GeoLog

GeoLog

Imaggeo on Mondays: Tasman Lake Down Under 

Imaggeo on Mondays: Tasman Lake Down Under 

The Tasman Glacier Terminal Lake, seen in this photograph, lies in the Aoraki Mount Cook National Park in New Zealand’s south island. The photographer, Martina Ulvrova, stated she “finally got to see the largest glacier in New Zealand after several days of heavy rain, during which the landscape was bathing in mist”.

The Tasman Glacier is 23 km long and is surrounded by a terminal proglacial lake with floating icebergs. The lake was only formed in the 1970s by the melting of the Tasman Glacier. Today the lake is 7 km long and growing faster than ever with its length that is increasing by approximately 180 m per year on average!

This continual lake growth is largely due to the receding glacier which has been retreating since the 1970s and has shrunk by approximately 6 km over the past fifty years. Blocks of ice regularly break-off the flowing glacier and float peacefully on the lake. One can see only the tips of these enormous icebergs with about 90% of the iceberg mass hidden below the surface of the water.

In 2011, after a 6.3 magnitude earthquake, 40 million tonne chunk of ice broke away from the Tasman glacier and plunged into the lake. The collapse of the gigantic block caused a local tsunami with waves as high as three meters bouncing from side to side across the lake for thirty minutes. Scientists expect the Tasman glacier to continue shrinking considerably and warn that it is likely to eventually disappear. Global warming has hit this secret paradise and predictions are alarming.

By Martina Ulvrova

If you pre-register for the 2018 General Assembly (Vienna, 08–13 April), you can take part in our annual photo competition! From 15 January until 15 February, every participant pre-registered for the General Assembly can submit up three original photos and one moving image related to the Earth, planetary, and space sciences in competition for free registration to next year’s General Assembly!  These can include fantastic field photos, a stunning shot of your favourite thin section, what you’ve captured out on holiday or under the electron microscope – if it’s geoscientific, it fits the bill. Find out more about how to take part at http://imaggeo.egu.eu/photo-contest/information/.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submittheir photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Geosciences Column: How fast are Greenland’s glaciers melting into the sea?

Geosciences Column: How fast are Greenland’s glaciers melting into the sea?

The Greenland ice sheet is undergoing rapid change, and nowhere more so than at its margins, where large outlet glaciers reach sea level. Because these glaciers are fed by very large reservoirs of ice, they don’t just flow to the coast, but can extend many kilometres out into the ocean. Here, the ice – being lighter than water – will float, but remain connected to the ice on the mainland. This phenomenon is called an ice shelf or, if it is confined to a relatively narrow fjord, an ice tongue. Ice shelves currently exist in Antarctica as well as in high Arctic Canada and Greenland.

Ice shelves already float on the ocean so that their melting does not affect sea level, but they are a crucial part of a glacier’s architecture. The mass of an ice shelf, as well as any contact points with fjord walls, mean that it acts as a buttress for the rest of the glacier, slowing down its flow speed and stabilising it. When ice shelves melt, therefore, this can lead to the whole glacier system behind them flowing faster and thus delivering more land-based ice to the ocean.

Ice shelves lose mass as icebergs calve off at their seaward end, and through melting on their surface – but, unlike glaciers on land, they are with the ocean below. This ice-ocean interface is an important source of melting for a number of glaciers in northern Greenland; instead of the large volume of icebergs produced by many glaciers further south, the large ice tongues reaching into the ocean mean that a lot of ice is instead lost through submarine melting.

This ice-ocean interface is an environment that was, until recently, very difficult to accurately observe and study, and accordingly there is relatively little data on the impact of submarine melting on ice shelves. But the changes that take place here, at the ice-ocean interface, can have important implications for the entire glacier system, as well as for the ice sheet as a whole.

Over the last 30 years, a number of Arctic ice shelves and ice tongues have dramatically shrunk or disappeared entirely. In the Canadian Arctic, the Ellesmere ice shelf broke up into a number of smaller shelves over the course of the 20th century, most of which are continuing to shrink. In Greenland, meanwhile, the dramatic retreat of the Jakobshavn Glacier’s ice tongue during the 2000s has been particularly well documented.

The largest remaining ice tongues in Greenland are now all located in the far north of the island. But even here, at nearly 80°N and beyond, ice tongues are changing rapidly. Warming air temperatures probably play a role in this development, but submarine melting is thought to be the key driver of these rapid changes.

Submarine melting of ice tongues thus appears to be an important variable in ice-sheet dynamics. A new study in the EGU’s open access journal The Cryosphere has now used satellite imagery to produce a detailed map of submarine melt under the three largest ice tongues in northern Greenland. They are the ones belonging to Petermann and Ryder Glaciers in far northwestern Greenland and 79N Glacier – named after the latitude of its location – in the northeast of the island. Each of these ice shelves extends dozens of kilometres from where the glacier stops resting on bedrock and begins to float (the so-called grounding line) and is up to several hundred metres thick.

The locations of Petermann (PG), Ryder (RG) and 79N Glaciers in northern Greenland. From Wilson et al. (2017).

Previous attempts to estimate submarine melt rates relied on an assumption of steady state: that the ice shelf is becoming neither thicker nor thinner. Given the recent changes in all these ice shelves and the glaciers above them, this is not a tenable assumption in this case. Petermann and Ryder Glaciers, in particular, have recently experienced large calving events that were probably related to unusual melt patterns under the waterline.

Lead author Nat Wilson, a PhD student at MIT and Woods Hole Oceanographic Institution, and his colleagues used satellite images spanning four years to create a number of digital elevation models of the Petermann, Ryder and 79N ice shelves. A digital elevation model, or DEM, is a three-dimensional representation of a surface created – in this case – from satellite-based elevation data. By comparing DEMs from different points in time to each other, the team could deduct changes in the height – and therefore volume – of the ice shelves. This method also allowed them to track visible features of the glaciers between images from different years, providing estimates of how fast the ice was flowing down into the ocean.

However, using digital elevation models in a marine setting is not always a straightforward matter. Tides can affect the elevation of ice shelves by a significant amount, especially as the distance from the grounding line increases, and their effect needed to be accounted for in the results. Similarly, the team had to account for the changes on the surface of the ice shelf, where snowfall and melting can affect its volume.

What Wilson and his colleagues were left with was a map of melt rates across the ice shelves. In some respects, the findings were unsurprising. Melt rates were greatest near the coast, where the ice shelves were thickest, because at these points they would be in contact with the ocean at depths of several hundred metres. At such depths, fjords around Greenland often contain warm, dense water that flows in from the continental shelf and contributes to rapid ice melt. As the ice shelves thin towards their outer edges, they are in contact with shallower, colder water that doesn’t melt the ice as quickly.

Submarine melt rates at Greenland’s largest ice tongues are shown in colour shading; the arrows show the direction of ice flow. PG – Petermann Glacier; RG -Ryder Glacier. From Wilson et al. (2017).

All three ice shelves lost between 40-60m per year to submarine melting at their thickest points, while this decreased to about 10m per year in thinner sections. This equates to billions of tonnes of ice melting in contact with the ocean. Each of the ice shelves lost at least five times as much ice to melting underwater than to melting on the surface. This highlights what an important contribution submarine melting makes to the mass balance of Greenland’s ice shelves, and that this remote environment is deserving of our interest and study.

The team found that at Ryder Glacier’s ice shelf, mass loss from melting (from both above and below) is not significantly greater than the amount of ice entering the ice shelf from land: the ice shelf appears to be relatively stable for the time being. The situation is similar at Petermann Glacier, although its ice shelf has been in rapid retreat and lost some 250 km in the decade leading up to 2010. With the extra submarine melting from that area, melting would likely have exceeded incoming ice! It remains to be seen whether Petermann Glacier and its ice shelf will stabilise in their new configuration.

Finally, at 79N Glacier, the results indicate the ice shelf is losing mass faster than it is replenished from upstream. The ice tongue loses some 1.3% of its mass to melting each year – and that’s before iceberg calving is included in the equation. This finding is consistent with satellite imagery that suggests that the ice shelf at 79N has been thinning in recent decades.

This new study shows that there is considerable variability in submarine melting of ice shelves, both in space and in time. 79N glacier’s ice shelf – the biggest one remaining in Greenland – exhibited the highest mass deficit in this study, suggesting that we may see major changes in this glacier in future. With this type of melt making up for the bulk of mass loss of northern Greenland’s ice shelves, its accurate prediction plays an important role in understanding how these huge glaciers – and the whole ice sheet itself – will change in coming years.

By Jon Fuhrmann, freelance science writer

References

Wilson, N., Straneo, F., and Heimbach, P.: Satellite-derived submarine melt rates and mass balance (2011–2015) for Greenland’s largest remaining ice tongues, The Cryosphere, 11, 2773-2782, https://doi.org/10.5194/tc-11-2773-2017, 2017.

Hodgson, D. A. First synchronous retreat of ice shelves marks a new phase of polar deglaciation. Proc. Natl. Acad. Sci. U. S. A. 108, 18859-18860, doi:10.1073/pnas.1116515108 (2011).

Münchow, A., L. Padman, P. Washam, and K.W. Nicholls. 2016. The ice shelf of Petermann Gletscher, North Greenland, and its connection to the Arctic and Atlantic OceansOceanography 29(4):84–95, https://doi.org/10.5670/oceanog.2016.101.

Reeh N. (2017) Greenland Ice Shelves and Ice Tongues. In: Copland L., Mueller D. (eds) Arctic Ice Shelves and Ice Islands. Springer Polar Sciences. Springer, Dordrecht. https://doi.org/10.1007/978-94-024-1101-0_4

Truffer, M., and R. J. Motyka, Where glaciers meet water: Subaqueous melt and its relevance to glaciers in various settings, Rev. Geophys., 54, 220– 239. doi:10.1002/2015RG000494,  (2016)

Migrating scientists

Migrating scientists

Scientific research is no doubt enriched by interdisciplinarity and collaborations which cross borders. This, combined with the scarcity of academic positions and the need to further ones horizons by experiencing varied research environments, leads many scientists to relocate (if only on a short term basis) to a country which is not their own.  In today’s post, freelance science writer Robert Emberson explores the pros and cons of the nomadic lifestyle many researchers find themselves embracing in order to forward their work.

Scientists can consider themselves a lucky group of people. Having colleagues across the world working passionately at advancing the spectrum of human knowledge offers more opportunities to collaborate across national borders than perhaps any other field of human endeavour. Working with researchers of different nationalities is a chance to share ideas and experience; more often than not, the whole is greater than the sum of its parts.

In many cases though, this collaboration requires scientists to move their whole lives, temporarily or permanently, to new countries. Research on a given topic is almost never focused in one geographic region, and so a significant minority of scientists leave their homeland to pursue their careers. In September this year, the Twitter account @realscientists started a discussion about the implications of this movement, under the hashtag #migratingscientists. Many researchers shared inspirational and personal tales about their peripatetic lifestyles, and these brief snippets serve as a useful insight into the disruptive nature of crossing borders for work.

What are the deeper lessons we can take from scientists who migrate for work? What impact does it have on their scientific, and personal lives?

A recent analysis of published studies has suggested that migrating might well improve the career prospects of scientists. Sugimoto and colleagues analysed the citation scores of 14 million papers (between 2008 and 2015) from 16 million authors, and found that, in general, those written by scientists who moved country during that time have citation scores 40% higher than those by authors who remained put. Surprisingly, despite a perception that international collaboration is widespread, only 4% of the scientists in the dataset moved during the window of observation.

The perception of extensive movement for researchers may be coloured by science in the English-speaking world. Foreign-born researchers make up 27% of scientists or engineers in the USA, and 13% in the UK. These countries seem to benefit significantly in terms of the impact of the research produced within their borders; countries with greater mobility tend to produce more highly cited papers. It’s a mutually beneficial relationship, at least in terms of citations, and moreover researchers returning home can bring with them a wider network of colleagues, potentially boosting research and development in their own countries.

I spoke to the lead author, Professor Sugimoto, about these trends, and she told me that much of it comes down to what is available in these countries.

“Scholars do best when they have access to resources (personnel, infrastructure, and materials)”, she says. “Countries with high scientific capacity and investment also tend to have a critical mass of scholars. Collaboration has been linked to higher production and citation, so it is no surprise that those with access to enlarge their network are likely to be successful on these metrics.”

The US and UK are two countries where open borders are increasingly under attack. Immigration is always a hot-button topic, and while in both countries an opposition to immigration is not necessarily new, increased restrictions on immigration are now more likely with a Republican-led government in the US and Brexit in the UK. Already there are suggestions that researchers are increasingly looking elsewhere for positions; based on the studies, this could lead to a decline in the impact of research from these countries.

As shown by Prof Sugimoto and colleagues, scientists don’t exactly fit into the standard definition of immigrant. The researchers point toward mobility, rather than migration, as the important descriptive term here. Scientists tend to return to their home country after spending time abroad, and as such represent temporary migrants, rather than permanent. Social attitudes towards skilled workers tend to be different to those surrounding long-term immigrants and it would benefit researchers if policymakers went out of their way to emphasise that scientists fit into this category.

According to Professor Sugimoto, the short-term nature of mobility is what is most beneficial.

“Unless these scholars maintain ties with their home countries, emigration is likely to yield to deficits for other countries. Circulation, on the other hand, should yield benefits for all countries. Short-term stays can establish ties and provide an influx of resources, without necessarily removing scholars from their home networks.”

Treating scientists as visiting experts, then, is perhaps a more productive way forward.

But immigration visas and increases in citation indices are just one side of the story for scientists. Reading through some of the tweets tagged with #migratingscientists, many focus on the upheaval of their personal lives, for better or worse. It’s sometimes too easy to think about researchers as ‘human capital,’ but each of those humans have personal connections and a definition of home. Some studies suggest that foreign-born researchers may be more productive than their home-grown counterparts, but their satisfaction with life tends to be lower. What’s the deal?

Maslow’s hierarchy of needs, a framework commonly used in sociology to understand the different human requirements and personal development, suggests that the human need for Belonging is more fundamental than the requirement for Self-fulfilment. In other words, before researchers can genuinely accomplish their best work, they have a more basic need for a network of friends and family to belong to, or a place to call home. Finding this sense of belonging can be tricky in a foreign country. Language barriers can make it a struggle to meet new friends, and cultural tropes and mores may be more difficult to transcend than it first seems too, particularly when attitudes towards the researcher’s race or gender differ.

Early career researchers on short-term contracts may also struggle to maintain a sense of belonging to a particular place; extensive travel and fieldwork can exacerbate this. As a PhD student, living in a foreign country and travelling for labwork, field campaigns and conferences I sometimes felt like George Clooney’s character in the film Up in the Air, where he struggles with a life lived out of a backpack and in airport lounges.

Migrating scientists must make choices about close personal relationships; should they leave a partner behind or try to make it work long-distance? It’s doubly difficult to find positions for two people, let alone moving a more extended family. Many of the stories on twitter stress the importance of supportive partner or family.

Pay may also be lower for foreign-born scientists, too. Despite their outsize contribution to research output, foreign scientists in the US may be paid less than their peers, both in terms of salary, and the availability of funding sources. These hurdles make an already tricky transition to a new country significantly harder.

So it seems the research impact on a national and individual scale may benefit from increased mobility of researchers, but at the same time the personal tribulations may make this a challenge for many scientists.

How do scientists weigh up these pros and cons? Well, if Twitter is anything to go on, they’re clearly an enthusiastic bunch of folks, since many of the stories tend to emphasise the fun had along the way, as well as the positive experiences.

Given that these nitty-gritty questions about personal experience are unsurprisingly hard to quantify, our understanding of the impact of mobility on scientists personal lives is often based on these kind of anecdotes; it would be greatly beneficial to survey researchers more widely to ascertain what kind of systematic effects migration induces. A more qualified comparison with the citation-based indices would then be feasible.

For now, even if removing the obstacles to scientists moving across borders may raise questions amongst some policymakers, it would reduce the negative connotations of migrating for research – which might allow for wider collaboration, and a more effective global body of scientists.

By Robert Emberson, freelance science writer

Editor’s note: This is a guest blog post that expresses the opinion of its author, whose views may differ from those of the European Geosciences Union. We hope the post can serve to generate discussion and a civilised debate amongst our readers.

Imaggeo on Mondays: Robberg Peninsula – a home of seals

Imaggeo on Mondays: Robberg Peninsula – a home of seals

This picture is taken from the Robberg Peninsula, one of the most beautiful places, and definitely one of my favorite places in South Africa. The Peninsula forms the Robberg Nature Reserve and is situated close to the Plettenberg Bay on the picturesque Garden Route. “Rob” in Dutch means “seal”, so the name of the Peninsula is translated as “the seal mountain”. This name was given to the landmark by the early Dutch mariners, who observed large colonies of these noisy and restless animals on the rocky cliffs of the Peninsula. Seals still inhabit this area today.

The Peninsula is constituted of two rocky parts, rising above the sea level at about 150 m, and which are separated from each other by the “Gap” – a low and narrow sandy neck. The length of the Peninsula is about 4 km and the width is up to 750 m, which narrows down to 200 m at the “Gap”. The eastern rocky part forms an extension to the south – another tiny peninsula, “the Island” (on the picture). “The Island” is a small rocky area connected with the main Peninsula by a narrow strip of sand. This sand bar is essentially a beach washed by water at its both long sides. With “the Island” the entire Peninsula has a shape of a mitten, which thumb is looking down.

Robberg Island is entirely built up by the sedimentary rocks: quartzites of the Table Mountain Group (part of the Cape Supergroup), and Robberg’s Formation sandstones, conglomerates and breccias. Table Mountain Group is formed some 500-330 million years ago; and the Robberg’s formation, which is the part of the Uitenhage Group, is around 120 million years old and related to Gondwana break-down. Upper parts of the Peninsula are covered by the Quaternary dune deposits. At the moment the rocks of Robberg Peninsula are actively eroded by the Indian Ocean waters.

Robberg Peninsula is a beautiful home of many marine bird species, small reptiles, seals and indigenous plants. The Nelson Bay Cave, situated on the Robberg Peninsula, is one of the oldest caves, inhabited by human. It was occupied from 120 000 years ago, by various tribes, including San and Khoikhoi people. Nelson Bay Cave was formed due to the erosion caused by the ocean waves.

Description by Elizaveta Kovaleva, post-doctoral researcher at University of the Free State, in South Africa

If you pre-register for the 2018 General Assembly (Vienna, 08–13 April), you can take part in our annual photo competition! From 15 January until 15 February, every participant pre-registered for the General Assembly can submit up three original photos and one moving image related to the Earth, planetary, and space sciences in competition for free registration to next year’s General Assembly!  These can include fantastic field photos, a stunning shot of your favourite thin section, what you’ve captured out on holiday or under the electron microscope – if it’s geoscientific, it fits the bill. Find out more about how to take part at http://imaggeo.egu.eu/photo-contest/information/.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.