Ice Sheets and the Climate
How Permanent Is the “Permanent Ice”?

Aerial view of the ice sheet, Greenland, North America
Whether ice sheets as here in Greenland, melt completely, or only to a considerable extent, makes little difference to humans, says Dr Maria Hörhold. | Photo (detail): Gabriel Gersch © picture alliance / imageBROKER

Greenland is seeing rain, not snow, and the Alpine glaciers are diminishing all the time. How likely is it that there will no longer be any ice sheets at the Poles in the foreseeable future, and what would that mean for us? An interview with Dr Maria Hörhold, a glaciologist at the Alfred Wegener Institute.

Dr Hörhold, Greenland recently saw rain rather than snow at an altitude of 3,200 metres. Is that something we should be worried about?

Firstly, it is important to point out that this is an extremely rare phenomenon. 2012 was the first time that melting across the entire Greenland ice sheet was observed. That was probably also connected to rainfall. To put this into its proper historical context: ice cores contain visible layers of melt in the form of bubble-free ice layers, but we cannot say for certain whether this is frozen rain or perhaps comes from refrozen surface melting. What we can say, however, is that the last time such an event occurred at such an altitude and across such a wide area must have been over 100 years ago, and that it also happened very rarely prior to that. It is therefore alarming that we are now seeing this several times within a short period of time. We are observing that the melting parts of the ice sheet are growing and that the amount by which the melting contributes to the mass balance is on the increase.
Many people claim that there will soon be no glaciers left. How likely do you think this scenario is?

We need to define clearly what we mean by glaciers. As far as Alpine glaciers in the mountains are concerned, we are seeing a massive decline everywhere. I believe it is very likely that we will experience huge losses in this context. Then there are the ice sheets in the Greenland and the Antarctic, the permanent ice. We are also observing a decline in mass there, though it is not clear whether it will vanish completely. It makes no difference to us as humans whether the Greenland ice sheet disappears completely or not, as even percentual amounts will cause sea levels to rise, which will affect millions of people.

What would this mean for us and the planet?

The Greenland ice sheet is made up of snow deposition and mass loss. This loss of mass is brought about by surface melting and by ice calving off into the sea in the form of icebergs. The sum of snow deposition minus mass lost equates to the mass balance of the ice sheet, which shows a certain equilibrium. However, we are seeing that this is becoming unbalanced as the ice sheet loses more mass than it gains. This is due above all to the rising temperatures. Our measurements reveal that the Greenland ice sheet is playing a growing role in the rise in sea levels. I am no expert as far as the consequences for humankind are concerned. But it is not difficult to guess what rising sea levels will mean for those millions or billions of people who live in coastal regions and are directly affected. We will also be affected here in Bremerhaven, which is home to the Alfred Wegener Institute where I work. Precautionary measures need to be taken, and the most important thing is to limit the increase in temperature.

What role in terms of the climate is played by the warming of the Arctic?

The polar regions are covered with snow and ice that reflect the sunlight which falls on them. There is a considerable temperature difference between the polar regions and the lower latitudes, i.e. between the Arctic and Europe. This contrast influences our atmospheric circulation – and therefore the weather in Europe, too. As the Arctic is warming up, the temperature difference as compared with Europe is becoming smaller. The blocking events that are now being reported in the media refer to the phenomenon that this reduced temperature contrast means that weather systems are moving much more slowly, and are therefore remaining in one place for longer. And this can then lead to events such as constant rain or persistent drought.

To what extent is the melting related to the heat that is emitted from the core of the Earth, and what does this have to do with climate change?

It is important to understand that these are quite separate processes: obviously we have geothermal heat, which is radiated heat that comes out of the Earth and changes over the course of geological timeframes, i.e. over thousands of years. This is also the case beneath the Greenland ice sheet. This now features in the media because it has been measured directly for the first time. Direct measurements form a better basis for modelling. Geothermal heat is an important factor: the ice lies on the surface of the Earth, and the weight of the ice and the geothermal heat result in slight melting on the underside of the ice sheet, which influences how the ice flows. That said, the surface melting that we are observing at the moment is happening much faster, and that is being driven solely by the change in temperature. This is taking place on a quite different timeline than with geothermal heat. The loss in ice sheet mass is being accelerated by oceanic and atmospheric feedbacks.

In light of all this, should we not rather be concentrating on countering any potential consequences, or can this melting process still be halted?

There are two aspects. On the one hand, yes, we have an increased concentration of CO2 – twice as much as in pre-industrial times – and we will definitely feel the consequences of this, so the process of climate change is now beginning. There is no way we can avoid this. And yes, we therefore need to face up to the consequences of rising sea levels. At the same time, we have to ask ourselves how far we are willing to let climate change proceed, and what we will do to curtail it. Almost all countries have agreed on the 1.5 degree target and said that the consequences of any global warming beyond that are so serious that we cannot allow it to happen. Yet we also need to take very active steps right now if this target is to be reached. And we are still a long way from doing so. Climate change is happening and we must prepare for it, but we also have to work on how to limit it – these are parallel paths we need to follow.

How can we limit global warming?

The predicted increase in temperature is linked to the level of carbon emissions. We need not only to reduce emissions but to bring them down to zero, and indeed to actively remove carbon dioxide from the atmosphere. All the scenarios described in the climate reports highlight ways of achieving this. They show that if we want to keep the 1.5 degree limit, we are talking about seven or eight years in which we would still be allowed to emit CO2 at current levels. That is not much time to restructure an entire economy or adapt our lifestyles. If we want to succeed, we must change something now, and do so very radically.

But how will changing our habits here in Germany now help the ice sheet in Greenland?

It is vital for us to understand that we in Germany are among the biggest emitters of carbon dioxide worldwide. Though we account for a minimal proportion of the global population, we have extremely high per-capita carbon emissions, and they must be reduced. This is also a question of climate justice. These days, it is not right to say that we will only take care of what happens in Germany, and that the rest of the world is none of our business.

As a researcher, are you more optimistic or pessimistic that we can still reduce the scale of the problem, and that the catastrophic consequences can still be limited?

That is a very complex question: I’m not a sociologist, nor a psychologist. We all know what the problem is. What I believe we should be working towards in all studies and communicating externally is that we can change something. It is in our hands. We have the ideas and the approaches and the technologies. That makes me optimistic. Another thing that makes me optimistic is that I believe our swarm intelligence will come into play once we as a society finally take the problem seriously and tackle it. In my opinion we have a great deal of potential, but obviously we will make no progress for as long as the problem continues to be played down and trivialized. How little political will there is to bring about genuine change makes me somewhat pessimistic, however. I often talk to people in the street, and once a month we take part in a climate vigil together with Fridays for Future. I do my best to make it clear to everyone that we have many possibilities – but we must get started.

The questions were asked by Natascha Holstein, online editor of the Zeitgeister magazine.