Time will tell if this is a record summer for Greenland ice melt, but the pattern over the past 20 years is clear



Melting on top of sea ice off northwestern Greenland, June 2019.
Steffen M. Olsen/Twitter

Nerilie Abram, Australian National University

Greenland has been in the news a bit lately. From Huskies seemingly walking on water, to temperatures soaring to 20℃ above average for the time of year, to predictions of the vast ice sheet being lost entirely, what is going on?

At its most simple: ice melts when it gets too warm.

Of course, some ice melts every time summer rolls around, but the amount of Arctic ice that melts each summer is growing, and we’re waiting to see whether this turns out to be a record-breaking year for Greenland ice melt.

No part of the planet is free from the impacts of human-caused climate change. But Greenland, and the Arctic more generally, is experiencing the impacts particularly severely. Temperatures in the planet’s extreme north are rising twice as fast as the global average.

Amplification of climate change in the Arctic.




Read more:
Ice melt in Greenland and Antarctica predicted to bring more frequent extreme weather


Greenland is warming so rapidly because of what climate scientists refer to as a “positive feedback”. Despite the name, these are not good. A better term might be “climate change amplifier”.

The Arctic has many “positive feedbacks” or “amplifiers” that worsen the effects of climate change here. For example, as snow and ice begin to melt, the surface darkens, allowing it to absorb more heat and thus melt even more.

This effect is most dramatic when snow and ice are lost completely, as in the case of the dramatic loss of the sea ice covering the Arctic ocean. Arctic sea ice loss is one of the major factors that explains why the Arctic is warming so much faster than the rest of the planet.

Another worrisome characteristic of climate change in the Arctic is the potential for ice melt to accelerate. The temperature threshold at which ice begins to melt means that once the climate has warmed enough to start melting ice, any further warming will rapidly cause an even larger amount of melting to occur. That is the reality beginning to play out in Greenland.

Beginning of the 2019 summer melt season

Last month, ice melt across the surface of Greenland made headlines. Surface melting spiked rapidly and was unusually strong for June. Melting was most intense around the edges of the Greenland ice sheet, and about 40% of the entire ice sheet surface was affected to some extent.

Greenland ice melt is typically very irregular during each summer, spiking as weather systems bring warm air masses over the ice sheet. Given this variability, it is not yet clear whether 2019 is going to be an unusually bad year for melting over Greenland – and whether it will rival the worst year on record, 2012, when the entire surface of the ice sheet experienced melting.

But what is very clear from observations since the 1970s (and completely consistent with simple physics) is that as the Arctic climate warms, the Greenland summer melt season is starting earlier, lasting longer, and becoming more intense.

Samples of older ice from inside Greenland’s ice sheet paint an even clearer picture of the changes that climate warming is causing. The amount of summer melting first began to increase in the mid-1800s, not long after human-driven climate warming began. Summer melt over the past two decades has reached levels roughly 50% higher than before the Industrial Revolution, and the speed of ice loss from the Greenland sheet has increased nearly sixfold since the 1980s.

Greenland melt intensity over the past 350 years.




Read more:
The Industrial Revolution kick-started global warming much earlier than we realised


Choices for the future

An ice sheet has existed on Greenland for millions of years. But the geological timescales of ice sheet growth and renewal are vastly outpaced by the human-caused changes we see today.

A study published in June this year, at the same time surface melting of the ice sheet was spiking, predicts that if human greenhouse emissions continue unabated, by the end of this century ice loss from the Greenland ice sheet could see the ocean rise by up to 33cm.

If all of the Greenland ice sheet were to melt, global sea level would rise by more than 7 metres. According to the same study, that could potentially happen within 1,000 years.




Read more:
Cold and calculating: what the two different types of ice do to sea levels


The evidence is abundantly clear: the rising temperature of the planet is causing more Arctic ice to melt during the northern summer. We cannot avoid further ice loss in coming decades, and people and ecosystems will have to adapt to this.

But there is still a window of opportunity to avoid the worst impacts of future climate change in the longer term. The evidence tells us that the only way to prevent the destruction of the Greenland ice sheet, and multi-metre rises in global sea level, is to make rapid, deep cuts to greenhouse gas emissions. That is a choice we still have a chance to make.The Conversation

Nerilie Abram, ARC Future Fellow, Research School of Earth Sciences; Chief Investigator for the ARC Centre of Excellence for Climate Extremes, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Ice melt in Greenland and Antarctica predicted to bring more frequent extreme weather



File 20190204 193206 1wihd6q.jpg?ixlib=rb 1.1
A new climate model combines data on ice loss from both polar regions for the first time.
Mark Brandon, CC BY-ND

Nick Golledge, Victoria University of Wellington

Last week, rivers froze over in Chicago when it got colder than at the North Pole. At the same time, temperatures hit 47℃ in Adelaide during the peak of a heatwave.

Such extreme and unpredictable weather is likely to get worse as ice sheets at both poles continue to melt.

Our research, published today, shows that the combined melting of the Greenland and Antarctic ice sheets is likely to affect the entire global climate system, triggering more variable weather and further melting. Our model predictions suggest that we will see more of the recent extreme weather, both hot and cold, with disruptive effects for agriculture, infrastructure, and human life itself.

We argue that global policy needs urgent review to prevent dangerous consequences.




Read more:
We finally have the rulebook for the Paris Agreement, but global climate action is still inadequate


Accelerated loss of ice

Even though the goal of the Paris Agreement is to keep warming below 2℃ (compared to pre-industrial levels), current government pledges commit us to surface warming of 3-4℃ by 2100. This would cause more melting in the polar regions.

Already, the loss of ice from ice sheets in Antarctica and Greenland, as well as mountain glaciers, is accelerating as a consequence of continued warming of the air and the ocean. With the predicted level of warming, a significant amount of meltwater from polar ice would enter the earth’s oceans.

The West Antarctic Ice Sheet is considered more vulnerable to melting, but East Antarctica , once thought to be inert, is now showing increasing signs of change.
Nick Golledge, CC BY-ND

We have used satellite measurements of recent changes in ice mass and have combined data from both polar regions for the first time. We found that, within a few decades, increased Antarctic melting would form a lens of freshwater on the ocean surface, allowing rising warmer water to spread out and potentially trigger further melting from below.

In the North Atlantic, the influx of meltwater would lead to a significant weakening of deep ocean circulation and affect coastal currents such as the Gulf Stream, which carries warm water from the tropics into the North Atlantic. This would lead to warmer air temperatures in Central America, Eastern Canada and the high Arctic, but colder conditions over northwestern Europe on the other side of the Atlantic.

Recent research suggests that tipping points in parts of the West Antarctic Ice Sheet may have already been passed. This is because most of the ice sheet that covers West Antarctica rests on bedrock far below sea level – in some areas up to 2 kilometres below.




Read more:
How Antarctic ice melt can be a tipping point for the whole planet’s climate


Bringing both poles into one model

It can be a challenge to simulate the whole climate system because computer models of climate are usually global, but models of ice sheets are typically restricted to just Antarctica or just Greenland. For this reason, the most recent Intergovernmental Panel of Climate Change (IPCC) assessment used climate models that excluded ice sheet interactions.

Global government policy has been guided by this assessment since 2013, but our new results show that the inclusion of ice sheet meltwater can significantly affect climate projections. This means we need to update the guidance we provide to policy makers. And because Greenland and Antarctica affect different aspects of the climate system, we need new modelling approaches that look at both ice sheets together.

When the edges of the West Antarctic Ice Sheet start to recede, they retreat into deeper and deeper water and the ice begins to float more easily.
Mark Brandon, CC BY-ND

Seas rise as ice melts on land

Apart from the impact of meltwater on ocean circulation, we have also calculated how ongoing melting of both polar ice caps will contribute to sea level. Melting ice sheets are already raising sea level, and the process has been accelerating in recent years.

Our research is in agreement with another study published today, in terms of the amount that Antarctica might contribute to sea level over the present century. This is good news for two reasons.

First, our predictions are lower than one US modelling group predicted in 2016. Instead of nearly a metre of sea level rise from Antarctica by 2100, we predict only 14-15cm.

Second, the agreement between the two studies and also with previous projections from the IPCC and other modelling groups suggests there is a growing consensus, which provides greater certainty for planners. But the regional pattern of sea level rise is uneven, and islands in the southwest Pacific will most likely experience nearly 1.5 times the amount of sea level rise that will affect New Zealand.

While some countries, including New Zealand, are making progress on developing laws and policies for a transition towards a low-carbon future, globally policy is lagging far behind the science.

The predictions we make in our studies underline the increasingly urgent need to reduce greenhouse gas emissions. It might be hard to see how our own individual actions can save polar ice caps from significant melting. But by making individual choices that are environmentally sustainable, we can persuade politicians and companies of the desire for urgent action to protect the world for future generations.The Conversation

Nick Golledge, Associate Professor of Glaciology, Victoria University of Wellington

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Greenland: how rapid climate change on world’s largest island will affect us all



File 20170818 7937 vmrbcz.jpg?ixlib=rb 1.1

Dan Bach Kristensen / shutterstock

Kathryn Adamson, Manchester Metropolitan University

The largest wildfire ever recorded in Greenland was recently spotted close to the west coast town of Sisimiut, not far from Disko Island where I research retreating glaciers. The fire has captured public and scientific interest not just because its size and location came as a surprise, but also because it is yet another signpost of deep environmental change in the Arctic.

Greenland is an important cog in the global climate system. The ice sheet which covers 80% of the island reflects so much of the sun’s energy back into space that it moderates temperatures through what is known as the “albedo effect”. And since it occupies a strategic position in the North Atlantic, its meltwater tempers ocean circulation patterns.

Most of Greenland is covered by more than a kilometre of ice.
Eric Gaba / NGDC, CC BY-SA

But Greenland is especially vulnerable to climate change, as Arctic air temperatures are currently rising at twice the global average rate. Environmental conditions are frequently setting new records: “the warmest”, “the wettest”, “the driest”.

Despite its size, the fire itself represents only a snapshot of Greenland’s fire history. It alone cannot tell us about wider Arctic climate change.

But when we superimpose these extraordinary events onto longer-term environmental records, we can see important trends emerging.

The ice sheet is melting

Between 2002 and 2016 the ice sheet lost mass at a rate of around 269 gigatonnes per year. One gigatonne is one billion tonnes. One tonne is about the weight of a walrus.

Leave my weight out of this.
BMJ / shutterstock

During the same period, the ice sheet also showed some unusual short-term behaviour. The 2012 melt season was especially intense – 97% of the ice sheet experienced surface melt at some point during the year. Snow even melted at its summit, the highest point in the centre of the island where the ice is piled up more than 3km above sea level.

Change in total mass of the Greenland Ice Sheet (in Gt) from 2002 to 2016. Red crosses indicate the values every April.
NOAA

In April 2016 Greenland saw abnormally high temperatures and its earliest ever “melt event” (a day in which more than 10% of the ice sheet has at least 1mm of surface melt). Early melting doesn’t usher in a period of complete and catastrophic change – the ice won’t vanish overnight. But it does illustrate how profoundly and rapidly the ice sheet can respond to rising temperatures.

Permafrost is thawing

Despite its icy image, the margins of Greenland are actually quite boggy, complete with swarms of mosquitoes. This is the “active layer”, made up of peaty soil and sediment up to two metres thick, which temporarily thaws during the summer. The underlying permafrost, which can reach depths of 100m, remains permanently frozen.

Fighting off the mosquitos in boggy Greenland.
Kathryn Adamson, Author provided

In Greenland, like much of the Arctic, rising temperatures are thawing the permafrost. This means the active layer is growing by up to 1.5cm per year. This trend is expected to continue, seeing as under current IPCC predictions, Arctic air temperatures will rise by between 2.0°C and 7.5°C this century.

Arctic permafrost contains more than 1,500 billion tonnes of dead plants and animals (around 1,500 billion walrus equivalent) which we call “organic matter”. Right now, this stuff has been frozen for thousands of years. But when the permafrost thaws this organic matter will decay, releasing carbon and methane (another greenhouse gas) into the atmosphere.

If thawing continues, it’s estimated that by 2100 permafrost will emit 850-1,400 billion tonnes of CO₂ equivalent (for comparison: total global emissions in 2012 was 54 billion tonnes of CO₂ equivalent). All that extra methane and carbon of course has the potential to enhance global warming even further.

With this in mind, it is clear to see why the recent wildfire, which was burning in dried-out peat in the active layer, was especially interesting to researchers. If Greenland’s permafrost becomes increasingly degraded and dry, there is the potential for even bigger wildfires which would release vast stores of greenhouse gases into the atmosphere.

Species are adapting to a changing ecosystem

Major changes in the physical environment are already affecting the species that call Greenland home. Just look at polar bears, the face of Arctic climate change. Unlike other bears, polar bears spend most of their time at sea, which explains their Latin name Ursus maritimus. In particular they rely on sea ice as it gives them a deep-water platform from which to hunt seals.

However, since 1979 the extent of sea ice has decreased by around 7.4% per decade due to climate warming, and bears have had to adjust their habitat use. With continued temperature rise and sea ice disappearance, it’s predicted that populations will decline by up to 30% in the next few decades, taking the total number of polar bears to under 9,000.

Where are you, seals?
Mario_Hoppmann / shutterstock

I have considered only a handful of the major environmental shifts in Greenland over the past few decades, but the effects of increasing temperatures are being felt in all parts of the earth system. Sometimes these are manifest as extreme events, at others as slow and insidious changes.

The different parts of the environmental jigsaw interact, so that changes in one part (sea ice decline, say) influence another (polar bear populations). We need to keep a close eye on the system as a whole if we are to make reliable interpretations – and meaningful plans for the future.The Conversation

Kathryn Adamson, Senior Lecturer in Physical Geography, Manchester Metropolitan University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Greenland: how rapid climate change on world’s largest island will affect us all



File 20170818 7937 vmrbcz.jpg?ixlib=rb 1.1

Dan Bach Kristensen / shutterstock

Kathryn Adamson, Manchester Metropolitan University

The largest wildfire ever recorded in Greenland was recently spotted close to the west coast town of Sisimiut, not far from Disko Island where I research retreating glaciers. The fire has captured public and scientific interest not just because its size and location came as a surprise, but also because it is yet another signpost of deep environmental change in the Arctic.

//platform.twitter.com/widgets.js

Greenland is an important cog in the global climate system. The ice sheet which covers 80% of the island reflects so much of the sun’s energy back into space that it moderates temperatures through what is known as the “albedo effect”. And since it occupies a strategic position in the North Atlantic, its meltwater tempers ocean circulation patterns.

Most of Greenland is covered by more than a kilometre of ice.
Eric Gaba / NGDC, CC BY-SA

But Greenland is especially vulnerable to climate change, as Arctic air temperatures are currently rising at twice the global average rate. Environmental conditions are frequently setting new records: “the warmest”, “the wettest”, “the driest”.

Despite its size, the fire itself represents only a snapshot of Greenland’s fire history. It alone cannot tell us about wider Arctic climate change.

But when we superimpose these extraordinary events onto longer-term environmental records, we can see important trends emerging.

The ice sheet is melting

Between 2002 and 2016 the ice sheet lost mass at a rate of around 269 gigatonnes per year. One gigatonne is one billion tonnes. One tonne is about the weight of a walrus.

Leave my weight out of this.
BMJ / shutterstock

During the same period, the ice sheet also showed some unusual short-term behaviour. The 2012 melt season was especially intense – 97% of the ice sheet experienced surface melt at some point during the year. Snow even melted at its summit, the highest point in the centre of the island where the ice is piled up more than 3km above sea level.

Change in total mass of the Greenland Ice Sheet (in Gt) from 2002 to 2016. Red crosses indicate the values every April.
NOAA

In April 2016 Greenland saw abnormally high temperatures and its earliest ever “melt event” (a day in which more than 10% of the ice sheet has at least 1mm of surface melt). Early melting doesn’t usher in a period of complete and catastrophic change – the ice won’t vanish overnight. But it does illustrate how profoundly and rapidly the ice sheet can respond to rising temperatures.

Permafrost is thawing

Despite its icy image, the margins of Greenland are actually quite boggy, complete with swarms of mosquitoes. This is the “active layer”, made up of peaty soil and sediment up to two metres thick, which temporarily thaws during the summer. The underlying permafrost, which can reach depths of 100m, remains permanently frozen.

Fighting off the mosquitos in boggy Greenland.
Kathryn Adamson, Author provided

In Greenland, like much of the Arctic, rising temperatures are thawing the permafrost. This means the active layer is growing by up to 1.5cm per year. This trend is expected to continue, seeing as under current IPCC predictions, Arctic air temperatures will rise by between 2.0°C and 7.5°C this century.

Arctic permafrost contains more than 1,500 billion tonnes of dead plants and animals (around 1,500 billion walrus equivalent) which we call “organic matter”. Right now, this stuff has been frozen for thousands of years. But when the permafrost thaws this organic matter will decay, releasing carbon and methane (another greenhouse gas) into the atmosphere.

If thawing continues, it’s estimated that by 2100 permafrost will emit 850-1,400 billion tonnes of CO₂ equivalent (for comparison: total global emissions in 2012 was 54 billion tonnes of CO₂ equivalent). All that extra methane and carbon of course has the potential to enhance global warming even further.

With this in mind, it is clear to see why the recent wildfire, which was burning in dried-out peat in the active layer, was especially interesting to researchers. If Greenland’s permafrost becomes increasingly degraded and dry, there is the potential for even bigger wildfires which would release vast stores of greenhouse gases into the atmosphere.

Species are adapting to a changing ecosystem

Major changes in the physical environment are already affecting the species that call Greenland home. Just look at polar bears, the face of Arctic climate change. Unlike other bears, polar bears spend most of their time at sea, which explains their Latin name Ursus maritimus. In particular they rely on sea ice as it gives them a deep-water platform from which to hunt seals.

However, since 1979 the extent of sea ice has decreased by around 7.4% per decade due to climate warming, and bears have had to adjust their habitat use. With continued temperature rise and sea ice disappearance, it’s predicted that populations will decline by up to 30% in the next few decades, taking the total number of polar bears to under 9,000.

Where are you, seals?
Mario_Hoppmann / shutterstock

I have considered only a handful of the major environmental shifts in Greenland over the past few decades, but the effects of increasing temperatures are being felt in all parts of the earth system. Sometimes these are manifest as extreme events, at others as slow and insidious changes.

The ConversationThe different parts of the environmental jigsaw interact, so that changes in one part (sea ice decline, say) influence another (polar bear populations). We need to keep a close eye on the system as a whole if we are to make reliable interpretations – and meaningful plans for the future.

Kathryn Adamson, Senior Lecturer in Physical Geography, Manchester Metropolitan University

This article was originally published on The Conversation. Read the original article.

Greenland: how rapid climate change on world’s largest island will affect us all



File 20170818 7937 vmrbcz

Dan Bach Kristensen / shutterstock

Kathryn Adamson, Manchester Metropolitan University

The largest wildfire ever recorded in Greenland was recently spotted close to the west coast town of Sisimiut, not far from Disko Island where I research retreating glaciers. The fire has captured public and scientific interest not just because its size and location came as a surprise, but also because it is yet another signpost of deep environmental change in the Arctic.

//platform.twitter.com/widgets.js

Greenland is an important cog in the global climate system. The ice sheet which covers 80% of the island reflects so much of the sun’s energy back into space that it moderates temperatures through what is known as the “albedo effect”. And since it occupies a strategic position in the North Atlantic, its meltwater tempers ocean circulation patterns.

Most of Greenland is covered by more than a kilometre of ice.
Eric Gaba / NGDC, CC BY-SA

But Greenland is especially vulnerable to climate change, as Arctic air temperatures are currently rising at twice the global average rate. Environmental conditions are frequently setting new records: “the warmest”, “the wettest”, “the driest”.

Despite its size, the fire itself represents only a snapshot of Greenland’s fire history. It alone cannot tell us about wider Arctic climate change.

But when we superimpose these extraordinary events onto longer-term environmental records, we can see important trends emerging.

The ice sheet is melting

Between 2002 and 2016 the ice sheet lost mass at a rate of around 269 gigatonnes per year. One gigatonne is one billion tonnes. One tonne is about the weight of a walrus.

Leave my weight out of this.
BMJ / shutterstock

During the same period, the ice sheet also showed some unusual short-term behaviour. The 2012 melt season was especially intense – 97% of the ice sheet experienced surface melt at some point during the year. Snow even melted at its summit, the highest point in the centre of the island where the ice is piled up more than 3km above sea level.

Change in total mass of the Greenland Ice Sheet (in Gt) from 2002 to 2016. Red crosses indicate the values every April.
NOAA

In April 2016 Greenland saw abnormally high temperatures and its earliest ever “melt event” (a day in which more than 10% of the ice sheet has at least 1mm of surface melt). Early melting doesn’t usher in a period of complete and catastrophic change – the ice won’t vanish overnight. But it does illustrate how profoundly and rapidly the ice sheet can respond to rising temperatures.

Permafrost is thawing

Despite its icy image, the margins of Greenland are actually quite boggy, complete with swarms of mosquitoes. This is the “active layer”, made up of peaty soil and sediment up to two metres thick, which temporarily thaws during the summer. The underlying permafrost, which can reach depths of 100m, remains permanently frozen.

Fighting off the mosquitos in boggy Greenland.
Kathryn Adamson, Author provided

In Greenland, like much of the Arctic, rising temperatures are thawing the permafrost. This means the active layer is growing by up to 1.5cm per year. This trend is expected to continue, seeing as under current IPCC predictions, Arctic air temperatures will rise by between 2.0°C and 7.5°C this century.

Arctic permafrost contains more than 1,500 billion tonnes of dead plants and animals (around 1,500 billion walrus equivalent) which we call “organic matter”. Right now, this stuff has been frozen for thousands of years. But when the permafrost thaws this organic matter will decay, releasing carbon and methane (another greenhouse gas) into the atmosphere.

If thawing continues, it’s estimated that by 2100 permafrost will emit 850-1,400 billion tonnes of CO₂ equivalent (for comparison: total global emissions in 2012 was 54 billion tonnes of CO₂ equivalent). All that extra methane and carbon of course has the potential to enhance global warming even further.

With this in mind, it is clear to see why the recent wildfire, which was burning in dried-out peat in the active layer, was especially interesting to researchers. If Greenland’s permafrost becomes increasingly degraded and dry, there is the potential for even bigger wildfires which would release vast stores of greenhouse gases into the atmosphere.

Species are adapting to a changing ecosystem

Major changes in the physical environment are already affecting the species that call Greenland home. Just look at polar bears, the face of Arctic climate change. Unlike other bears, polar bears spend most of their time at sea, which explains their Latin name Ursus maritimus. In particular they rely on sea ice as it gives them a deep-water platform from which to hunt seals.

However, since 1979 the extent of sea ice has decreased by around 7.4% per decade due to climate warming, and bears have had to adjust their habitat use. With continued temperature rise and sea ice disappearance, it’s predicted that populations will decline by up to 30% in the next few decades, taking the total number of polar bears to under 9,000.

Where are you, seals?
Mario_Hoppmann / shutterstock

I have considered only a handful of the major environmental shifts in Greenland over the past few decades, but the effects of increasing temperatures are being felt in all parts of the earth system. Sometimes these are manifest as extreme events, at others as slow and insidious changes.

The ConversationThe different parts of the environmental jigsaw interact, so that changes in one part (sea ice decline, say) influence another (polar bear populations). We need to keep a close eye on the system as a whole if we are to make reliable interpretations – and meaningful plans for the future.

Kathryn Adamson, Senior Lecturer in Physical Geography, Manchester Metropolitan University

This article was originally published on The Conversation. Read the original article.