Drought-induced depletion of groundwater is no longer an issue that’s out of sight, out of mind.
Research by scientists from Scripps Institution of Oceanography, published this week in Science, describes a GPS technique used to measure drought-induced uplift of land in the western United States. The uplift measurements were used, in turn, to calculate the deficit in surface and near-surface water for the area, which they estimated for March 2014 to be 240 billion tons. That’s equivalent to a 4-inch-thick layer (10 centimeters) of water over the region, or the current annual mass loss from the Greenland Ice Sheet.
GPS is not the only way to measure land displacement caused by the loss of ground and surface water. Scientists have long used the Gravity Recovery and Climate Experiment (GRACE) satellites to estimate groundwater depletion around the planet, as noted by Marcia McNutt in a related editorial.
GRACE’s achievements even graced the cover of the same issue of Science (pictured above). The image shows California’s loss of fresh water (red) from 2002 through 2014. Drought has drained the region of more than 3.6 cubic miles (15 cubic kilometers) of fresh water in each of the past three years.
The image was updated from a version that initially appeared alongside research in 2013 by James Famiglietti of NASA’s Jet Propulsion Laboratory and University of California, Irvine, and Matthew Rodell of NASA’s Goddard Space Flight Center.
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 fielddispatches 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.
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 company—and 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.
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.
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.
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.
Scientists involved in the Minute 319 “pulse flow” say the effort has achieved its main objective: delivering water to special ecological restoration zones along the Colorado River. While cottonwood and willows have retreated from most areas due to a lack of water, conservation groups including the Sonoran Institute and Pronatura Noroeste have been working to revive ecosystems in areas where there is good soil and perhaps enough groundwater and farm runoff to support forests.
At the Laguna Cori, Laguna Grande, and CILA sites, for instance, the Sonoran Institute has been planting saplings, removing invasive plants, and grooming the landscape to make it more likely for trees to germinate. On April 16, 2014, the Operational Land Imager (OLI) on Landsat 8 observed water from the pulse flow replenishing wetlands in these area with water. For comparison, the lower image was acquired on March 31, 2014. The aerial image at the top of the page, first published by the Sonoran Institute, shows the Laguna Granda ecological zone inundated with water on April 14, 2014.
April 16, 2014
March 31, 2014
While greening is not yet visible to Landsat 8, the effects of the pulse flow are visible at ground level. On April 29, the Sonoran Institute began tweeting some of the first images of tree seeds germinating in response to the flow.
The Earth Observing-1 (EO-1) satellite was orbiting at an altitude of about 700 kilometers (400 miles) when it captured our April 11 Image of the Day— a nadir view of Kilauea’s Kahaualeʻa 2 lava flow creeping through forests northeast of Pu’u ’O’o crater. Much closer to the surface, the U.S. Geological Survey monitors the lava flow with helicopter overflights.
The image below shows a portion of the flow as it appeared on March 7, 2014. The smoke near the flow front is caused by lava burning trees and other vegetation in ohia lehua forests. Gases emanating from the vent are visible on the upper left.
(Credit: US Geological Survey/Hawaiian Volcano Observatory)
For more aerial imagery of Kahaualeʻa 2, visit the Hawaiian Volcano Observatory’s multimedia page. The image below was acquired by satellite on March 11, 2014. Click on it for more details.
For the second year in a row, an image from the Canary Islands took the championship of Tournament: Earth. In 2013, a submarine volcano near El Hierro Island was the crowd favorite. This year, it was a shot of the entire island chain that dominated the vote. When “Trailing the Canaries” faced “Activity at Kliuchevskoi” in the championship round, it wasn’t just a win for the Canaries image; it was a blowout. Of the nearly 50,000 votes cast, 96 percent went to the Canary Islands image.
To salute our many readers from the Canaries, we’ve combed through our archives and selected five of our all-time favorite images involving the island chain. They are posted below from oldest to newest. Click on each image for more details. Enjoy!
Dust over the Canary Islands (March 2009)
Teide Volcano (July 2009)
Sand and Tourism in Gran Canaria(January 2013)
El Hierro Submarine Volcano Eruption (2013 Tournament Earth Champion)
Trailing the Canaries (2014 Tournament Earth Champion)
I thought the March Puzzler would be an easy one, but it turned out to be one of the more difficult we’ve posted. As explained in our March 29, 2014, Image of the Day, the image shows Nalabana Bird Sanctuary in India’s Chilika Lake. Despite more than 50 guesses on Earth Matters and 500 on Facebook, nobody came up with the exact location. However, many readers (including Steve Martin and Wendy Spiteri) did recognize the shrimp farms or that it was somewhere in India.
I kept the caption to a few paragraphs, but there’s a lot more that could be written about Chilika Lake. It’s a beautiful and fascinating place that faces environmental, economic, and political challenges that are as complicated as anywhere in the world. In 2002, for instance, authorities dredged a new connection with the Bay of Bengal after silt narrowed the existing mouth and made it more difficult for salty water to enter the lake. While the new mouth increased salinity levels, it did little to resolve the pitched debate between shrimp farmers and traditional fishing communities that has simmered for years. In 1996, the Supreme Court of India banned aquaculture within 1,000 meters (3,300 feet) of Chilika Lake because of environmental concerns, yet enclosures known as “gheries” (which are even visible to satellites…see page 50 of this Powerpoint) remain widespread. You can read more about the ongoing debate about aquaculture in Chilika Lake from Infochange,Economic Times,Radio Netherlands, and the Times of India.