A series of research papers in recent months shows that we know more than ever before about the ice on our land and covering the seas. In case you missed them, here’s a look at some of the notable findings. Many are based on data from NASA’s ICESat-2 satellite, which just over a year ago released to the public more than a trillion new measurements of Earth’s height. With these and other satellite data scientists have …
… Produced the First Satellite-Based Maps of Snow Depth on Sea Ice
Earlier this month we wrote about how the data were used to make the first maps of snow depth on sea ice. The research, published in JGR Oceans, shows how elevation measurements from ICESat-2 can be combined with data from ESA’s Cryosat-2 to get maps like these:
The snow layer is an important component of the sea ice system, affecting how the ice cover grows and melts. With additional years of observations, such maps could help scientists assess how climate change affects precipitation and the accumulation of snow.
… Estimated the Thinning of Arctic Sea Ice
In another paper, scientists described how they used ICESat-2 data and a new model to estimate the thickness of Arctic sea ice. Comparing the new estimates to those made with the first ICESat mission (2003-2009), they found that sea ice in winter has thinned by as much as 20 percent in the past 11 years. The bottom-left map shows the February-March 2019 thickness estimate; the bottom-right map shows how much thickness has changed between 2008 and 2019. Read more about that study here.
… Measured Ice Sheet Losses Spanning 16 Years
Other research outlined the changes happening to ice on land. In a paper published April 2020 in Science, scientists chronicled 16-years of change to the Greenland and Antarctic ice sheets.
ICESat-2 data from 2019 showed that Greenland’s ice sheet had lost an average of 200 million metric tons of ice per year since the original ICESat started collecting data in 2003. Antarctica’s ice sheet lost an average of 118 million metric tons of ice per year during the same period.
But the beauty of the new measurements from ICESat-2 is that scientists can show details of where the changes are happening. Not only can they discern where the ice sheets have been thinning or thickening, but they can see changes on the scales of individual glaciers and, for the first time, across floating ice shelves. Read this story for more details, or check out the video below.
… Detailed the Retreat of a Potentially Unstable Glacier in East Antarctica
The ice in East Antarctica is generally thought to be less vulnerable than the ice in West Antarctica and the Antarctic Peninsula. Research in 2018, however, pointed to a number of glaciers along East Antarctica’s coastline that appear to be destabilizing. A new paper published March 2020 detailed the changes happening to Denman Glacier. The stability of Denman is a concern because this one glacier in East Antarctica holds as much ice as half of West Antarctica.
Scientists used satellite radar data from the Italian COSMO‐SkyMed constellation to detect the retreat of the glacier’s grounding line—the point at which a glacier last touches the seafloor and begins to float. If the grounding line continues to retreat, warm seawater could eventually penetrate upstream and beneath the glacier, continuing to melt it from below and destabilizing it. Read the full story here.
… Observed a Sixfold Increase in Ice Loss from Antarctica & Greenland Since the 1990s
Sometimes multiple satellites can tell you more than a single satellite. In research published in Nature, scientists used observations from 11 satellite missions to calculate losses from the Antarctic and Greenland ice sheets since the 1990s. They show that the ice sheets together lost 81 billion metric tons per year in the 1990s, compared with 475 billion metric tons of ice per year in the 2010s—a sixfold increase.
The meltwater associated with the ice loss boosted global sea levels by 17.8 millimeters (0.7 inches), according to a story about the research.
… Calculated Ice Melt Leading to Regional Freshwater Depletion
Some losses are directly affecting the freshwater resources available to people. In the 20thcentury, the largest contributors to sea level rise came from melting ice caps and glaciers in Alaska, the Canadian Arctic Archipelago, the Southern Andes, High Mountain Asia, the Russian Arctic, Iceland, and Svalbard.
Researchers used the GRACE and GRACE-FO satellites to determine that these seven regions lost (on average) more than 280 billion metric tons of ice per year between 2002 and 2019. The losses contributed 13 millimeters (0.5 inches) to global sea level rise. The losses also deplete a freshwater resource for communities that depend on the ice to provide meltwater for agriculture and drinking water. You can read more about the research, published April 2020 in GRL, in this story.
Ever since a new and deadly strain of coronavirus (SARS-CoV-2) emerged in China and then spread around the world, the virus has upended life in many countries. Scientists at NASA and other institutions have hustled to track and make sense of our new reality with every tool and technique at their disposal, including satellite data.
As several comprehensive NASA-funded research projects get started, here is a quick roundup of some of the more interesting satellite-related findings about the science of coronavirus and its effects on the environment.
A Welcome Breath of Cleaner Air
Much of the news about the new coronavirus is grim, but observations of air quality offer a breath of fresh air. Several satellite sensors have detected drops in air pollutants — including nitrogen dioxide, carbon monoxide, and fine particles — following restrictions on travel and economic activity. Teams of scientists have spotted changes in China, Europe, the U.S. Northeast and Southeast, and India.
Look here for some tips on how to find and visualize changes in nitrogen dioxide, one of the gases that most clearly shows the effects of quarantines and economic shutdowns. Also, look here for nitrogen dioxide data for cities all around the world. But beware: As University of Georgia meteorologist Marshall Shepherd has pointed out, clouds and rain can create confusing changes in nitrogen dioxide that have nothing to do coronavirus restrictions.
A New Coronavirus Tracking Tool
Given how much the virus has changed daily life, many of us find ourselves turning into armchair epidemiologists, trying to make sense of how the virus is spreading and what it means for our local area. If you are interested in taking a close look at new data as it comes in, this simple-to-use mapping tool from NASA’s Socioeconomic Data and Applications Center (SEDAC) might be of interest. It features demographic data, along with regularly updated information on reported global cases of the novel coronavirus (COVID-19). There is a short user guide here.
A Stream of New Seasonality Studies
One of the key unknowns about the new coronavirus is whether environmental conditions — such as temperature, humidity, and exposure to ultraviolet light — have any effect on how the virus spreads or on the severity of the symptoms. NASA-funded researchers are starting to investigate this in several ways, while others are using NASA data in their models and analyses.
Billions of people are facing something that NASA astronauts have plenty of experience with—living in social isolation for long periods with just a few other people. Here are some tips from astronaut Anne McClain and psychologist Tom Williams.
If you follow science news, this will probably sound familiar.
In May 2019, when atmospheric carbon dioxide reached its yearly peak, it set a record. The May average concentration of the greenhouse gas was 414.7 parts per million (ppm), as observed at NOAA’s Mauna Loa Atmospheric Baseline Observatory in Hawaii. That was the highest seasonal peak in 61 years, and the seventh consecutive year with a steep increase, according to NOAA and the Scripps Institution of Oceanography.
The Mauna Loa Observatory has been measuring carbon dioxide since 1958. The remote location (high on a volcano) and scarce vegetation make it a good place to monitor carbon dioxide because it does not have much interference from local sources of the gas. (There are occasional volcanic emissions, but scientists can easily monitor and filter them out.) Mauna Loa is part of a globally distributed network of air sampling sites that measure how much carbon dioxide is in the atmosphere.
The broad consensus among climate scientists is that increasing concentrations of carbon dioxide in the atmosphere are causing temperatures to warm, sea levels to rise, oceans to grow more acidic, and rainstorms, droughts, floods and fires to become more severe. Here are six less widely known but interesting things to know about carbon dioxide.
The rate of increase is accelerating.
For decades, carbon dioxide concentrations have been increasing every year. In the 1960s, Mauna Loa saw annual increases around 0.8 ppm per year. By the 1980s and 1990s, the growth rate was up to 1.5 ppm year. Now it is above 2 ppm per year. There is “abundant and conclusive evidence” that the acceleration is caused by increased emissions, according to Pieter Tans, senior scientist with NOAA’s Global Monitoring Division.
Scientists have detailed records of atmospheric carbon dioxide that go back 800,000 years.
To understand carbon dioxide variations prior to 1958, scientists rely on ice cores. Researchers have drilled deep into icepack in Antarctica and Greenland and taken samples of ice that are thousands of years old. That old ice contains trapped air bubbles that make it possible for scientists to reconstruct past carbon dioxide levels. The video below, produced by NOAA, illustrates this data set in beautiful detail. Notice how the variations and seasonal “noise” in the observations at short time scales fade away as you look at longer time scales.
CO2 is not evenly distributed.
Satellite observations show carbon dioxide in the air can be somewhat patchy, with high concentrations in some places and lower concentrations in others. For instance, the map below shows carbon dioxide levels for May 2013 in the mid-troposphere, the part of the atmosphere where most weather occurs. At the time there was more carbon dioxide in the northern hemisphere because crops, grasses, and trees hadn’t greened up yet and absorbed some of the gas. The transport and distribution of CO2 throughout the atmosphere is controlled by the jet stream, large weather systems, and other large-scale atmospheric circulations. This patchiness has raised interesting questions about how carbon dioxide is transported from one part of the atmosphere to another—both horizontally and vertically.
Despite the patchiness, there is still lots of mixing.
In this animation from NASA’s Scientific Visualization Studio, big plumes of carbon dioxide stream from cities in North America, Asia, and Europe. They also rise from areas with active crop fires or wildfires. Yet these plumes quickly get mixed as they rise and encounter high-altitude winds. In the visualization, reds and yellows show regions of higher than average CO2, while blues show regions lower than average. The pulsing of the data is caused by the day/night cycle of plant photosynthesis at the ground. This view highlights carbon dioxide emissions from crop fires in South America and Africa. The carbon dioxide can be transported over long distances, but notice how mountains can block the flow of the gas.
Carbon dioxide peaks during the Northern Hemisphere spring.
You’ll notice that there is a distinct sawtooth pattern in charts that show how carbon dioxide is changing over time. There are peaks and dips in carbon dioxide caused by seasonal changes in vegetation. Plants, trees, and crops absorb carbon dioxide, so seasons with more vegetation have lower levels of the gas. Carbon dioxide concentrations typically peak in April and May because decomposing leaves in forests in the Northern Hemisphere (particularly Canada and Russia) have been adding carbon dioxide to the air all winter, while new leaves have not yet sprouted and absorbed much of the gas. In the chart and maps below, the ebb and flow of the carbon cycle is visible by comparing the monthly changes in carbon dioxide with the globe’s net primary productivity, a measure of how much carbon dioxide vegetation consume during photosynthesis minus the amount they release during respiration. Notice that carbon dioxide dips in Northern Hemisphere summer.
It isn’t just about what is happening in the atmosphere.
Most of Earth’s carbon—about 65,500 billion metric tons—is stored in rocks. The rest resides in the ocean, atmosphere, plants, soil, and fossil fuels. Carbon flows between each reservoir in the carbon cycle, which has slow and fast components. Any change in the cycle that shifts carbon out of one reservoir puts more carbon into other reservoirs. Any changes that put more carbon gases into the atmosphere result in warmer air temperatures. That’s why burning fossil fuels or wildfires are not the only factors determining what happens with atmospheric carbon dioxide. Things like the activity of phytoplankton, the health of the world’s forests, and the ways we change the landscapes through farming or building can play critical roles as well. Read more about the carbon cycle here.
Seven million years ago, some truly spectacular creatures roamed the woodlands of East Africa. There was a moose-like giraffe called Shiva’s beast. There were giant buffalo with horns wider than the animals were tall. And the lumbering creatures known as anthracotheres defy easy categorization.
“Whenever I ask colleagues who study anthracotheres how they describe them, they always say: hippo-pig,” laughed Tyler Faith, curator of archaeology at the Natural History Museum of Utah. As for the buffalo: “This was a horn span of 3 meters (10 feet). I mean this was an awesome buffalo.”
These and several dozen variations of more recognizable African megaherbivores — elephants, rhinos, hippos, and giraffes — all went extinct within the past several million years. For decades, archaeologists have pinned the blame on early humans, particularly Homo erectus, a species that emerged 2 million years ago, walked upright, and had a body plan similar to modern humans. Since Homo erectus made stone weapons and was capable of butchering large game, many archaeologists assumed that it hunted Africa’s megaherbivores into extinction — much like the fossil record suggests Homo sapiens (modern humans) did to the large mammals of North and South America some 11,000 years ago.
But nobody rigorously tested whether this “overkill hypothesis” fit with the fossil record. “Speculation had been repeated often enough that it just graduated into fact; it became the truth,” Tyler explained during a recent colloquium at NASA’s Goddard Space Flight Center. To check more rigorously, Tyler and colleagues analyzed fossil assemblages from 101 sites in Eastern Africa.
What they found was a surprise. Megaherbivores began disappearing about 4.6 million years ago — long before Homo erectus came on the scene (1.8 million years ago). And there was no increase in the rate of extinctions even when Homo erectus and butchering showed up in fossil records.
However, when the researchers looked at some key indicators of past environmental conditions, they found one key change — the expansion of grasslands — lined up with the extinctions almost perfectly. Five million years ago, classic open grasslands like today’s Serengeti Plain did not exist in East Africa. Trees and shrubs were a much more dominant part of that African landscape then, explained Tyler.
But as carbon dioxide levels declined, mainly due to orbital variations and changes in the amount of Earth covered by ice, forests retreated and grasslands became dominant. Since many of the megaherbivores fed mainly on woody vegetation, they likely faded away along with their food sources. Meanwhile, other familiar species thrived. The ancestors of wildebeest, hartebeests, Thompson gazelles, oryx, plains zebras, and warthogs — all grazers that live in open habitats — proliferated.
Faith’s bottom line is that it is time to stop blaming Homo erectus for something they didn’t do. “In the search for ancient hominid impacts on ancient African ecosystems, we must focus our attention on the one species known to be capable of causing them – us, Homo sapiens, over the past 300,000 years,” he said.
From afar, Earth’s oceans look quite blue. But closer inspection reveals a much more complex palette. Tiny particles floating in the water (phytoplankton, pollution, and sediments) can change how light is absorbed and scattered, which affects the apparent color of the water near its surface.
Color is useful for scientists who model how the oceans might evolve with time and climate change. “It’s cool to see how all of these global Earth models—completely different when it comes to their complexity—use the color of the ocean to explain the changes in the future,” said Ivona Cetinic, an ocean ecologist at NASA’s Goddard Space Flight Center.
In one example, NASA-funded researchers showed large areas of the planet’s blue water becoming even bluer. The change would come from a decline in green-pigmented phytoplankton as the planet warms. You can read more about that study in Nature Communications, or check out some of the media coverage.
In a different study published in Geophysical Research Letters (GRL), researchers from NASA Goddard found that the “yellowing” of coastal waters could lead to cooler global ocean temperatures. Yellow-brown waters already show up around some coastal areas where rivers meet the ocean—such as the outwash from the Mackenzie River in northern Canada (above). Pulses of water from the spring melt move a huge amount of dissolved organic material and sediment into the Beaufort Sea. Coastal waters could become yellower over time if increases in precipitation and melting on land wash more dissolved organic material out to the ocean.
The researchers ran simulations that incorporated NASA ocean-color data and showed that after 300 years, the top 700 meters of a “yellow” ocean with dissolved organic material and plankton would be colder than a “green” phytoplankton-only ocean. That’s because yellow water lets less light and heat pass through the top layer of water, keeping it cooler below.
The authors wrote in the GRL paper: “We suggest that an increase in these yellowing materials behaves as a buffer that mitigates some effects of a warming climate.”
On February 27, 2014, a Japanese rocket launched NASA’s latest satellite to advance how scientists study raindrops from space. The satellite, the Global Precipitation Measurement (GPM) Core Observatory, paints a picture of global precipitation every 30 minutes, with help from its other international satellite partners. It has provided innumerable insights into Earth’s precipitation patterns, severe storms, and into the rain and snow particles within clouds. It has also helped farmers trying to increase crop yields, and aided researchers predicting the spread of fires.
In honor of GPM’s fifth anniversary, we’re highlighting some of our favorite and most unique Earth Observatory stories, as made possible by measurements taken by GPM.
The Second Wettest
October in Texas Ever
In Fall 2018, storm after storm rolled through and dumped
record rainfall in parts of Texas. When Hurricane Willa hit Texas around
October 24, the ground was already soaked. One particularly potent cold front
in mid-October dropped more than a foot of rain in areas. By the end of the
month, October 2018 was the second wettest month in Texas on record.
GPM measured the total amount of rainfall over the region from October 1 to October 31, 2018. The brightest areas reflect the highest rainfall amounts, with many places receiving 25 to 45 centimeters (10 to 17 inches) or more during this period. The satellite imagery can also be seen from natural-color satellite imagery.
Observing Rivers in
With the GPM mission’s global vantage point, we can more
clearly see how weather systems form and connect with one another. In
this visualization from October 11-22, 2017, note the long, narrow
bands of moisture in the air, known as “atmospheric rivers.” These
streams are fairly common in the Pacific Northwest and frequently bring much of
the region’s heavy rains and snow in the fall and winter. But this atmospheric
river was unusual for its length—extending roughly 8,000 kilometers (5,000
miles) from Japan to Washington. That’s about two to three times the typical
length of an atmospheric river.
Since atmospheric rivers often bring strong winds, they can force moisture up and over mountain ranges and drop a lot of precipitation in the process. In this case, more than four inches of rain fell on the western slopes of the Olympic Mountains and the Cascade Range, while areas to the east of the mountains (in the rain shadow) generally saw less than one inch.
Increasing Crop Yield
for Farmers in Pakistan
Knowing how much precipitation is falling or has fallen is
useful for people around the world. Farmers, in particular, are interested in
knowing precipitation amounts so they can prevent overwatering or underwatering
The Sustainability, Satellites, Water, and Environment (SASWE) research group at the University of Washington has been working with the Pakistan Council of Research in Water Resources (PCRWR) to bring this kind of valuable information directly to the cell phones of farmers. A survey by the PCRWR found that farmers who used the text message alerts reported a 40 percent savings in water. Anecdotally, many farmers say their income has doubled because they got more crops by applying the correct amount of water.
The map above shows the forecast for evapotranspiration for October 16-22, 2018. Evapotranspiration is an indication of the amount of water vapor being removed by sunlight and wind from the soil and from plant leaves. It is calculated from data on temperature, humidity, wind speed, and solar radiation, as well as a global numerical weather model that assimilates NASA satellite data. The team also looks at maps of precipitation, temperature and wind speed to help determine crop conditions. Precipitation data comes from GPM that is combined with ground-based measurements from the Pakistan Meteorological Department.
Precipitation can drastically affect the spread of a fire. For
instance, if a region has not received normal precipitation for weeks or
months, the vegetation might be drier and more prone to catching fire.
NASA researchers recently created a model that analyzes various weather factors that lead to the formation and spread of fires. The Global Fire Weather Database (GFWED) accounts for local winds, temperatures, and humidity, while also being the first fire prediction model to include satellite–based precipitation measurements.
The animation above shows GFWED’s calculated fire danger around the world from 2015 to 2017. The model compiles and analyzes various data sets and produces a rating that indicates how likely and intense fire might become in a particular area. It is the same type of rating that many firefighting agencies use in their day–to–day operations. Historical data are available to understand the weather conditions under which fires have occurred in the past, and near–real–time data are available to gauge current fire danger.
In this mountainous country of Nepal, 60 to 80 percent of the annual precipitation falls during the monsoon (roughly June to August). That’s also when roughly 90 percent of Nepal’s landslide fatalities occur. NASA researchers have designed an automated system to identify potential landslides that might otherwise go undetected and unreported. This information could significantly improve landslide inventories, leading to better risk management.
The computer program works by scanning satellite imagery for signs that a landslide may have occurred recently, looking at topographical features such as hill slopes.
The left and middle images above were acquired by the Landsat 8 satellite on September 15, 2013, and September 18, 2014—before and after the Jure landslide in Nepal on August 2, 2014. The image on the right shows that 2014 Landsat image processed with computer program. The red areas show most of the traits of a landslide, while yellow areas exhibit a few of the proxy traits.
The program also uses data from GPM to help pin when each landslide occurred. The GPM core satellite measures rain and snow several times daily, allowing researchers to create maps of rain accumulation over 24-, 48-, and 72-hour periods for given areas of interest—a product they call Detecting Real-time Increased Precipitation, or DRIP. When a certain amount of rain has fallen in a region, an email can be sent to emergency responders and other interested parties.
The GPM Core
Observatory is a joint satellite project by NASA and the Japan Aerospace
Exploration Agency. The satellite is part of the larger GPM mission, which
consists of about a dozen international satellite partners to provide global
observations of rain and snow.
NASA was mostly shut down for January 2019, but Earth wasn’t. In case you missed it, here are some of the big stories we didn’t cover during the impasse.
Scientists Find Evidence of An Ancient Earth Rock on the Moon Four billion years ago, the Moon was about three times closer to Earth than it is now. So if a large asteroid or comet slammed into Earth and jettisoned material into space, it was more likely that rock fragments might end up landing on the Moon. That’s how an international team of scientists working with the Center for Lunar Science and Exploration (CLSE) think that a small fragment composed of quartz, feldspar, and zircon—a combination of minerals commonly found on Earth—ended up embedded within a larger Moon rock collected by Apollo astronauts. The team recently revealed evidence from the ancient rock fragment, suggesting that it is one of the oldest Earth rocks ever found.
A Rare Typhoon Hits Thailand It is rare for powerful tropical storms to strike Thailand. Before January 2019, the last time it happened was 1962. So meteorologists took notice when Tropical Storm Pabuk slammed into southern Thailand on January 4, 2019, packing sustained winds of 95 kilometers per hour (60 mph) and delivering torrential rains to some of Thailand’s most popular tourist destinations. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this image of the storm on January 4, 2019.
Snow Falls in Algeria (Yes, the Sahara) In another unusual weather event, fresh snow created surreal scenery in Algeria when it coated Saharan desert dunes in mid-January. This is just the third time snow has fallen in Ain Sefra, the gateway to the Sahara Desert, in the past 37 years. (The last time was 2018.) The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured an image of the snow on January 14, 2019. It is composed with false color, using a combination of infraed and visible light (MODIS bands 7-2-1). Snow appears blue with this band combination.
China’s War on Particulates May Be Making Ozone Pollution Worse For the past few years, China has advanced an ambitious plan to reduce emissions of fine particulate (PM2.5), a harmful type of air pollution. Authorities have restricted the number of vehicles on the roads, capped how much coal industries can burn, and shuttered many polluting factories and power plants. The result has been impressive: over five years, concentrations of PM2.5 in eastern China have fallen nearly 40 percent. But, there is another wrinkle. Particulates also sponge up substances that make it harder for ground-level ozone to form. So even as concentrations of PM2.5 decline, ozone concentrations are rising, new research shows.
Can Satellites SensePoverty? Increasingly, yes, at least in rural areas. By analyzing observations of villages in Kenya, one team of researchers recently showed that land use and land cover data from satellites contains some useful clues for identifying the poorest households in rural areas. Key indicators included: the size of buildings within a homestead, the amount of bare agricultural land adjacent to a homestead, and the length of the growing season. The researchers think this type of information could make it easier to monitor the progress of efforts designed to reduce poverty in rural areas, such as the U.N. Sustainable Development Goals.
A meteor exploded over western Cuba on February 1, 2019, and it delivered an impressive light show. The event was captured by numerous ground-based cameras. It was also spotted from space.
Researchers from the Cooperative Institute for Meteorological Satellite Studies wrote a blog post showing a series of images and data from the event, including the animation above. It was composed from false-color images gathered by NOAA’s GOES-16 satellite. (NASA builds GOES satellites for NOAA.) The dark blue pixels moving toward the northeast appear to be the signature of a debris cloud drifting in the atmosphere after the meteor exploded. A close look at visible imagery from GOES-16 reveals a shadow apparently cast by the debris cloud.
Meanwhile, scientists at NASA’s Short-term Prediction Research and Transition Center (SPoRT) reported signs of the meteor flash in an image acquired by the Geostationary Lightning Mapper (GLM). The meteor flash appears in this image as blue pixels over Cuba. (The blue in the top-left corner is lightning activity over the ocean.)
Last year, we published a story explaining how scientists had used satellite images of rocks stained pink with guano to discover several unexpectedly large colonies of Adélie penguins on the Danger Islands. Now the researchers are back with a new announcement: Using Landsat data, they have analyzed how the size of that penguin population has changed since 1982. They also used Landsat’s deep archive of satellite imagery to analyze what the penguins eat and whether their diets have changed over the past three decades.
“While the Adélie population [on the Danger Islands] is massive, it was even larger in the past,” said Heather Lynch of Stony Brook University. “We believe the population peaked in the late 1990s and has been on a slow steady decline ever since.” The scientists are still working out what may have caused the 10 to 15 percent decline in the population, but they think it is probably related to changing environmental conditions.
Adélie penguins are particularly sensitive to changes in climate because they require ice-free land areas to breed and access to open water. They also need enough sea ice to support populations of key food sources. The researchers thought that changing diets would accompany the decline in population, but by analyzing the spectral signatures of all the guano stains found in cloud-free Landsat image of the islands since 1982, they were surprised to discover the penguins’ diets have stayed the same.
Penguin guano ranges from white to pink to dark red. White guano is from eating mostly fish; pink and red is from mostly eating krill. The University of Connecticut’s Casey Youngflesh, however, noticed some intriguing regional patterns in what Adélie penguins eat. Colonies in West Antarctica tend to eat more krill, while colonies in East Antarctic consume more fish. The reasons for the difference are not clear, though Youngflesh is looking into the possibility that differences in the Antarctic silverfish population may be a factor.
Discovering the big colonies on the Danger Islands has also opened up a new pathway for figuring out when penguins first arrived. By digging through layers of guano-stained pebbles during a recent field expedition and dirt and dating them with radiocarbon techniques, Michael Polito of Louisiana State University worked out that penguins must have arrived on the Danger Islands about 2,900 years ago, thousands of years earlier than previous evidence suggested.
Credits: Heather Lynch, Stony Brook University.
Expect to hear even more guano-stained discoveries in the future. “We are only just scratching the surface of what we can do in terms of tracking seabirds from space,” said Lynch. “We should be able to extend the technique to snow petrel, boobies, and cormorants.”
Lynch put the total number of penguins on the Danger Islands at roughly 1.5 million (individual birds) — more than live on all the rest of the Antarctic Peninsula combined.
Read more about the Danger Island Adélie penguins from NASA and MAPPPD.