Climate tipping points: The Arctic is a bellwether for irreversible change

The warship HMS Terror lies at the bottom of the Arctic Ocean in the Northwest passage, lost in 1848 after two grueling years stuck in the Arctic ice. Rescue missions launched to recover the ship in 1851 suffered the same fate, crushed under the year-round ice that encased Northern Canada and the Arctic Ocean. But in 2016 — just 168 years later — the Victoria Strait was clear of ice, allowing the recovery of the HMS Terror and beckoning exploration of the most northern reaches of the globe. 

The Arctic is iconic for maintaining year-round ice and snow, but in the last decade, it has begun to transition to wetlands and open ocean. Emblematic of this change, in July 2020, the last intact ice shelf in the Canadian Arctic fell into the sea. Since first analyzed in 1902, the Milne ice sheet already lost 43 percent of its previous mass. Canada's Ellesmere Island ice caps were also lost in the summer of 2020, as the ice deposited during the Little Ice Age (1600 to 1850) melted completely. Glacier melt, thawing permafrost and wetland expansion create a new landscape, changing ecosystems as well as altering the global atmosphere and ocean circulation.   

The term “tipping point” is often applied to a moment of critical change in human history. In ecology, tipping points describe small changes that, over time, force an irreversible change. Yearly lows of sea ice and a startling increase in permafrost thaw in a warming climate signal that the tipping point has already been crossed. We have already lost the frozen Arctic.

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At this critical moment of loss, we must use the Arctic tipping point as a hard lesson — as ecosystems worldwide approach tipping points.

Small tipping points expand through ecosystems

As ice and snow are lost, the warming climate makes it difficult to recover. Sea ice that is only a few months old covers gaps in the Arctic Ocean, with yearly loss of old ice greater than the annual gain. In 2019, the National Oceanic and Atmospheric Administration (NOAA) reported that just 1 percent of the Arctic Ocean ice older than four years old remained. A warming atmosphere and sea prevent ice growth, leading to an ice-free Arctic Ocean.

In the summer of 2020, Arctic wildfires expanded across the tundra — driving permafrost thaw and triggering meltwater infiltration. In the permafrost, water from small thaw areas expand laterally, warming the surrounding permafrost ice. Gradually, disconnected thaw expands across a large area, abruptly transforming frozen ecosystems to wetlands. In pockets of permafrost and ice melt, vegetation grows at unprecedented rates. Once permafrost thaws, ongoing atmospheric warming makes a return to stable permafrost impossible.

The rapidity of Arctic change has surprised researchers and the public alike. Until recently, climate change models failed to identify that the combination of fire, ice loss, and land clearing would force tipping point thresholds. In many cases, these small-scale, discrete events expand across the landscape to create enduring change.

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A bellwether for future change

After the hottest summer on record, its clear climate change has already transformed the Arctic — a bellwether for irreparable climate change. Our fragile Arctic must be the first and last system to cross a permanent tipping point.

Around the world, ecosystem tipping points loom as wildfire, human land use and biodiversity loss exponentially increase and magnify climate impacts. Expanding ocean dead zones, coral reef bleaching and rainforest loss are emblematic of system collapses — and are slowly combining to create global tipping points. There is very little time to alter the trajectory of Earth's ecosystems, halting climate-driven collapse. To protect the Earth's incredible diversity and stability, we must acknowledge that climate change is already permanently changing the planet — and we have little time to change course. 

Kimberley R. Miner, Ph.D., is a Climate Change Institute research assistant professor at the University of Maine. She works on the Arctic Methane Project looking at the impacts of climate change in the Arctic. Miner’s opinions are her own and do not reflect those of the University of Maine.