EDITORIAL 2: Artic sea-ice melting has slowed, but here’s why this isn’t good news
Context
For more than half a century, the melting of sea ice in the Arctic has been among the most well-known indicators of climate change. But a new study has revealed that the pace of sea ice loss has slowed down in the past 20 years.
Why has Arctic sea ice loss slowed down in the last 20 years?
- It has long been established that human activities — primarily, the burning of fossil fuels that emits heat-trapping greenhouse gases (GHG) — have led to a rise in global temperatures. In the Arctic, this warming has led to the melting of sea ice.
- Research has shown that the region has lost more than 10,000 cubic kilometres of sea ice since the 1980s
- Anthropogenic global warming, however, does not do away with natural variations in the Earth’s climate system (although it can affect these).
- One such variation is the El Niño-Southern Oscillation (ENSO), which refers to a fluctuation in sea surface temperatures (SSTs) in the equatorial Pacific Ocean that occurs every two to seven years.
- ENSO influences, alters, and interferes with global atmospheric circulation, which, in turn, influences the weather worldwide.
- England suggests that natural climate variations, such as the Pacific Decadal Oscillation and Atlantic Multidecadal Variability, could be contributing to the slowdown in Arctic sea ice melting.
Decadal Oscillation and Atlantic Multidecadal Variability
- The Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Variability (AMV) are two major climate phenomena that involve long-term fluctuations in ocean temperatures, but they occur in different ocean basins and on slightly different timescales.
- The PDO is a pattern of warming and cooling in the North Pacific Ocean, oscillating over periods of 5 to 20 years.
- The AMV is a mode of variability in the North Atlantic, characterized by sea surface temperature changes over roughly 60-year cycles.
- These two modes can influence global weather patterns, and recent research suggests they also interact and modulate each other through the atmosphere.
- These long-term fluctuations can bring unusually cool waters into the Arctic, reducing sea ice loss or even causing expansion in some regions.
- According to the study, the melt rate over the past 20 years has been around 0.35 square kilometres per decade, compared to the peak rate between 1993 and 2012, which was at least four times higher, closer to 1.3 million square kilometres per decade.
Does this mean that climate change is also slowing down?
- Humans continue to release unprecedented levels of GHG into the atmosphere, and mean global temperatures continue to rise.
- There is thus no indication that the slower Arctic sea ice melting implies that climate change is also slowing down.
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- Studies also revealed that the current slowdown is only temporary and there is a 50% chance that it lasts for five more years, and a 25% chance that it lasts another 10 years.
- The study highlights that once the slowdown stops, there is a risk of a more rapid decline in sea ice cover in the coming years.
Conclusion
The loss of sea ice in the Arctic would have far-reaching consequences. It will exacerbate global warming, lead to further rise of sea levels, and present unprecedented challenges to ecosystems that are dependent on sea ice.