Glacier-calving in Lakes Versus the Sea

August 22nd, 2014 by Adam Voiland

Tidewater glaciers—glaciers that flow from inland mountains all the way into the sea—are perhaps best known for birthing new icebergs in spectacular fashion. As members of James Balog’s Extreme Ice Survey team captured in this clip (above) of Ilulissat Glacier in western Greenland, calving events can feature huge chunks of ice tumbling into roiling waters and be accompanied by loud booming and splashing sounds.

However, tidewater glaciers aren’t the only type of glacier that calve. The ends of lacustrine, or lake, glaciers also break off periodically. Such glaciers gouge depressions in the ground, and those holes fill with melt water to become proglacial lakes. While many of these lakes are small and ephemeral, some are large enough to serve as the backdrop for sizable calving events.

University of Alaska glaciologist Martin Truffer captured this sequence of images (below), which show a calving event at Yakutat Glacier in southeastern Alaska on July 16, 2009. “What we see in the video is a huge iceberg breaking off and rotating. I don’t have a good estimate of the size, but the part of the front that broke of is at least one kilometer long. I think it is quite unusual to see such large ice bergs overturning in lake-calving glaciers. Mostly, they just break off and quietly drift away,” Truffer noted in an email.

There are some key differences between calving events at tidewater and lacustrine glaciers. Tidewater glaciers tend to have much steeper calving fronts than their freshwater cousins. Also, lake water is generally much cooler than seawater, and there is less water circulation in lakes due to the absence of tides. As a result, tidewater glaciers calve much more frequently and are much less likely to have floating tongues of ice, which are common on lake-calving glaciers.

To learn more about Yakutat Glacier, read the Image of the Day we published on August 20, 2014. To learn more about the differences between lake-calving and tidewater glaciers, read this study published in the Journal of Glaciology.  And to see more photographs of Yakutat Glacier, check out Martin Truffer’s field dispatches on his Glacier Adventures blog. I’ve included one of my favorites—an aerial shot taken on September 26, 2011, after Yakut retreated enough that its single calving face had divided into two separate branches. The photograph was taken by William Dryer, one of Truffer’s colleagues.
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Fish Stories from the ISS

August 19th, 2014 by Mike Carlowicz

Since he rocketed to the International Space Station (ISS) on May 29, 2014, American astronaut Reid Wiseman has been enjoying the sights. He has built an active following on Twitter by sharing photographs of a world he is seeing from space for the first time. Like many first-timers in space, he is also discovering some curiosities that most of us never see from the ground.

On August 18, he tweeted the following photo and comment: “Bangkok is the bright city. The green lights outside the city? No idea…”

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Astute Twitter followers, journalists, and bloggers quickly pointed out that @astro_reid was most likely seeing fishing boats, which use bright lamps to draw plankton, squid, and fish to the surface. Several people even pointed to the Earth Observatory and our story about mysterious night lights off the coast of South America. It turns out that Wiseman’s fisherman also appear in the first three seconds of this time-lapse video shot from the ISS as it flew over eastern Asia in January 2014.

A few weeks ago, Wiseman had a similar experience looking out over Taiwan and the coast of China. “Could all those white lights off the coast of Taiwan be fishing boats? Hard to believe.”

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Maybe Wiseman will spot some other strange lights, such as the mystery lights of the Australian Outback…the natural gas flares of the Dakotas…the contrail of a rocket…or gamma-ray rich lightning. The natural sights of the planet at night are far more compelling that any UFO stories.

More Melt Ponds

August 1st, 2014 by Adam Voiland

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We published a photograph of a lone turquoise melt pond as our Image of the Day on August 2, 2014. Although that was one of the largest that scientists participating in the 2014 MABEL campaign saw, it certainly wasn’t the only one. In fact, that melt pond had plenty of companyand we had no shortage of photos of them.

The digital camera that captured the lone melt pond was taking a picture every 3 seconds, with each frame showing an area about 2.5 by 1.5 kilometers (1.6 by 0.9 miles). There were thousands of photographs to choose from, and many of them were spectacular. Above are two favorites. The upper image shows several narrow melt ponds and surface streams on a glacier in southeastern Alaska; the lower photo shows even more melt ponds on thinning sea ice.

Though melt ponds make for nice aerial photographs, they’re also a topic of great interest to scientists. In 2012, American researchers published an interesting study that detailed how melt ponds produce fractal patterns that can be useful for understanding the dynamics of sea ice melting. (For a more readable write-up, try this Scientific American blog post.) In 2014, scientists from the United Kingdom argued that the amount of water in spring melt ponds could be used to make skillful predictions about how much ice will melt during the height of summer.

A View to Remember

August 1st, 2014 by Adam Voiland

Over four missions, astronaut Carl Walz logged 231 days in space. Before the launch of the International Space Station resupply Orb-2 mission  from Wallops Island, Virginia, in July 2014, he described a few of views of Earth from space that he remembers best. Walz is now Vice President of Human Space Flight Operations at Orbital, a Virginia-based aerospace company.

“There was one rare, clear night that sticks out in my memory when I could see all the city lights along the Eastern Seaboard. I’ll never forget those lights. I could see New York, Philadelphia, Washington, all the way west to Chicago all at once. It was just all there…

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…and there was absolutely nothing like flying over Las Vegas at night. You can actually see the colors of the lights. Most city lights are a kind of white light that’s a bit diffuse. Then there’s Las Vegas. It’s this bright spot out in the middle of the desert just staring you in the face…

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…And the storms. We didn’t see any hurricanes because we were flying in the winter and springtime in the Northern Hemisphere, but we did see our share of thunderstorms. Remember, you’re looking at the thunderstorms from the top down. You can’t see lightning directly, but you can see these incredible flashes illuminating the clouds…

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…Oh, of course, we’d sometimes see shooting stars. From that perspective, it was simply jaw-dropping.”

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Editor’s Note: The photographs used to illustrate this post were not taken by Walz.  Click on each of image to find out more about when it was taken. To see more astronaut photographs, check the Earth Observatory Image of the Day on Mondays, browse the archive of astronaut photographs on Visible Earth, or search the Gateway to Astronaut Photography website.

July Puzzler

July 21st, 2014 by Adam Voiland

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Every month on Earth Matters, we offer a puzzling satellite image. The July 2014 puzzler is above. Your challenge is to use the comments section to tell us what part of the world we are looking at, when the image was acquired, what the image shows, and why the scene is interesting.

How to answer. Your answer can be a few words or several paragraphs. (Try to keep it shorter than 200 words). You might simply tell us what part of the world an image shows. Or you can dig deeper and explain what satellite and instrument produced the image, what spectral bands were used to create it, or what is compelling about some obscure speck in the far corner of an image. If you think something is interesting or noteworthy, tell us about it.

The prize. We can’t offer prize money, but, we can promise you credit and glory (well, maybe just credit). Roughly one week after a puzzler image appears on this blog, we will post an annotated and captioned version as our Image of the Day. In the credits, we’ll acknowledge the person who was first to correctly ID the image. We’ll also recognize people who offer the most interesting tidbits of information about the geological, meteorological, or human processes that have played a role in molding the landscape. Please include your preferred name or alias with your comment. If you work for or attend an institution that you want us to recognize, please mention that as well.

Recent winners. If you’ve won the puzzler in the last few months or work in geospatial imaging, please sit on your hands for at least a  day to give others a chance to play.

Releasing Comments. Savvy readers have solved some of our puzzlers after only a few minutes or hours. To give more people a chance to play, we may wait between 24-48 hours before posting the answers we receive in the comment thread.

June Puzzler Answer: Salar de Arizaro

July 3rd, 2014 by Adam Voiland

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Congratulations to Joe Clark for being the first to solve our June puzzler. The answer was the Salar de Arizaro in Argentina’s Salta province. Though once bathed in water, the landscape is now bone dry due to evaporation, baking sunlight, and fierce winds. Read more about it in the image of the day we published on June 28, 2014.  Also, check out this spectacular shot of the Cono de Arita  (a distinctive conical hill sculpted from sandstone) from Ben Stubbs.

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June Puzzler

June 23rd, 2014 by Mike Carlowicz

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Every month on Earth Matters, we offer a puzzling satellite image. The June 2014 puzzler is above. Your challenge is to use the comments section to tell us what part of the world we are looking at, when the image was acquired, what the image shows, and why the scene is interesting.

How to answer. Your answer can be a few words or several paragraphs. (Try to keep it shorter than 200 words). You might simply tell us what part of the world an image shows. Or you can dig deeper and explain what satellite and instrument produced the image, what spectral bands were used to create it, or what is compelling about some obscure speck in the far corner of an image. If you think something is interesting or noteworthy, tell us about it.

The prize. We can’t offer prize money, but, we can promise you credit and glory (well, maybe just credit). Roughly one week after a puzzler image appears on this blog, we will post an annotated and captioned version as our Image of the Day. In the credits, we’ll acknowledge the person who was first to correctly ID the image. We’ll also recognize people who offer the most interesting tidbits of information about the geological, meteorological, or human processes that have played a role in molding the landscape. Please include your preferred name or alias with your comment. If you work for or attend an institution that you want us to recognize, please mention that as well.

Recent winners. If you’ve won the puzzler in the last few months or work in geospatial imaging, please sit on your hands for at least a  day to give others a chance to play.

Releasing Comments. Savvy readers have solved many of our puzzlers after only a few minutes or hours. To give more people a chance to play, we may wait between 24-48 hours before posting the answers we receive in the comment thread.

Earth Science In the News

June 17th, 2014 by Patrick Lynch
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The magnitude of fluorescence portrayed in this visualization prompted researchers to take a closer look at the productivity of the U.S. Corn Belt. The glow represents fluorescence measured from land plants in early July, over a period from 2007 to 2011.

Editor’s Note: This is an excerpt from the NASA Science in the News column published in the May/June issue of the Earth Observer. You can download the current issue of the newsletter here.

Under the Summer Sun, the Corn Belt Is the Most Biologically Productive Place on Earth, Smithsonian Magazine. Rainforests, whether in the Amazon, Southeast Asia, or Central America, are hotspots of organic productivity. Fueled by abundant rain and a reliable stream of nutrients, the Amazon blooms year-round. For a brief period each summer, however, the ingenuity of humankind trumps even the mighty rainforests at biological production. A group of researchers, including Christian Frankenberg and Joanna Joiner have determined that during peak growing season, the Midwest U.S. Corn Belt is the most productive land on Earth. In other words, there’s more photosynthesis going on here than in the Amazon. When plant cells photosynthesize, part of the energy they produce is emitted as fluorescent light. By measuring the strength of this fluorescence from space, scientists can get a measure of plant productivity.

Arctic Melting Is Lasting Longer and Affecting More Ice, UniverseToday.com. The Arctic melt season is averaging five days longer with each passing decade, a new study by NASA and the National Snow and Ice Data Center reveals. More ice-free days mean the water (which is darker than the surrounding ice) is exposed longer and can absorb more of the Sun’s heat, further increasing the melting rate and extent. The study shows that thickness of the Arctic ice cap has shrunk by as much as 1.2 meters (4 feet). By the end of this century, scientists believe the Arctic Ocean will be ice-free during the entire summer. This news came in the same week that the Intergovernmental Panel on Climate Change released its own report on global warming. Data were collected with NASA’s (long-deceased) Nimbus-7 Scanning Multichannel Microwave Radiometer and instruments onboard Defense Meteorological Satellite Program spacecraft. Scientists can measure the changes in the ice’s microwave emissivity using a formula developed by co-author Thorsten Markus.

NASA Study Projects Higher Temperatures Despite Recent Slowdown in Global Warming, Bloomberg. Despite a recent slowdown in the rate of global warming, a study by Drew Shindell suggests global temperatures will likely continue to rise in coming decades, on track with earlier estimates of increasing temperatures. Shindell and his colleagues sought to reconcile different estimates for the Earth’s climate sensitivity, or how temperatures change in response to changes in radiative forcing. Some studies estimate low climate sensitivity, based on the assumption that global average temperatures would respond uniformly to increases of carbon dioxide (CO2) and other greenhouse gas emissions. But the NASA study showed that global temperatures are more sensitive to changes in aerosols and ozone in the atmosphere than was thought. This higher sensitivity could mean a larger and faster temperature response. Shindell said the study’s findings could have “a really profound impact” on the amount of greenhouse gas emission reductions needed for countries to meet an international goal of limiting temperature increases to 2°C (3.6 °F). “I wish it weren’t so,” said Shindell, “but forewarned is fore-armed.” Global temperatures have increased at a rate of 0.12 °C (0.22 °F) per decade since 1951, according to the NASA GISS temperature record. This trend has been interrupted since 1998, as since then the rate of warming has slowed to only 0.05 °C (0.09 °F) per decade—even as atmospheric CO2 continues to rise.

Amazon Rainforest Breathes In More Than It Breathes Out, LiveScience.com. A new study further confirms that pristine Amazon forests pull in more CO2 than they put back into the atmosphere, helping to reduce global warming by lowering the planet’s greenhouse gas levels. When scientists account for the world’s CO2, their totals suggest some of the greenhouse gas disappears into land-based carbon traps. These natural carbon sinks, such as forests, absorb and store CO2, helping to lower the greenhouse gas levels in the atmosphere. To better measure the carbon flux from the Amazon, researchers tracked tree death throughout the Amazon. Lead study author Fernando Espírito-Santo combined satellite data, airborne lidar data (i.e., laser surface imagery), and tree counts to compare carbon consumed by living trees with emissions from dead trees. Espírito-Santo found that dead Amazonian trees emit an estimated 1.9 billion tons (1.7 billion metric tons) of carbon to the atmosphere each year. In a normal year, the Amazon rainforest absorbs about 2.2 billion tons (2 billion metric tons) of CO2, studies suggest. The study also found that big storms that can blow down millions of trees at once barely budge the forest’s carbon output.

May Puzzler Answer: Manning Islands

May 27th, 2014 by Adam Voiland

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We do have a few Trekkies on staff, but we didn’t actually have a Star Trek communicator in mind when we selected the May Puzzler. Nor were we trying to puzzle you by showing something from under a microscope. However, we did intend for the May puzzler to be tough because last month it was solved in a matter of minutes.

With that in mind, we choose an area that looks quite different on Google Maps than it does to NASA satellites. If you look carefully, you’ll notice that Google Maps imagery can be spotty in some areas, particularly in the high latitudes and over the oceans. For instance, compare how Nunavut’s Manning Islandsthe answer to the puzzlerlook on Google Maps (below) compared to the Advanced Land Imager (ALI) on July 26, 2012 (above).

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Despite the hundreds of answers we received, nobody noticed that the Manning Islands were hidden away amidst all the sea ice. However, a few readers came close. On Facebook, Owen Anfinson hypothesized that the image showed pack ice in the Arctic during the summer, even pointing out that it was most likely sea ice near land because of all the sediment-covered ice.  Meanwhile, Laura Yeo guessed that the image showed “rapid ice melt in the Northwest Passage in the summer of 2012.”  Nice work, Owen and Laura.  For more more details about the Manning Islands, read the Image of the Day we published on May 23, 2014.

For some background about the satellite imagery on Google Earth, try this post from the Google Earth Blog. For more details about ALI, see the feature story we published in 2010. As a bonus for blog readers, you’ll find a broader view of Foxe Basin as seen by the Moderate Resolution Imaging Spectroradiometer (MODIS) on August 1, 2002, below.

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Colorado River Reaches the Sea of Cortez

May 22nd, 2014 by Adam Voiland

 

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When the Minute 319 “pulse flow” began in March 2014, it was not clear whether the effort would be enough to reconnect the Colorado River with the Sea of Cortez. Some hydrologists thought there might be just enough water; others were less optimistic. It turns out the optimists were right, though just barely. For the first time in sixteen years, the Colorado River was reunited with the Sea of Cortez on May 15, 2014.

While scientists involved in the effort point out the goal was always to recharge groundwater and deliver water to special ecological restoration zones, environmental advocates haven’t been shy about basking in the symbolic importance of the river reaching the sea. “Now that we’ve witnessed the Colorado flowing in its delta, we know that it is possible to conjure the river back to life where the world thought it was dead.  It’s a resurrection that we won’t soon forget, and a vision of what could be in the future,” wrote Jennifer Pitt, the director of the Environmental Defense Fund’s Colorado River Project in an article published by National Geographic

Francisco Zamora, director of the Sonoran Institute’s Colorado River Delta Legacy Program, took these photograph from a Lighthawk-supported plane on May 15, 2014. See the Sonoran Institute’s Facebook page for more images. To learn more about the scientific rational behind the pulse flow, see this EOS article. View satellite imagery of the pulse flow here.

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