Norway. I stand on the edge of the Greenland ice sheet, mesmerized by a breathtaking view of natural destruction. A mile wide front of the glacier has broken off. Separating from a huge iceberg, it is falling into the sea. Huge pillars of ice, of the height of a three-storey building, are rolling here and there like dice. As soon as a huge piece of this glacier falls into the sea – many tons of snowflakes are seen flying in the air. The high waves that rise after this submerge everyone in their path.
Luckily, I’m watching it all from a cliff a few miles away. But even here, I can feel the seismic tremors. Despite the spectacle, I am well aware that this is bad news for the world’s low-lying beaches. As a field glaciologist, I have worked on ice sheets for more than 30 years. In that time I have seen some amazing changes. The past few years have been particularly significant because of the rapid rate and magnitude of the ongoing change. My books taught me that ice sheets react on millennium time scales, but that’s not what we’re seeing today.
A study published on 29 August 2022 shows that the Greenland ice sheet is now so out of balance due to the current Arctic climate that it can no longer maintain its current shape. It is irreversibly committed to being reduced by at least 59,000 square kilometers (22,780 sq mi), an area much larger than the Protected State of Denmark in Greenland.
Even if all greenhouse gas emissions driving global warming stop, we find that Greenland ice loss would raise global sea levels by at least 10.8 inches (27.4 cm) under current temperatures. This is higher than the current model forecast. If every year was like 2012, when Greenland experienced a heat wave, the irrevocable commitment to sea level rise would triple. This is an ominous sign, given that these are the climatic conditions that we have already observed, not a hypothetical future scenario.
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Our study takes an entirely new approach – it is based on observation and glacial theory rather than sophisticated numerical models. The current generation of coupled climate and ice sheet models used to predict future sea level rise have failed to capture the emerging processes we see driving Greenland’s ice loss.
How did Greenland reach this point?
The Greenland ice sheet is a huge, frozen reservoir that looks like an inverted bowl. The ice is in constant flux, flowing inward – where it is more than 1.9 miles (3 kilometers) thick, cold and icy. Overall, the ice sheet holds enough fresh water to raise global sea levels by 24 feet (7.4 meters).
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Greenland’s terrestrial ice has existed for about 26 million years and expanded and contracted with two dozen ‘ice age’ cycles, lasting 70,000 or 100,000 years, punctuated by a nearly 10,000-year warm interglacial. Each glacier is driven by a change in the Earth’s orbit which controls how much solar radiation reaches the Earth’s surface. These variations are then reinforced by snow reflectance, or albedo; atmospheric greenhouse gases; and the ocean circulation that redistributes that heat around the planet.
We are currently passing through an interglacial period – the Holocene. For the past 6,000 years Greenland, like the rest of the planet, has benefited from a mild and stable climate with an ice sheet in equilibrium – until recently. Since the 1990s, as the atmosphere and oceans have warmed under rapidly rising greenhouse gas emissions, Greenland’s mass balance has deteriorated. The loss of snow due to excessive melting of snow, rain, snow flow etc. is now much more than the accumulation of snow.
what does the future hold?
The questions are important, how fast is Greenland losing its ice, and what does this mean for future sea level rise? Greenland’s ice loss is contributing about 0.04 inches (1 millimeter) per year to global sea level rise over the past decade. This net loss is split between surface melting and dynamical processes that accelerate outward glacier flow and are greatly amplified by atmospheric and ocean warming, respectively. To explain it in simple words, it can be said that ice sheets do not like hot weather or water flow, and there is heat.
Models used by the Intergovernmental Panel on Climate Change forecast a sea level rise of about 4 inches (10 cm) over Greenland by 2100, with a worst-case scenario of 6 inches (15 cm). But this prediction differs from what scientists in the region are seeing from the ice sheet itself.
According to our findings, Greenland will lose at least 3.3% of its ice, more than 100 trillion metric tons. The damage has already been done – ice that must melt and break up icebergs, in order to re-establish Greenland’s balance with the current climate.
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it’s still not too late
The consequences of devastating coastal flooding in the form of sea level rise are still unimaginable for the billions or more people who live in the low-lying coastal regions of the planet. Personally, I hope we can get back on track. I don’t feel like we’ve overstepped the limits of improvement, it’s not too late to act on what I understand about the ice sheet and the insights that our new study brings. But fossil fuels and emissions must be reduced now, as time is short and water levels are rising – faster than forecast. (agency input)
FIRST PUBLISHED : August 30, 2022, 23:03 IST