Polar Regions: Key Sentinels for Climate Change
Discover the vital role of Earth's polar regions as sentinels for our climate future, exploring the profound environmental impacts of climate change on these crucial areas.
The Editors·
Discover the vital role of Earth's polar regions as sentinels for our climate future, exploring the profound environmental impacts of climate change on these crucial areas.
Listening to Polar regions. A Special Series by Global Geneva in media partnership with JONAA.
FOR CENTURIES, THE POLAR REGIONS were considered the most timeless, unchanging parts of the earth. A common belief was that they had little relevance to the ‘civilized’ world. Early European explorers created maps in the process of hunting for seals, whales and other marine life, and these were used for generations.
Arctic native peoples, however, were among the few who learned not only to survive, but how to thrive in their surroundings. There has never been an indigenous people occupying the Antarctic.
Today the Arctic people, scientists and governments realize that the assumed timeless stability of the polar regions is being rapidly disturbed as a consequence of human activity emanating almost solely from elsewhere on the planet. As someone who has led many expeditions throughout Antarctica, Greenland, and many other high and cold places, I consider myself truly privileged for the opportunity to experience these environments.
Standing on the high plateau in the centre of Antarctica, thousands of kilometres from civilization, I have been able to view, through the crystal-clear air, the curvature of the Earth, to breathe in the cleanest air on the planet, to drink Earth’s cleanest water (albeit after melting it in a tent in the midst of temperatures as low as -50 degrees C), and, when the wind stops, to hear my heart beat in my ears because there is no other noise. I have also felt the cold biting wind as it seemed to pass right through me as we ascended the last mountain before the South Pole, and spent many days tent-bound, waiting for storms to pass, surrounded by a world of swirling snow where companions’ voices can barely be heard and depth perception is replaced by just whiteness.
The effects of climate change on polar regions
The polar regions are still vast, largely unexplored, beautiful and treacherous, but we are now in the process of rapidly overpowering what we always thought were timeless landscapes as the following reveal:
• Arctic warming and sea-ice loss; permafrost degradation and collapse of coastlines creating infrastructure disruption and migration from heritage living areas;
• Arctic ecosystem upheaval resulting from overhunting, resource exploitation and increased human occupation;
• Antarctic and Arctic ozone depletion resulting in ecosystem exposure to solar radiation;
• Influx to the Arctic and Antarctic of:
– toxic substances, such as lead and sulphur, from industrial emissions resulting in increased levels of cancer, respiratory and neurological disease; and
– radioactivity from nuclear bomb testing, accidents and waste build-up causing significant health issues for humans and ecosystems.
• Weather extremes, such as drought, floods, storms, heat and cold waves, increasing in frequency and magnitude as a consequence of climate change in the polar regions.
The Arctic is an ocean fringed by land. The Antarctic, on the other hand, is an ice sheet surrounded by ocean. Seasonal sea ice one of the greatest seasonal events on the planet and Arctic sea ice is partially anchored by land, while the Antarctic’s extends seaward without terra firma anchoring. The difference from white snow and ice to dark ocean surface means, in its extremes, that most incoming solar radiation is reflected or absorbed. It is drawn in because of the absorbing nature of white and dark surfaces making the polar regions vast reflectors, and seasonal sea ice one of the greatest seasonal events on the planet.
Travelling across these highly reflective surfaces means a sunburn for any exposed skin in addition to windburn. Changes in the size and seasonal timing of these reflectors alter the distribution of temperature over the planet and the winds driven by these differences. In addition, when the ocean is covered by sea ice, even the relatively thin 1-3 metres common in the polar regions, heat is trapped in the ocean. Surface circulation is thus slowed by lack of contact with the wind that drives ocean waves. When sea-ice concentration declines, polar oceans release some of their trapped heat ‒ leading to “polar amplification”. This happens in reverse too, so that increased sea ice prevents heat being released from the ocean.
The Arctic-Antarctic geographic distinction is an essential underlying theme when considering three basic climate elements: surface temperature, atmospheric circulation, and sea-ice concentration that document polar climate change. As Figure 1 shows, there is a marked cold core for the Arctic centred over Greenland and another one over the Antarctic. The coldest near-surface temperatures are found over the highest portions of the Greenland and Antarctic ice sheets. Temperatures at these points are roughly -20 degrees C and -60 degrees C, respectively.
The Greenland ice sheet is approximately 1.7 million km2, 2400 km x 1100 km with a maximum thickness of roughly 3000 m. All of it rests on a continental substrate.
If melted completely, it would increase sea level by some seven metres. In contrast, Antarctic ice spreads across 14 million km2, some 5600 km x 4400 km with a maximum thickness of 4800 m. Melted completely, it would increase sea level by approximately 60m. The eastern part rests on continental substrate, while the western side facing South America lies on islands that are below sea level.
This makes at least the western side of the Antarctic ice sheet potentially less stable. It can float off more easily. Portions of West Antarctica, coastal Greenland and many mountain glaciers melted during the Eemian inter-glacial, the last naturally warm period lasting 130,000 to 115,000 years ago. Sea levels increased at this time by one to three metres in response to a temperature rise of 1 degree C to 2 degrees C. Forests reached into the Arctic circle and hippos swam in the Thames and Rhine rivers.
Recent temperature changes over the Arctic and Antarctic appear in Figure 2. Here we examine surface temperature changes by contrasting the 2000-2015 period with that of 1979-1999. During the more recent period the eastern Arctic warmed by up to 4 degrees C. This is equivalent to a doubling in the length of summer in this area. Closer scrutiny reveals that the warming happened in less than five years, making this potentially the first abrupt climate change of the modern era.
The Arctic temperature records also demonstrate that climate need not change slowly or steadily. In fact, we discovered from our research on past climate, using Greenland ice cores in the 1990s, that climate can change abruptly (in less than 1-5 years) under certain conditions, and now one of these conditions – greenhouse gas increase – is higher than anytime in at least the last 800,000 years and has grown at a significantly faster rate. Recognizing this potential for rapid transition in future climate predictions is essential if we are to develop plausible constructions of what is to come. In certain areas, climate change can be expected to proceed in abrupt jumps. With continued warming, release of carbon trapped in frozen ground in the Arctic increases this likelihood. Over the Antarctic there are notable areas of warming, associated with southward migration of warm mid-latitude air, and warm ocean currents affecting the Antarctic Peninsula, floating ice shelves and other coastal zones through southward migration of warm mid-latitude air, and warm ocean currents.
Scientific discussion of atmospheric circulation can be complex. One approach concerns zonal wind (the wind that runs along lines of latitude, where by definition positive (or negative) refers to winds that flow from west to east (or east to west) measured in metres per second at 850 mbar (approximately 1500m altitude) in the atmosphere.
The Southern Hemisphere westerlies flow around the Antarctic over the Southern Ocean, with their only continental constriction being the passage between South America and the Antarctic Peninsula. Arctic westerlies, on the other hand, are diverted in their flow by the continents surrounding the Arctic Ocean.
Recent changes in zonal winds are significantly associated with temperature change in the polar atmosphere. Over the Northern Hemisphere westerly winds have tended to weaken, largely in response to greenhouse gas-induced Arctic warming. This has resulted in a temperature decrease from the Arctic to the mid-latitudes and therefore a weakening of the barrier between cold Arctic air and warm air to the south. This in turn leads to tongues of cold air moving further south with warm air moving further north than usual.
GREATER WEATHER INSTABILITY: IT IS ALREADY CLEAR WHAT IS HAPPENING
This was particularly evident in the 30 December 2015 invasion of warm air that resulted in above-freezing temperatures at the North Pole (Figure 3).
Since then, the same thing has occurred again and will likely occur more frequently in the future. A weakening of this westerly wind barrier leads to more regions where cold and warm air collide, resulting in greater weather instability. This suggests a clear forecast for the Northern Hemisphere if not for global climate: greater instability.
As a result of greenhouse gas warming of the Southern Hemisphere mid-latitudes (Figure 4), westerly winds surrounding the Antarctic have contracted poleward like those in the Arctic, but around the Antarctic they have strengthened rather than weakened.
This is related to the temperature difference between the Antarctic and the mid-latitudes. There is some heat loss over the interior plateau associated with the human-induced Antarctic ozone hole because ozone traps some incoming solar radiation and, in combination with mid-latitude warming, this steepens the temperature difference, leading to an increase westerly wind speeds.
Cooling of surface waters over vast parts of the Southern Ocean (Figure 2) is a direct response to the rise in these zonal wind speeds that drive away surface waters to be replaced by deeper and colder water upwelling from below.
A major question is what will happen as the ozone hole heals over coming decades while greenhouse gas emissions continue to grow? Will this lead to stronger or weaker zonal winds? If weaker, or displaced even further south, warm air will penetrate farther inland over the ice sheet creating both increased melting and greater climate instability.
Changes in sea-ice concentration are in direct response to variations in surface temperature and winds. Arctic sea ice has decreased dramatically, due primarily to greenhouse gas-induced warming and the polar amplification associated with this loss of sea-ice. In contrast, Antarctic sea-ice has both decreased and increased. The former is associated primarily with the influx of warmer mid-latitude air and southward migration of more tepid ocean currents. The latter is a combination of strong zonal wind buffering (limiting warm air invasion from the north) and the intensification of shoreward-moving, katabatic(gravity-driven) winds. These are intensified by strengthened westerlies driven onto the Antarctic ice sheet. In turn, these cause the katabatic winds to increase, pushing sea ice further into the ocean, by breaking and opening gaps in the ice that freeze.
BOTH THE ARCTIC AND ANTARCTIC ARE CHANGING RAPIDLY – AND WITH DIRE CONSEQUENCES
The polar regions still offer many surprises and require significantly more scientific investigation. However, they are now clearly known to be changing rapidly, impacting our planet’s health, economy, geopolitics, and quality of life. The people and ecosystems of the Arctic have been among the first to suffer the results of greenhouse gas warming. They are also among the most affected. This is now causing significant climate instability throughout the Northern Hemisphere.
At the same time, climate change over the Antarctic and the Southern Ocean is altering the distribution of ecosystems and in particular water availability in Australia and South Africa, such as recent shortages in Cape Province. But this only represents the early stages of the polar regions’ response to human intervention in the climate system.
Dr. Paul Andrew Mayewski is Director of the Climate Change Institute at the University of Maine in the United States. He has led more than 55 expeditions to some of the remotest polar and high altitude reaches of the planet. Mayewski is also recipient of numerous honours such as the first internationally awarded Medal for Excellence in Antarctic Research and the Explorers Club Lowell Thomas Medal.
Acknowledgements: We thank Dr. Sean Birkel, Climate Change Institute, University of Maine, the developer of the Climate ReanalyzerTM software utilized in all of the graphics in this paper.
Other articles in the Special Series on Polar Regions.
Business in the Arctic: Infrastructure or investment? Which comes first?
Northern Reindeer: Adapting to survive
POLAR FOCUS: Including the Sixth Sense in Arctic Work
Polar Focus: The impact of climate change on the world’s Polar regions can no longer be ignored.
Polar Polarity: A Letter from Iceland
Polar2018: Bringing the Arctic and Antarctic together in Switzerland
Polar2018: Bringing the Arctic and Antarctic together in Switzerland