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Salt lakes in Western Australia
Credits: OLI/Landsat 8/NASA
Credits: OLI/Landsat 8/NASA

Satellite Eye on Earth: March 2016 - in pictures

This article is more than 7 years old

Salt lakes, dust rivers and ice shelves were among the images captured by European Space Agency and Nasa satellites last month

Thousands of saline lakes span the south-western part of Western Australia, at the headwaters of the Frankland river, north of Stirling Range national park.

Millions of years ago, declines in rainfall caused river flows to ebb and river valleys to fill in with sediment. Wind then sculpted the loose sediment to form the lake basins that remain today. Some of the lakes now fill with runoff directly from the Stirling Range; others are controlled primarily by groundwater.

Many of the saltwater lakes in this region are short-lived. Still, a range of salt-loving aquatic invertebrates, such as brine shrimp, have adapted to the tough conditions. They can handle both the temporary absence of water, and water that can be several times saltier than seawater.

Credits: Epic/ DSCOVR/Nasa

The Deep Space Climate Observatory captures a total eclipse of the sun from space for the first time, showing the shadow of the moon marching across Earth’s sunlit face, on 9 March.

How fracking has changed the landscape
Credits: OLI/Landsat 5and Landsat 8/Nasa

In the early 2000s, the area east of Cotulla, Texas, was dry, sleepy shrubland. By 2015, a bustling network of roads and rectangular drill pads had completely transformed the landscape. The pair of satellite images below shows how much the landscape has changed - the “before” image was captured in December 2000; the “after” image in December 2015. According to a report from the Texas Observer, Cotulla saw its population swell from about 4,000 to 10,000 people in just a few years due to an influx of oil and gas workers for “fracking”.

Credits: VIIRS/Suomi NPP/NASA Photograph: VIIRS/Suomi NPP/NASA

In nighttime satellite imagery, the light from the Eagle Ford shale formation competes with the nearby cities of San Antonio and Austin. The electric glow of drilling equipment, worker camps, and other gas and oil infrastructure combine with flickering gas flares to create an unmistakable arc of light across southern Texas.

Photograph: AIRS/Aqua/NASA

The Atmospheric Infrared Sounder aboard Nasa’s Aqua satellite shows global methane concentrations in January 2016 at a pressure of 400 hectopascals, or roughly 6km above the surface.

Methane is a chemical compound that shows up nearly everywhere on the planet. It bubbles up from swamps and rivers, belches from volcanoes, rises from wildfires, and seeps from the guts of cows and termites. Human settlements are awash with the gas. Methane leaks silently from natural gas and oil wells and pipelines, as well as coal mines. It stews in landfills, sewage treatment plants, and rice paddies.

It is one of the most potent greenhouse gases, and yet the reasons for why and where it shows up are often a mystery. What science shows is that a lot more methane has made its way into the atmosphere since the beginning of the industrial revolution. Less understood is why the ebb and flow of this gas has changed in recent decades.

Since 2007, methane has been on the rise, and no one is quite sure why. Some scientists think tropical wetlands have gotten a bit wetter and are releasing more gas. Others point to the natural gas fracking boom in North America and its sometimes leaky infrastructure. Others wonder if changes in agriculture may be playing a role.

Credits: MODIS/Terra/NASA

A river of dust flows from the Saharan desert across the Mediterranean Sea behind a strong cold front. A line of heavy cloud marks the leading edge of the cold front as it marches from east to west. The landscape ahead of the front appears crisply defined while cloud and dust obscure most of the land and water from view behind the leading edge. This cold front was part of a cyclonic system named Golia that created severe weather across the region.

Italy was hit especially hard, with heavy rain, high wind gusts, and storm surges battering the southern part of the country while snowstorms hit the north. Five people were reported killed in Italy from extreme weather caused by Golia.

As the cold front moved across the Mediterranean, sand and dust from as far south as the Sahara desert rode moved behind the front. It is not uncommon for strong southerly winds to carry dust from Africa across the Mediterranean. The dramatic spectacle of a massive movement of Saharan dust behind a crisp cold front is more rarely captured from space.

Credits: VIIRS/Suomi NPP/NASA

A satellite view of the the northern lights (Aurora borealis) on 7 March, which appear as white streaks over Iceland, the north Atlantic and Norway.

It is not often that the northern lights are visible south of Scotland and Northern Ireland, but a geomagnetic storm coloured night skies over a much wider swath of the country.

The brilliant colours of the aurora are provoked by activity the sun: solar energy and particles speed toward Earth in a steady stream called the solar wind, or they rush out in massive eruptions known as coronal mass ejections. These storms disturb geospace (the space around Earth) and energise particles already trapped in the magentosphere and radiation belts. Electrons then race down Earth’s magnetic field lines and crash into the gases at high altitudes of the atmosphere. Oxygen gives off a green colour when excited; nitrogen produces blue or red colours.

Satellite image of central Iran
Credits: OLI/Landsat 8/NASA

Vivid colours and an extraordinary range of shapes and patterns fill this satellite image of central Iran. The colours have an otherworldly look for good reason. In contrast to the natural-colour Landsat images, this is a false-colour image composed from light that is invisible to human eyes.

False-colour satellite images often have a vibrant and otherworldly look. Though they can be quite beautiful and even seem artistic, a carefully interpreted false-colour image can provide remarkable scientific insights as well.

Comparing these false and natural-colour versions of this image of the Yazd and South Khorosan provinces of Iran, it is much easier to make out the boundaries between different rock layers and formations in false colour. It is also possible to see where water flows down from the dark ridges on the western edge of the false-colour image. The streaks of green throughout the false-colour image are not representative of vegetation, but rather show the distribution of rock with a particular composition.

Credits: MODIS/Terra/NASA

Late winter storms dumped a fresh coating of snow across the Alps in mid-March 2016. The fresh powder was a welcome sight for skiers, snowboarders and the many resorts that cater to them.

Across the Alps, snow cover was late to arrive in the winter of 2015-16. Some early November snowfall - the usual start of the season - was followed by weeks of above-average temperatures. Many locations did not see substantial snow until after New Year’s day. Weather patterns grew more seasonable in January and February, and a heavy March snowfall — 40-100cm in some areas — gave hope to the winter sports industry.

This season, as well as 2014-15, fit with the long-term trend in the European Alps. For much of the 20th century, snow cover increased slightly or held steady. But in the 1980s and 90s, average winter snow cover started to decrease, and winter rainfall increased at lower altitudes. That trend has continued in the 21st century. Though the average area covered by snow in any given winter has not changed much, the depth and the duration of snow cover has decreased, particularly in the south-eastern and south-western mountains and in areas below 2,000m altitude.

Credits:ISS/NASA

The image shows angular gashes in the snow-covered landscape of north-eastern Wyoming. The astronaut’s eye was drawn to the open-cast pits of several coal mines that operate out of the small town of Gillette, which appears on the lower right. The coal lies at very shallow depth, making it economical to mine. The steep walls of the overlying rocks cast strong shadows in this snowy scene. Wind distributes coal dust so that the pits appear much darker, especially the largest pit in the view (upper left).

The port city of Haifa on Israel’s Mediterranean coast
Credits: ISS/NASA

The same astronaut probably took both of these photographs of the port city of Haifa on Israel’s Mediterranean coast. In geography training, astronauts are taught to concentrate on the shapes of coastlines because they are a first-order visual cue when circling the planet, and often uniquely shaped. The nose of Cape Karmel and the bay that protects the Port of Haifa are shapes that can tell crews where they are.

In the daylight image, the strong visual line of the coast contrasts with the subtle city colours. The steep slope of the north flank of Mount Carmel (bottom of the image), facing the port, is marked by a long, dark shadow in the mid-afternoon sunlight. Older neighbourhoods with linear roads lie on the lower slopes, closer to the port. Newer neighbourhoods show a pattern of streets that wind along the intricate edges of the canyons. In a small country where land is scarce, brown farmlands appear close to the middle of the city.

The night shot does not show the coastline, but it does show different city neighbourhoods in a way that is difficult to see in the day. The brilliant port lights contrast with somewhat dimmer residential areas. Straight roads of the older residential neighbourhoods are easily distinguished from the winding roads that follow the canyon cliffs. The industrial area just east of the port has areas of green and blue lights and a less dense street pattern. Surrounding farmlands are so dark that they can be confused with the sea.

Credits: VIIRS/Suomi NPP/NASA

A natural-colour image showing large numbers of small fires burning throughout the Indochina peninsula on 19 March 19. Notice the thick cloud of smoke that obscures much of western Thailand and eastern Myanmar.

Fire has a long history as a land management tool in south-east Asia; most of the fires detected by the satellite were likely lit intentionally. In cultivated lowlands (tan area), farmers use fire to burn crop debris after harvest and to prepare the land for the growing season. In the mountains (green), some people practice “slash and burn” to clear forested areas with fire, planting crops for a few years, and then letting brush and forest retake the fields during a fallow period intended to replenish soil nutrients. Fires are also sometimes lit to promote the growth of grasses used to make thatch roofs and brooms, to encourage the reproduction of certain mushrooms, to make seeds of some wild plant seeds germinate, and to flush out game during hunts for wildlife.

Though many of the fires were surely lit intentionally, natural conditions are potentially intensifying them and causing some to burn out of control. South-east Asia is in the midst of a drought that has parched forests and other vegetation. Observers in Vietnam are calling the drought there the worst in 90 years. The lack of rain has led to intrusions of salt water into rice paddies and other croplands along the Mekong delta. In Thailand, authorities have diverted water from the Mekong river to agricultural areas in response to the dry weather, a move that has worried neighbouring countries. In an attempt to ease tensions, China announced in March that it would release extra water into the Mekong at the Jinghong hydropower station.

The impact of sand mining on the northern reaches of Poyang Lake
Credits: Landsat 5 and OLI/Landsat 8/NASA

Over the past few decades, the global demand for construction sand has boomed, especially in Asia due to rapid urbanisation. In China alone, the demand for cement has increased 438% over the past two decades.

In 2000, dredging and other sand mining become so intensive along the Yangtze river that Chinese authorities banned the activity along the lower and middle reaches of the river. This drove many sand mining operators to Poyang Lake, a large body of water that flows into the Yangtze about 600km upstream of Shanghai.

This pair of false-colour images shows the impact of sand mining on the northern reaches of the lake. The first image was acquired in December 1995; the second image shows the same area in December 2013.

By contrasting the two images, we can see dramatic changes in the outlet channel that connects Poyang Lake to the Yangtze river. Sand removal and dredging have deepened and widened the channel significantly. These activities also have left the remaining sandbars and shores with an irregular, serrated appearance. Using infrared dat, researchers found that the lake was producing up to 236 million cubic metres of sand per year — about 9% of the total produced by China - enough to make Poyang Lake the largest sand-mining operation in the world.

Field research on wintering waterbirds the lake found that it hosted 98% of endangered Siberian cranes and oriental white storks, as well as a significant number of other endangered waterbirds.

Credits: Sentinel-3A/ESA

A long crack running through the ice shelf to the east of the centre part of the Antarctic peninsula. The crack is about 2km wide, but widens to 4 km or more in some places. There are also finer cracks and structures visible in the ice shelf.

A floating shelf of ice attached to the coast of Antarctica appears ready to shed an iceberg into the Southern Ocean
Credits: OLI/Landsat 8/NASA

A floating shelf of ice attached to the coast of Antarctica appears ready to shed an iceberg into the Southern Ocean. Over the course of two years, a small crack grew large enough to spread across nearly the entire width of the Nansen Ice Shelf.

The first image was acquired in December 2013 and second in December 2015.

These floating shelves are important for holding back the flow of ice from the interior of the continent to the sea. Ice that sloughs from a floating shelf does not raise sea level. But lose part of the ice shelf, and the seaward flow of land ice can accelerate — a phenomenon that contributes to sea-level rise.

On a map created in 1590, the area was labeled Promontorium tremendum: horrible headland, or cape terrible. Four centuries later, these barrier islands along the North Carolina coast are better known as havens for turtles and wild horses and for humans seeking a bit of tranquility by the sea.

This image of Cape Lookout national park shows swirling sediments and shallow bottoms as faint green, tan, and blue areas around the islands. The yellow line around the islands notes the official boundaries of the park.

Credits: Sentinel-2A/ESA

This false colour image brings us to Utah’s Salt Lake City, which sits at 1,300m, bordered by the waters of the Great Salt Lake and the peaks of the Wasatch Range,. The Great Salt Lake, partly visible on the left side of the image, is the largest salt-water lake in the western hemisphere.

The lighter blue areas denote solar evaporation ponds at the edges of the lake, which produce salts and brine. The lake contributes an estimated $1.3bn annually to Utah’s economy, comprising the harvesting of brine shrimp, industry in mineral extraction, and recreation. Although it has been referred to as “America’s Dead Sea”, the lake provides habitat for millions of native birds, brine shrimp, shorebirds and waterfowl.

In 1904, the Southern Pacific Causeway was built to create a shorter route across the lake, visible across the top part.

The mountains and several parks appear in varying shades of red, owing to this false-colour band combination. The scattered greys and whites visible along the centre of the image are the City of Salt Lake, home to some 190,000 people .

Credits: MODIS/Terra/NASA

Three of the major lakes in east Africa: from south-west to north-east they are the ovoid Lake Victoria, the branching Lake Kyoga and the long Lake Turkana. Several other smaller lakes also appear in this image.

It has been estimated that Africa holds about 30,000 cubic kilometers (7,197 cubic miles) of water in large lakes. This is the largest volume of water in large lakes of any continent.

Lakes are an integral and important part of human lives, serving as a source of livelihoods, recreation, and nourishment, as well as critical sources of drinking water. Lakes can also be risk factors, especially to those living near them, as they can be major sources of natural disasters (such as floods) as well as hosts to diseases and pollutants. As populations increase, more stress is putting on the natural ecosystem of a lake, often decreasing the ability of people to safely use the water or decreasing fisheries. Climate change can also dramatically damage a lake’s ecosystem, such as the dramatic drying of Lake Chad, which has lost about 90% of its former size.

Credits: Sentinel-2A /ESA

Northern Namibia’s Etosha salt pan is believed be have been a lake was first formed tens of millions of years ago. More recently – mere thousands of years ago – the Kunene river would have flowed through this area, filling the large lake before tectonic movement changed the river course. The lake then dried up, leaving behind some 4,800 sq km of exposed minerals.

The pan is a designated Ramsar wetland of international importance. It is the only known mass breeding ground for flamingos in Namibia. Built-up mounds of clay and salt throughout the pan also draw animals who use them as salt lick, including lions, elephants, leopards and even black rhinoceroses.

The straight lines cutting across the image are roads, and the one on the right side clearly delineates the border of the protected park to the south. On the northern side of the road, we can see agricultural structures.

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