The Greenland story

It was all over the news, all over the world: 97% of the surface of the Greenland Ice Sheet melting! Quite a lot of sources, including 350.org,  de Volkskrant and het NOS journal got carried away, and announced, either on twitter or on national TV, that 97% of all Greenland ice was gone. They should have spent a second to ponder this: for instance, the offices of de Volkskrant would be flooded if that had indeed been the case. But 97% of the surface experiencing melt is spectacular enough in itself. Generally, no more than 50% undergoes melting in summer. 97% is really rare.

Some twitter sources also mentioned this event had been predicted. In an article, that attracted quite some attention, Jason Box of Ohio State University, and co-workers, stated they expected melt over 100% of the surface to occur in the near future. So what did they base that on, and were they really that precise?

The map showing decreased reflectivity over almost the whole of the ice cap, which gets the bulk of the attention.

Box et al. studied the reflectivity of the Greenland ice. Reflectivity, or albedo, is one of these things that stabilises ice sheets; it reflects sunlight back so effectively that the radiation can hardly make a start at melting any ice before it finds itself reflected back into space. But if high temperatures manage to get the melting process going, this lowers the reflectivity, and then your ice and snow are in peril. This self-reinforcing process, also known as positive feedback, might well herald your ice cap’s decline. What’s even worse is dirt blown on top of the snow; this may start melt at lower temperatures.

So what did Box and his fellow scholars do? They basically measured reflectivity and melt from a satellite, calibrated these results with observations from weather stations on the surface, and ran a climate model in order to get an idea of the sensitivity of the reflectivity to temperature. And what is so new about this research? Satellites have been measuring the albedo of Greenland for many years, and ground-truthing with weather stations has been done since early days too. But the results of Box et al. go all the way to the year 2011, bringing this research up to date. And their combination of observations and modelling could potentially give new insights in how the process works.

Observations of reflectivity

So what did Box and colleagues find? The reflectivity of the Greenland Ice Sheet is at a low point; 8% lower in 2011 than it was in 2000. And this is not an incident; they have observed a significant trend, though admittedly a short-term one. They further found a 26% increase in melt between 2000 and 2011. And to give you an idea of how much that is: if that rate would remain constant at 2011 level, the ice cap would be lost in roughly 6000 years. And the sensitivity of the reflectivity to temperature? That’s where it gets confusing. Over large areas of the ice sheet, reflectivity only goes up with higher temperatures. This can be explained by warm air bringing in more snowfall. But strangely enough, snowfall doesn’t always correlate with higher reflectivity in their data. And when you look at the sensitivity of the reflectivity to temperature, or in other words; by how much the albedo goes up or down with every degree temperature change, it becomes clear that their data is only statistically robust in the regions that are melting already.

The authors warn that they think summer melting will occur over the entire ice sheet in another decade, if the coming years will be like 2010 and 2011. But that is a big “if”. Box emphasizes only the decreased reflectivity in his own blog post, without being too specific about the lack of straightforward relation with actual melting. The big take home message of this paper might be that the processes governing ice melt are not yet sufficiently understood. And we want to understand it, if only to get an idea what we should do with our coastal defences. The amount of melt in 2011 measured already translates to more than a millimetre of globally averaged sea level rise. And that does not sound like much in itself, but it does when you realise it was only 1.7 mm/year on average for the 20^th Century in total; that includes for instance Antarctica, mountain glaciers, and thermal expansion.

So did they predict the ~100% melt?

Well. In a way they did. But what they really predicted was a shift to net melt over the area that nowadays experiences net snow accumulation, averaged over the whole summer. They did not mention short periods of 100% surface melt. However, you can’t get to net summer melt without, well, melting large areas of the surface once in a while. So people who say “they predicted this!” are exaggerating. But Box and colleagues are right in saying that this event greatly supports their conclusions. Given the uncertainties in their data, this was more a lucky guess than rock-hard data, yet I hope it will attract attention to the danger of Greenland melt. It’s not as if we who are alive today will ever see an ice-free Greenland, but we may well see a Greenland Ice Cap that raises average sea level by 2mm per year or more, and that is something we need to prepare for. Those who love Amsterdam, London, New York or one of these other iconic cities near sea level might wish Box luck in keeping up the good work…

What is a species? And why care?

What is a species? A nice rule of thumb is that a group of organisms that can produce fertile offspring together is a species. And as long as you are dealing with nicely large, long-living, accessible species like cats and horses that will do. But what if you are dealing with organisms whose reproduction has never been observed? And why would it matter?

It helps to define species, even if you can’t be too sure of whether you’re actually getting it right. If I say I saw a picture of a dragon, you will all have an idea of what I saw, even though nobody could possibly conclusively define a dragon. If people know what you mean a lot is won. The same holds in micropalaeontology.

Micropalaeontology is the study of microfossils; the preserved remains of micro-organisms. An example of a group of such microorganisms is foraminifera; unicellular organisms that live in the sea, and produce little shells. That shell is what can remain preserved when the organism dies: the microfossil. They tend to be 0.1 to 1 mm in size. Their use in environmental science is endless; they are widespread and abundant, and there are many different species with each their own environmental preferences. Their evolution is fairly well-studied as well; if you show a micropalaeontologist a handful of foraminifera, he or she can most likely tell you, after barely more than a glance, how old they are, and what environment they lived in. And even their little shells can be studied; they can hold a wealth of information.

An example of an assemblage of foraminifera; in this case form Myanmar/Burma. Picture: Psammophile. Source: Creative Commons.

But back to the question of subdividing them into species. Traditionally, species have been defined on the basis of shape. Later, when more information became available, environmental preferences were taken into account as well. The whole classification of species was episodically revised, based on new information; the result was an ever-changing system, where not everybody used the same version. But everybody knew that; as long as you knew what classification someone used you knew, more or less, what you were up to. But a certain level of subjectivity cannot be avoided. Not every specimen looks like a textbook figure. But in spite of its confusions and imperfections, the system worked.

And then DNA analysis was invented. Suddenly, it could be objectively determined if organisms belong to the same species or not. And it is done on foraminifera too. When there was a workshop on foraminifera taxonomy (species classification), the researchers working on foraminifera DNA decided to put the old system to the test. They provided the participants of the workshop with 40 pictures of foraminifera of a specific genus of which they had sampled the DNA: they therefore knew which of these belonged to the same species. And now they asked us to group them the old way, and tell us what name they would give these species.

These are specimens of Ammonia beccarii; a species that has sometimes been subdivided into various species, but of which DNA research has revealed that it is indeed only one. Photo: Hans Hillewaert. Source: Creative Commons.

The first thing that became apparent was that it wasn’t an easy job. Every group of experts struggled! And every group came up with slightly different results. And the names assigned to the species did not always match either. That is a measure of the mentioned flexibility in classification, and subjectivity. But then they were shown what the DNA had revealed.

Some results were as expected. Sometimes the old-fashioned method split a species into two different ones, or left a specimen out that looked odd, but that is all within expectation. But there were shocks too: some species turned out to contain specimens that look quite different, and that none of the participants would have considered to be the same species, if they would find them in their samples. That provided food for thought.

Foraminifera pictures taken with a Scanning Electron Microscope; the top left is classified as an Ammonia beccarii, like the specimens in the picture above. And according to the USGS, the top right is an Elphidium excavatum forma clavatum, but are they sure? This was one of the species that created some confusion in the "shape vs DNA" game... 

Does this mean we have to forget about micropalaeontology? No; as flawed as the discipline is, it still answers (and raises!) very relevant questions. And it helps to know how big the uncertainties are. Does this mean we have to now sample the DNA of all foraminifera we study? No; that would be too time- and money-consuming, and beside that; most of the specimens we study are long dead, and don’t contain DNA anymore. So what is the relevance of this work?

To give you an idea of how confusing it is: one of these pairs are two specimens of the same species, but the other pair is two different species. I'm not going to say which is which, but I think it illustrates similarity isn't enough to decide. 

One of the things DNA research can do is tell the micropalaontological community which differences in shape are indicative of a different species, and which are just variation within a species. They could improve on their classifications that way. The research can also help in cases where a species seems to be able to adapt to very different environments; can they really, or are we dealing with several species that look the same? Knowing that would tell us something about the adaptability of marine species; quite useful knowledge in these times of rapid change. Various experts probably already have a long list of further questions they would like to see answered, and the process of answering will create a multitude of new questions. It’s even possible we’ll see new species evolve into existence right under our eyes…

North Carolina and the sea - an update

Is North Carolina asking citizens to think for themselves? Regulations, put in place with the best intentions, often turn against their purpose. Think of regulations that limit the height of the ladders window cleaners are allowed to use in their work; the idea behind them is increasing the safety of those who clean windows. But it results in window cleaners having to resort to scaffolding or boom lifts more often; this makes their services much more expensive. With the result that people will try to clean their own windows. Without the experience that comes with the profession. This law is reported to only have resulted in an increase in window cleaning accidents… And boom lifts aren’t fail-proof either; I found seven cases of death and 19 of injury due to boom lift in the Netherlands since 2003.

Source: Aubrey Dale, Creative Commons

So well-meant laws often have a reverse effect. But could it work the other way? As I wrote in a blog post in early June; North Carolina was considering making it unlawful to base coastal protection policies on up-to-date sea level change research. This law didn’t make it; the House of Representatives have voted for its revision. The new version, which will have to get an OK from the governor before it becomes a law, contains the clause that the Coastal Resources Commission shall direct its Science Panel to actually study scientific literature, and come up with recommendations only after that. They have until December 2015 to write the report. So the threat of North Carolina making it unlawful to be informed about sea level change is gone. On the long term, that is. The new version also contains a clause that says, and I quote, “The Coastal Resources Commission and the Division of Coastal Management of the Department of Environment and Natural Resources shall not define rates of sea-level change for regulatory purposes prior to July 1, 2016.”

An example of coastal erosion from California

Science (the magazine) considers this bad news; those who wish to know if it’s wise to build a new house somewhere on the coast get no guidelines from their state for the next four years. But it also means they are allowed to think for themselves. If policy makers are forced to give out meaningless guidelines, it may well go unnoticed by the consumer of these guidelines that these are completely detached from reality. But when the state publicly announces silence on the topic, people will be quite aware they have to find out for themselves. And not everybody will be pleased that they pay their tax, but still have to spend time on making their own guidelines; and some people will undoubtedly find incomplete or inaccurate information in their search, but altogether I think it’s a much better situation than one in which it is downright illegal to do the sensible thing. So this revised law is a watered-down version of a law aimed at keeping the people ignorant; this version may serve to make them better informed that they were before!