[Interview file] Greenland melts'fastest ever'... It seems that the unprecedented speed will continue

In 2019, Greenland melted 532 billion tonnes of ice sheet (ice sheet continental glaciers) in one year.

In July alone, 230 billion tons were melted, which is equivalent to the annual average of the 2000s.

The amount that needs to be melted over a year has melted in just one month.

Over 530 billion tons of ice sheets that had melted during the year entered the sea, raising the Earth's total sea level by 1.5 mm.

Sea level usually rises by 3 to 4 mm a year due to climate change, but in 2019, Greenland alone raised 1.5 mm.

As such, ice sheet losses in Greenland have a very large impact on sea level rise.

Greenland's ice sheet loss has contributed the most to sea level rise in the last 10-20 years.

Unlike sea ice floating in water, ice that covers the land raises the sea level as it melts.

The melting of the ice in the ice cup does not change the height of the ice cup, but it is the same principle that the height rises when water is added from the outside.* The problem is that we do not fully understand the climate change occurring in Greenland.

The results of the IPCC report (5th)**, which are now available, also did not include information on glaciers on land.

In fact, it is said that there is a strong possibility that the temperature will rise faster and the sea level will rise higher than the climate change we are currently predicting.

* Of course, when sea ice in the Arctic Ocean melts, the water level rises.

Seawater is different from pure water without salt.

**IPCC (Intergovernmental Council on Climate Change) Report: The 6th is currently being prepared, and the 6th will contain content on continental glaciers.

We don't know much about Greenland, which melts at the fastest ever.

Ice on land, such as Greenland and Antarctica, causes sea level rise by the amount that melts immediately.

As such, it is an important factor in predicting the outcome of climate change, but the information on ice sheet loss was not included in the climate prediction model, which is a computer program.

There are several reasons why it is difficult to predict ice on land like Greenland.

First, the thick ice itself, which is more than 3 km long, makes observation difficult.

Data on the Greenland ice sheet are inadequate compared to the Arctic sea ice in the same northern high latitude region.

Due to the lack of data, there is bound to be a limit to predicting volatility.

Also, the enormous pressure on the ice sheet by its size makes predictions more difficult.

Predictive models, which are computer programs, predict climate based on various physical equations.

However, the ice sheet under great pressure is neither completely solid nor completely liquid.

It's like a toothpaste or paint-like state (non-newtonian fluid), and these materials are difficult to predict because they don't follow the laws of physics based on existing models.

Greenland, which melted 33 billion tons per year in the 1990s, melted 230 billion tons per year in the 2000s, and the speed has increased seven times.

The rate of melting is accelerating due to global warming, and the trend is unusual.

So, is the pace of 2019, when 530 billion tons melted, is one of these trends?

Or should it be viewed as an exceptional case for a specific year?

Will Greenland's future be okay?

Recently, an overseas research team studied Greenland's ice sheet loss from 12000 years ago to 2100 years into the future.

The team estimates that the recent ice sheet loss in Greenland is a major loss that has not been in the past 12,000 years.

The melting ice sheet in Greenland has gone beyond natural control.

The research team predicted that the same trend will continue in the future for ice sheet losses.

The study calculated ice sheet loss by putting existing IPCC climate data into a new model that predicts only land ice.

As a result, depending on the climate scenario, ice will disappear from 8 trillion tons (RCP 2.6*) to 35.9 trillion tons (RCP 8.5) within the 21st century.

Currently, Greenland's climate is changing closer to the RCP 8.5 scenario, so by the end of this century, nearly 36 trillion tonnes of ice are expected to melt in Greenland alone.

According to this prediction, Greenland alone raises the sea level by 10cm in the remaining 21st century.

*RCP (Climate Change Scenario Representative Concentration Pathways): 2.6 (Scenarios with a lot of GHG reduction), 8.5 (Scenarios where GHG reduction is rarely achieved)

Promoting Warming The Northern Hemisphere warms faster than the Southern Hemisphere.

In particular, the effect is greater at high latitudes where the Arctic and Greenland are located than at low and mid latitudes.

The regional characteristics of the Arctic Ocean and Greenland will also accelerate warming, but each is contributing to the rise in temperature by affecting each other.

As the glaciers melt, the Arctic Ocean region receives more solar heat, and the water formed by the melting of the ice is in contact with the surrounding ice due to sea level rise and melts the Arctic Ocean ice faster.

Last July, the arctic glacier area was the lowest ever, and in winter, it is also at a record low.

Arctic temperatures were about 5℃ higher than normal this winter.

The surrounding environment is also by no means a positive situation for Greenland's future.

The future will change according to our efforts, but the future of White Greenland is still dark.

<References>

JJason P. Briner et al., "Rate of mass loss from the Greenland Ice Sheet will exceed Holocene values ​​this century", nature(2020) 586, 70–74, doi.org/10.1038/s41586-020- 2742-6

Ingo Sasgen et al., "Return to rapid ice loss in Greenland and record loss in 2019 detected by the GRACE-FO satellites", nature communications Earth & Environment (2020) volume 1, doi.org/10.1038/s43247- 020-0010-1