onshore. Abrupt collapses of frozen blocks from steep coastal cliffs into the ocean are also common, and this can exaggerate the release of carbon dioxide. Furthermore, near-shore ocean dynamics also play a role in the degradation of organic matter. In the event of abrupt thawing and coastal erosion, the organic carbon is released into the oceans and remains suspended in the water column. This permafrost carbon released into the nearshore zones undergoes one of many processes: it can deposit in marine sediments, be transported offshore by winds and waves and undergo mineralization or it can potentially spread in the atmosphere in the form of greenhouse gases. Mineralization and transport can further enhance climate warming effects, facilitating a positive carbon feedback.
In addition to the questionable fate of eroded carbon in these regions, climate change impacts are still projected to cause further problems in the future. By the middle of the 21st century, the Arctic is most likely to be totally ice-free during summer. While smaller sea-ice covers mean increase in productivity, there is still an uncertainty that looms over the nutrient availability in the Arctic. At the same time, warmer and fresher Arctic waters may reduce the carbon dioxide uptake activity. Hence, this modest balance between these processes can determine the net-effect of future coastal erosion in the Arctic and can also help understand the carbon cycle.
Figure 3. A cabin in the Arctic Alaskan region seen washed into the ocean because the bluff on which it was built, was eroded away by rising sea levels. Photo by USGS.
The Future of the Arctic Carbon Cycle
A high proportion of residents in the Arctic live along the coastal zones and many derive their livelihood from terrestrial and coastal marine resources. Furthermore, the Arctic is itself a dynamic region of developments in industrial, commercial, tourist, and military sectors. Therefore, the socio-economic consequences of an extremely dynamic landscape will mostly become a recurring theme in the near to long term and will have a major influence on the decision-making and adaptation planning of the local governmental bodies.
For example, let’s look at the remote village of Yupik in Newton, Alaska, located in a highly variable permafrost zone along the Bering Sea. Newtok and another nearby village of Kivalina are estimated to go underwater in the next decade due to drastically high erosion rates along the low-lying cliffs areas which have resulted in relocation efforts in recent years. Federal, state, and local representatives have taken charge of prioritising the development of housing, energy, and an evacuation centre. Alaska’s Division of Community and Regional Affairs (DCRA) has introduced the Alaska Climate Change Impact Mitigation Program, which will look into hazard mapping assessments and community planning processes which also include relocation site feasibility studies.
In the Beaufort Sea region of Canada, another hamlet has a serious problem facing its shores. With increasing temperatures and rising sea levels, the Tuktoyaktuk community in North West Territories is facing extreme risks of coastal erosion. With reducing Arctic sea ice, larger areas of open water and waves are staying for longer periods relative to previous decades. The coastline is being eroded at rates of 2 metres (6.6 feet) per year and is at great risk of being breached in the next two decades, exposing the harbour to larger waves and intensified erosion. In 2020, the federal government announced US$5.5 million funding package for climate change adaptation strategies and clean energy projects in the area, $3.6 million of which will go into shoring up the coastline. Such activities involve the construction of more roads and installing of concrete mats along the shoreline. Scientists and research teams have also taken action to protect the coastline by cultivating local plant species in the form of vegetation mats which may combat permafrost by keeping the ground cold and intact.
Significant developments in satellite imagery and airborne platforms have led to more accurate, frequent, and extensive mapping of permafrost coasts due to the increase in spatial and temporal resolution of satellite data. More readily available data on sea ice, climate dynamics, and permafrost conditions have increased our capacity to better model and create future coastline movements and their impacts on infrastructure.
In recent years, the collaboration of several national and international scientific networks has enabled a better understanding of Arctic coastal dynamics. Our current dilemma has been focussed on environmental and social change, and with this lies a greater need for international collaboration between researchers, governments, local bodies, and societies to focus on permafrost coasts and Arctic coastal erosion in the years to come. Such developments certainly create a sense of hope and show promise for studying future changes in coastal permafrost dynamics and the influence on natural and built environments.
Featured Image by Benjamin Jones, USGS
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