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Cryospheric Sciences

Imaggeo on Mondays: Late Holocene Fever

Imaggeo on Mondays: Late Holocene Fever

A huge ice fall off the Perito Moreno glacier in the Los Glaciares National Park, southwest Santa Cruz Province, Argentina, was voted one of the three best pictures entered into the EGU’s annual photo contest, by the conference participants at the 2015 General Assembly.

Perito Moreno glacier is one of 48 glaciers feeding into the Southern Patagonia ice field, which combined with the Northern Patagonia ice field, comprise the largest temperate ice mass in the Southern Hemisphere. Like many other mountain glaciers, Perito Moreno, is highly sensitive to climate change. At the surface of a glacier, erosive processes know as ablation, can remove ice from the bulk of the glacial mass. If the ice lost is not replaced in sufficient quantities by rainfall and snow provided by weather systems, the energy balance of the glacier is upset and the glacier starts to shrink. At the glacial surface, the processes of accumulation and ablation, clearly manifest the strict connection between glaciers and climate.

In a recent interview, Bernard Francou, a renowned French glaciologist, explained that glacier depletion in the Andes region has increased dramatically in the second half of the 20th century. In recent decades the glacier recession rates increased at an unprecedented rate when compared to the last the last three centuries. It is estimated that glaciers in this region have lost between 35% and 50% of their area and volume since 1976.

Christian Massari, a hydrology postdoctoral researcher of the Italian National Research Council, says “capturing the precise moment when the large chunk of ice broke off the glacier front was not easy task. It required concentration to patiently wait two hours, on a hot January day, to capture the critical moment.”

You can watch a video of a similar ice fall event, which took place in January 2012, here.

Southern Patagonia Ice Field. Credit: Astronaut photograph ISS038-E-47324 was acquired on February 13, 2014, with a Nikon D3S digital camera using a 65 millimeter lens, and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. The image was taken by the Expedition 38 crew. It has been cropped and enhanced to improve contrast, and lens artifacts have been removed.

Southern Patagonia Ice Field . Credit: Astronaut photograph ISS038-E-47324 was acquired on February 13, 2014, with a Nikon D3S digital camera using a 65 millimeter lens, and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. The image was taken by the Expedition 38 crew. It has been cropped and enhanced to improve contrast, and lens artifacts have been removed. (Distributed via Nasa Earth Observatory, Image of the Day ).

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/.

Imaggeo on Mondays: Sunset over the Labrador Sea

Ruby skies and calm waters are the backdrop for this week’s Imaggeo image – one of the ten finalist images in this year’s EGU Photo contest.

 Sunset over the Labrador Sea. Credit: Christof Pearce (distributed via  imaggeo.egu.eu)

Sunset over the Labrador Sea. Credit: Christof Pearce (distributed via imaggeo.egu.eu)

“I took the picture while on a scientific cruise in West Greenland in 2013,” explains Christof Pearce, a postdoctoral researcher at Stockholm University. “We spent most of the time inside the fjord systems around the Greenland capital, Nuuk, but this specific day we were outside on the shelf in the open Labrador Sea. The black dot on the horizon toward the right of the image is a massive iceberg floating in the distance.”

Pearce took part in a research cruise which aimed to obtain high-resolution marine sedimentary records, which would shed light on the geology and past climate of Greenland during the Holocene, the epoch which began 11,700 years ago and continues to the present day.

A total of 12 scientists and students took part in the Danish-Greenlandic-Canadian research cruise in the Godthåbsfjord complex and on the West Greenland shelf. By acquiring cores of the sediments at the bottom of the sea floor, the research team would be able to gather information such as sediment lithology, stable isotopes preserved in fossil foraminifera – sea fairing little creatures – which can yield information about past climates, amongst other data. One of the main research aims was to learn more about the rate at which the Greenland Ice Sheet melted during the Holocene and how this affected local climate conditions and the wider climate system.

“The picture was taken approximately 25 kilometres off the shore of west Greenland coast. In this region the water depth is ca. 500 meters,” describes Pearce. “At this location we deployed a so-called gravity corer and took a 6 meter long sediment core from the ocean floor. Based on radiocarbon measurements – by measuring how much carbon 14 is left in a sample, the age of the sampled units can be known – we now know that these 6 meters correspond to approximately 12000 years of sedimentation, and thus it captures a history of climate and oceanography from the last ice age all the way to present day.”

 

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/.

Imaggeo on Mondays: Just Passing

Imaggeo on Mondays: Just Passing

If lucky enough to visit Ilulissat Icefjord, you’d find yourself in a truly ancient landscape. From the up to 3.9 billion year old Precambrian rocks, to ice dating back to the Quaternary Ice Age (2.6 thousand years old) and archaeological remains which evidence the past settlement of this remote Greenlandic outpost, it’s no surprise this stunning location has been declared a UNESCO world heritage site.

Today’s Imaggeo on Mondays photograph was taken by Camille Clerc, at Sermermiut, an old inuit settlement at the mouth of the Ilulissat Icefjord. Located 1,000 km up the west coast of Greenland, in the Bay of Disko Bugt, 250 km inside the Arctic Circle, the icefjord is the sea mouth of Jakobshavn Glacier – one of the few glaciers on Greenland which reaches the sea. Confined either side by ancient Precambrian rocks, the icefjord forms a narrow, 3-6 km wide tidewater ice-stream, where vast amounts of meltwater and ice from the Greenland ice-sheet reach the sea.

Jakobshavn (also known as Sermeq Kujalleq) is Greenland’s fastest moving glacier. Huge chunks of ice break off the glacier front via Ilulissat Icefjord in a process known as glacier calving. Annually, over 35 km3 of ice is calved into the sea; equivalent to 10% of the production of all Greenland calf ice and more than any other glacier outside Antarctica! As a result, there is an almost constant production of icebergs, which vary in size from small lumps to bergs which can exceed 100m height. As they make their way towards the sea, the icebergs actively erode the fjord bed, slowly changing its morphology over time.

The tragic sinking of the Titanic on its maiden voyage, as a result of a collision with an iceberg on the night of the 15th April 1912, is part of modern history and was even portrayed in a Hollywood blockbuster. Could one of the mighty icebergs calved from Jakobshavn via Ilulissat Icefjord, be the culprit of the sinking of the White Star Line vessel? Pinpointing the exact location from which the glacier was calved is tricky. Most icebergs found in North Atlantic waters originate from the western coast of Greenland. They are pushed slowly towards more northerly latitudes by the West Greenland Current and then forced towards the Atlantic, hugging the coast of Canada, by the Labrador Current, eventually making their way to the Gulf Stream, along one of the world’s busiest shipping routes. The journey there is long and more often than not, the icebergs take such battering during the voyage that their original size is much diminished.

 

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/.

Geoscience Column: Recent and future changes in the Greenland Ice Sheet

Geoscience Column: Recent and future changes in the Greenland Ice Sheet

Over the past few decades, the Arctic region has warmed more than any other on Earth. The Greenland Ice Sheet is losing mass faster than ever before, and is expected to keep melting with consequences for global sea-level rise and ocean circulation. At a media briefing, during the EGU’s General Assembly in April (stream it here), researchers presented new results on the factors that influence the Greenland Ice Sheet’s rapid and profound changes – from glacial lakes to clouds and snow darkening.

The vast expanse of the Greenland Ice Sheet covers an area of 1.71 million km2 (approximately a tenth of the size of Russia), and holds a staggering volume of ice: 2.85 million km3. The ice sheet is only rivalled in size by one other: the Antarctic Ice Sheet. Scientist have calculated that the Greenland Ice Sheet stores enough freshwater to raise sea level by 7.4m, should all the ice melt, so understanding what causes the ice to melt now and in the future is critical!

The importance of clouds

When you think of clouds, you probably think of them as purveyors of rain and bad weather. But that is not all; clouds form an intrinsic part of the climate system which is more complex than simply how they affect day to day weather. In Greenland, (as elsewhere across the globe), clouds are a source of precipitation, bringing all-important snow which accumulates on the ice sheet and makes it grow in size.

Southern Tip of Greenland.  Satellite Image by  NASA. Source: Wikimedia Commons

Southern Tip of Greenland. Satellite Image by NASA. Source: Wikimedia Commons

Clouds also affect temperatures: on a clear day you’ll feel the warmth of the sun on your back, but as night falls temperatures start dropping quickly as heat is lost to the atmosphere. However, if in the late afternoon the clouds started rolling in, the night would be warmer, as clouds stop heat being lost to the atmosphere. If they stick around long enough though, they promote cooling, as they reflect sunlight away from the Earth’s surface.

“On a global scale, clouds (on average) tend to cool the Earth’s surface, but there are many regional differences”, explained Kristof Van Tricht,(a PhD student at the University of Leuven in Belgium), during the press conference.

It turns out that, in Greenland, the warming effect of clouds dominates, and warming of the surface encourages melting of the ice sheet. However, the remoteness of the area means that direct observations of just how much the clouds warm the surface and to what extent this impacts on the ice sheet has been limited. Until now.

Using satellite observations, Van Tricht and his team have been able to study the warming effect of clouds in more detail than ever before. Their models show that, in the presence of clouds, the Greenland Ice Sheet can be up to 1.2°C warmer, which can cause substantial melting. Compared to models ran without cloud cover, the ice sheet could melt up to 38% more. This equates to 12% more runoff from the ice sheet into the oceans, solely due to the presence of clouds.

Predictions of what the findings mean for the ice sheet in the future are tricky though. The scientists’ model is based on real-time observations and so it isn’t possible to look into the future. For that, improved cloud model simulations are needed.

Beautiful lakes

Lakes form, seasonally, on the surface of the Greenland Ice Sheet as a result of run-off water pooling in depressions in the ice. Although beautiful to look at, because they are darker than the surrounding ice, they attract more heat. The lakes also drain sporadically, and when they do, some of the water they hold drains through the ice making its way to the base of the ice sheet. Once there, the water lubricates the base of the ice sheet and promotes it to flow more easily and quickly towards the ocean. Combined, these two effects affect the dynamics of the ice sheet.

 Drained Supraglacial Lake Bed. This lake has drained through the bottom for several years in a row. The large block was initially formed in summer of 2006, but large cracks run through it from subsequent lake drainages.  Credit: Ian Joughin (distributed via  imaggeo.egu.eu )

Drained Supraglacial Lake Bed. This lake has drained through the bottom for several years in a row. The large block was initially formed in summer of 2006, but large cracks run through it from subsequent lake drainages.
Credit: Ian Joughin (distributed via imaggeo.egu.eu )

At present, the lakes generally form within the ablation zone – the low-altitude regions towards the edges of the ice sheets where ice is lost through melting, evaporation, calving and other processes – where it is already warmest on the ice sheet.

At the press conference, Andrew Sheperd presented research carried out by Amber Leeson, on how the location on the ice at which the supraglacial (meaning they form on the surface of the ice) lakes form might change with a warming climate and what this means for the Greenland Ice Sheet.

As the climate warms, higher altitude regions on the ice sheet will too. Through building a hydrological model, Leeson found that the lakes spread father inland. According to Leeson’s simulation

“by 2050, the lakes have spread about 50 to 100 km further inland, so more of the ice sheet is potentially exposed to this lubrication effect,” added Shepard.

This is equivalent to an estimated 48–53% increase in the area over which they are distributed across the ice sheet as a whole.

Previous studies of how the ice sheet might respond to a warming climate do not consider the effects of the added melt water volume at the base of the ice sheet as a result of more lakes at the surface. Leeson’s findings mean that these models need to be re-run so that scientists can fully understand the potential implications. This is particularly true in terms of the lubrication effect at the base of the ice and whether the ice will more readily slip towards the oceans, potentially heightening the risk of sea level rise.

 By Laura Roberts, EGU Communications Officer

 

Further reading and information

You can stream the full press conference by following this link: http://client.cntv.at/egu2015/PC9.

Details of the speakers at the press conference are available at: http://media.egu.eu/press-conferences-2015/#greenland

This blog post presents only some of the findings which were discussed during the press conference. Other aspects of this press conference where covered in the media, you can find more on those here and by following this link.

Kristof Van Tricht, Gorodetskaya, I.V., L’Ecuyer, T. et al. Clouds enhance Greenland ice sheet mass loss, Geophysical Research Abstracts Vol. 17, EGU2015-12737-1, 2015 (conference abstract).

Amber A. Leeson, Sheperd, A., Briggs, K. et al. Supraglacial lakes on the Greenland ice sheet advance inland under warming climate, Nature Climate Change, 5, 51–55, doi:10.1038/nclimate2463, 2015.

Amber A. Leeson, Sheperd, A., Briggs, K. et al. Supraglacial lakes advance inland on the Greenland ice sheet under warming climate, Geophysical Research Abstracts, Vol. 17, EGU2015-934-1, 2015 (conference abstract).

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