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Imaggeo on Mondays: Concord at midnight

Imaggeo on Mondays: Concord at midnight

The high peaks of the Alps are always awe inspiring, but this midnight shot, captured by Alessandro Lechmann, a PhD student at the Institute of Geological Sciences at the University of Bern, further enhance their fragile beauty. With a warming climate threatening snow availability to even the highest peaks, it has never been more important to appreciate the importance of the glaciers which drape the mountain slopes.

This photograph shows a view from the Jungfraujoch (a saddle in the Bernese Alps, connecting the two four-thousander peaks Jungfrau and Mönch, at an elevation of 3,466 metres above sea level) towards the south-east down the Jungfraufirn (an arm of the Great Altesch Glacier).

Originating amidst three of the most famous mountains of the Swiss Alps (Eiger, Mönch and Jungfrau), this glacier flows southwards towards the Concordiaplatz, where it merges with the Ewigschneefäld and the Great Aletschfirn into the Great Aletsch Glacier. Even today, despite reports of receding glaciers in the Alps, it forms the largest and longest Alpine glacier.

In the countries surrounding the Alps, glacial landforms dominate the landscape. From drumlins, moraines (accumulations of glacial debris) and overdeepenings in the foreland to U-shaped valleys (Lauterbrunnen is a marvellous example) and cirques in mountainous regions. Although retreating at rates not seen previously, these glaciers carved the face of central Europe during the last glacial-interglacial cycles.

The building of the railway to the Jungfraujoch research station started in 1896 and was completed in 1912; an impressive feat considering the limited technology before the First World War. Perched precariously 3500 m above sea level, the research station (known for its prominent sphinx observatory), has contributed significantly   to the understanding of the atmospheric sciences, glaciology and cosmic ray physics.

The ridge which the Jungfraujoch is built on, marks the northern margin of the exposed crystalline core of the Alpine orogeny. Interestingly, this mountain ridge, in addition to being a geological boundary, is also a major watershed. Rain that falls north, flows via the Aare into the Rhine, which eventually discharges into the North Sea. Precipitation on the southern flank and melt water from the Jungfraufirn, on the other hand, joins the Rhone in the Valais valley, that ends up in the Mediterranean Sea. This highlights the importance of Alpine glaciers as a water stores which continue to provide water throughout the year.

By Alessandro Lechmann PhD student at the Institute of Geological Sciences at the University of Bern

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/.

Geosciences Column: How El Niño triggered Indonesia corals die-off

Geosciences Column: How El Niño triggered Indonesia corals die-off

In the glistening waters of Indonesia, shallow corals – the rain forests of the sea – teem with life.  Or at least they did once. Towards the end of 2015 the corals started to die, leaving a bleak landscape behind. An international team of researchers investigated the causes of the die-off. Their findings, published recently in the EGU’s open access journal, Biogeosciences, are rather surprising.

Globally, corals face tough times. Increasing ocean-water temperatures (driven by a warming climate) are disrupting the symbiotic relationship between corals and the algae that live on (and in) them.

The algae, known as zooxanthellae, provide a food source for corals and give them their colour. Changing water temperatures and/or levels, the presence of contaminants or overexposure to sunlight, put corals under stress, forcing the algae to leave. If that happens, the corals turn white – they become bleached – and are highly susceptible to disease and death.

Triggered by the 2015-2016 El Niño, water temperatures in many coral reef regions across the globe have risen, causing the National Oceanic and Atmospheric Administration (NOAA) to declare the longest and most widespread coral bleaching event in recorded history. Now into its third year, the mass bleaching event is anticipated to cause major coral die-off in Australia’s Great Barrier Reef for the second consecutive year.

The team of researchers studying the Indonesian corals found that, unlike most corals globally, it’s not rising water temperatures which caused the recent die-off, but rather decreasing sea level.

While conducting a census of coral biodiversity in the Bunaken National Park, located in the northwest tip of Sulawesi (Indonesia), in late February 2016, the researchers noticed widespread occurrences of dead massive corals. Similar surveys, carried out in the springs of 2014 and 2015 revealed the corals to be alive and thriving.

In 2016, all the dying corals were found to have a sharp horizontal limit above which dead tissue was present and below which the coral was, seemingly, healthy. Up to 30% of the reef was affected by some degree of die-off.

Bunaken reef flats. (a)Close-up of one Heliopora coerula colony with clear tissue mortality on the upper part of the colonies; (b)same for a Porites lutea colony; (c) reef flat Porites colonies observed at low spring tide in May 2014. Even partially above water a few hours per month in similar conditions, the entire colonies were alive. (d) A living Heliopora coerula (blue coral) community in 2015 in a keep-up position relative to mean low sea level, with almost all the space occupied by corals. In that case, a 15 cm sea level fall will impact most of the reef flat. (e–h) Before–after comparison of coral status for colonies visible in (c). In (e), healthy Poritea lutea (yellow and pink massive corals) reef flat colonies in May 2014, observed at low spring tide. The upper part of colonies is above water, yet healthy; (f) same colonies in February 2016. The white lines visualize tissue mortality limit. Large Porites colonies (P1, P2) at low tide levels in 2014 are affected, while lower colonies (P3) are not. (g) P1 colony in 2014. (h) Viewed from another angle, the P1 colony in February 2016. (i) Reef flat community with scattered Heliopora colonies in February 2016, with tissue mortality and algal turf overgrowth. Taken from E. E. Ampou et al. 2016.

The confinement of the dead tissue to the tops and flanks of the corals, lead the scientists to think that the deaths must be linked to variations in sea level rather than temperature, which would affect the organisms ubiquitously. To confirm the theory the researchers had to establish that there had indeed been fluctuations in sea level across the region between the springs of 2015 and 2016.

To do so they consulted data from regional tide-gauges. Though not located exactly on Bunaken, they provided a good first-order measure of sea levels over the period of time in question. To bolster their results, the team also used sea level height data acquired by satellites, known as altimetry data, which had sampling points just off Bunaken Island. When compared, the sea level data acquired by the tidal gauges and satellites correlated well.

Sea-level data from the Bitung (east North Sulawesi) tide-gauge, referenced against Bako GPS station. On top, sea level anomalies measured by the Bitung tide-gauge station (low-quality data), and overlaid on altimetry ADT anomaly data for the 1993– 2016 period. Note the gaps in the tide-gauge time series. Middle: Bitung tide-gauge sea level variations (high-quality data, shown here from 1986 till early 2015) with daily mean and daily lowest values. Bottom, a close-up for the 2008–2015 period. Taken from E. E. Ampou et al. 2016.

The data showed that prior to the 2015-2016 El Niño, fluctuations in sea levels could be attributed to the normal ebb and flow of the tides. Crucially, between August and September 2015, they also showed a sharp decrease in sea level: in the region of 15cm (compared to the 1993-2016 mean). Though short-lived (probably a few weeks only), the period was long enough that the corals sustain tissue damage due to exposure to excessive UV light and air.

NOAA provides real-time Sea Surface Temperatures which identify areas at risk for coral bleaching. The Bunaken region was only put on alert in June 2016, long after the coral die-off started, therefore supporting the crucial role sea level fall played in coral mortality in Indonesia.

The link between falling sea level and El Niño events is not limited to Indonesia and the 2015-2016 event. When the researchers studied Absolute Dynamic Topography (ADT) data, which provides a measure of how sea level has change from 1992 to 2016, they found sea level falls matched with El Niño years.

The results of the study highlight that while all eyes are focused on the consequences of rising ocean temperatures and levels triggered by El Niño events, falling sea levels (also triggered by El Niño) could be having a, largely unquantified, harmful effect on corals globally.

By Laura Roberts Artal, EGU Communications Officer

References and resources

Ampou, E. E., Johan, O., Menkes, C. E., Niño, F., Birol, F., Ouillon, S., and Andréfouët, S.: Coral mortality induced by the 2015–2016 El-Niño in Indonesia: the effect of rapid sea level fall, Biogeosciences, 14, 817-826, doi:10.5194/bg-14-817-2017, 2017

Varotsos, C. A., Tzanis, C. G., and Sarlis, N. V.: On the progress of the 2015–2016 El Niño event, Atmos. Chem. Phys., 16, 2007-2011, doi:10.5194/acp-16-2007-2016, 2016.

What are El Niño and La Niña? – a video explainer by NOAA

Coral Reef Watch Satellite Monitoring by NOAA

Global sea level time series – global estimates of sea level rise based on measurements from satellite radar altimeters (NOAA/NESDIS/STAR, Laboratory for Satellite Altimetry)

El Niño prolongs longest global coral bleaching event – a NOAA News item

NOAA declares third ever global coral bleaching event – a NOAA active weather alert (Oct. 2015)

The 3rd Global Coral Bleaching Event – 2014/2017 – free resources for media and educators

What is coral bleaching? – an infographic by NOAA
The ENSO (El Niño–Southern Oscillation) Blog by Climate.gov (a NOAA resource)

February GeoRoundUp: the best of the Earth sciences from around the web

Comparing the TRAPPIST-1 planets

Drawing inspiration from popular stories on our social media channels, as well as  unique and quirky research news, this monthly column aims to bring you the best of the Earth and planetary sciences from around the web.

Major story

Undoubtedly the story of the month is the discovery of a star system of seven Earth-sized planets just 40 light-years away from our own. What makes the finding so exciting is that three of the planets lie in the habitable zone. All could have oceans and atmospheres, making them good candidates to search for extraterrestrial life.

The seven Earth-sized worlds orbit the ultra-cool dwarf star, TRAPPIST-1, which has been known to astronomers for some time. As the planets passed in front of TRAPPIST-1, the star’s light output dipped. Using a combination of ground and spaced based telescopes, the changes in the light output were used to detect the planets and gather information about their size, composition and orbit, explains the press release by the European Southern Observatory.

This simple GIF by New Scientist illustrates the principle of how the remarkable planets were found (while at the same time highlighting the fact there is a mind-blowing number of exoplanets scattered throughout space!).

The ultra-cool dwarf star and its planetary system has an even cooler website, which comes complete with great posters, videos, short stories, poems and graphic novels; as well as a detailed timeline of all the years of work which took place behind the scenes and culminated in the announcement made earlier this month.

Our top pick for a science poem honouring the discovery is In Search of New Life by Sam Illingworth, a lecturer at Manchester Metropolitan University.  You can also find an audio version of the poem here.

Far into space, amongst the darkest Sea

New planets sit like marbles in a row.

We turn our eyes to find out what might be

And search for patterns in their ether’s flow;

Then try to see what else might lie below.

And as we probe how life’s rich web was spun,

Do they look back towards our distant sun?

 

What you might have missed

The discovery of a previously unknown continent below New Zealand and New Caledonia dominated headlines towards the middle of the month.

Dr. Mortimer, of GNS Science and lead author of the study, argues that “being more than 1 million square kilometers in area, and bounded by well-defined geologic and geographic limits, Zealandia [the name given to the newly discovered continent] is, by our definition, large enough to be termed a continent.”

But without an official authority which designates the existence of continents, it will be for the broader scientific community to recognise Zealandia as one. And the jury is still out, as Alex Witze finds in this Nature News & Comment article:

“Claiming that Zealandia is a continent is a bit like stamp collecting,” says Peter Cawood, a geologist at Monash University in Melbourne, Australia. “So what?”

While the (potentially) new Antipodean continent dominated headlines, you might have missed the discovery of another lost continent. Deep under the waters of the Indian Ocean, sandwiched between Madagascar and India, lie the scattered pieces of an ancient, drowned, microcontient called Mauritia. The authors of the study, published earlier this month in Nature Communications, dated zircons of up to 3 billion years old from Mauritanian volcanic rocks. Considering Mauritania is much younger, the researchers argue the zircons must have come from another, already existing continent.

Meanwhile, in the southern-most reaches of our planet, a huge iceberg is set to breakaway from the Larsen C Ice Shelf, on the northeastern coast of the Antarctic Peninsula. A large crack in the ice was spotted in natural-colour satellite imagery captured by NASA back in August 2016. Int January 2017 alone, the crack grew by more than 10 km in length and now stretches 175 km over the ice.

British Antarctic Survey (BAS) scientists recently captured footage of the huge crack. The video highlights what the calving of such a large iceberg might mean for the Larsen C ice shelf, while this Nature News and Comment story highlights how far glaciology has come since similar calving events in the 90s and 00s. Scientists now have a much better understanding of what might happen in the weeks and months to come.

Five links we liked

The EGU story

After long-awaited snowfall in January, parts of the Alps are now covered with fresh powder and happy skiers. But the Swiss side of the iconic mountain range had the driest December since record-keeping began over 150 years ago, and 2016 was the third year in a row with scarce snow over the Christmas period. A study published this month in The Cryosphere, a journal of the European Geosciences Union, shows bare Alpine slopes could be a much more common sight in the future.

The new research, by scientists based at the Institute for Snow and Avalanche Research (SLF) and at the CRYOS Laboratory at the École Polytechnique Fédérale in Switzerland, shows that the Alps could lose as much as 70% of snow cover by the end of the century. However, if humans manage to keep global warming below 2°C, the snow-cover reduction would be limited to 30% by 2100.

And don’t forget! To stay abreast of all the EGU’s events and activities, from highlighting papers published in our open access journals to providing news relating to EGU’s scientific divisions and meetings, including the General Assembly, subscribe to receive our monthly newsletter.

Imaggeo on Mondays: a storm is coming

Imaggeo on Mondays: a storm is coming

Coastlines globally are immensely diverse: from the beautifully topical and sun kissed beaches of the Caribbean, to the wet and misty British coastline, through to the raw and wild Alaskan shores, they are home to scores of flora and fauna; rich habitats shaped by powerful forces of nature.

In stark contrast, some coastlines, (28,000 km worldwide to be precise) are dry almost barren places, where little grows. These long stretches of inhospitable seaside lands are known as hyperarid and arid coastlines. Due to the lack of protective vegetation the land is exposed to the action of winds and the sun, leaving behind pavements of bare rock, large dune formations and/or highly saline enclosed lakes (sebkhas).

The Gulf of Aqaba, in the north-western tip of Saudi Arabia, where the desert meets the Red Sea is one such place. Rivers here, which drain into the sea water, are fleeting. They appear after heavy rainfall, when flash floods deliver huge influxes of sediment to the coral-rich waters of the Red Sea.

Nadine Hoffman took today’s featured image while driving from Israel from the Red Sea. Pictured is the northern tip of Saudi Arabia, where a spring storm is coming into the desert bringing severe rain and flash floods. Eventually, the flood waters will drain into the Gulf of Aqaba.

 

If you pre-register for the 2017 General Assembly (Vienna, 22 – 28 April), you can take part in our annual photo competition! From 1 February up until 1 March, 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/.

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