Group for Earth Observation

No 75 - September 2022

July 2022 was characterised by intense, and in some parts prolonged, heatwaves which affected Europe
and the rest of the world, breaking several air temperature records. As reported in the latest Climate
Bulletin published by the Copernicus Climate Change Service (C3S), July 2022 was one of the threewarmest Julys on record globally and the sixth warmest July for Europe. This image, created using data
retrieved from C3S, shows the Surface Air Temperature Anomaly for June 2022. As highlighted by thedarkest shaded red colour, temperature anomalies reached peaks of +4ºC in Italy, France, and Spain.

Useful User Groups

GEO MANAGEMENT TEAM
General Information
John Tellick,email: information@geo-web.org.uk

GEO Newsletter Editor
Les Hamilton,
email: geoeditor@geo-web.org.uk

Technical Consultant (Hardware)David Simmons
email: tech@geo-web.org.uk

Webmaster and Website Matters

Weather Satellite Reports
This group provided weekly reports, updates and news
on the operational aspects of weather satellites.

https://groups.io/g/weather-satellite-reports

SatSignal
This end-user self help group is for users of David
Taylor’s Satellite Software Tools, including the orbit
predictor WXtrack, the file decoders GeoSatSignal and
SatSignal, the HRPT Reader program, the remapper
GroundMap, and the manager programs - MSG DataManager, GOES-ABI Manager, AVHRR Manager etc.

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Management TeamDavid Anderson
Rob Denton

MSG-1
This forum provides a dedicated area for sharing
information about hardware and software for receiving
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Nigel Evans: nigel.m0nde@gmail.com
Clive Finnis
Carol FinnisPeter GreenDavid SimmonsDavid Taylor

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wishing to exchange information relating to either GEO
or Earth Observation satellites.

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2

Les HamiltonW

hat a summer it’s been in the Northern Hemisphere this year, with heatwaves, droughts, record
high temperatures and forest ﬁres galore! A temperature of 40.3°C recorded at Coningsby,
Lincolnshire on July 19 broke the UK all-time record, the ﬁrst occasion the 40-degree mark had been
topped there, and another record was set in Spain, with 47.6°C at La Rambla meteorological stationnear Cordoba. Indeed, on that day, the only European nations that failed to record a temperature inexcess of 35°C were Iceland (30.5 °C) and Ireland (33.3 °C).

A

ll this emphasises, if ever the need were required, for mankind to address the problems of
Climate Change with the utmost urgency. And by way of contrast, with much of Europe andNorth America facing severe drought, Australia was experiencing record ﬂooding rainfall in the eastof the country. The front page image from the Copernicus Climate Change Service illustrates thetemperature anomalies over Europe this July.

A

ccording to the latest report ‘Drought in Europe - August 2022’ recently published by theEuropean Drought Observatory (EDO) of the Copernicus Emergency Management Service(CEMS), Europe is experiencing its worst drought in centuries, which is causing a severe impact on
the energy sector and on summer crop yields. Reports on pages 33 and 34 show starkly just how
badly the Rhine and Yangtze rivers have been aﬀected this summer.

Contents
Young, Active Bagana Volcano
Sea Ice in the Barents Sea, Kolguyev Island, Novaya Zemlya
Tenoumer Crater, Mauritania
Hurricane Agatha over Mexico
Europa Island
Heatwaves and Fires Scorch Europe, Africa, and Asia
Sunglint in Satellite Images
Heatwave over Western Europe
Floodwaters Reach Australia’s Channel Country
Lake Mead Keeps Dropping
Sahara’s Amazing Richat Structure
Ice Springs Lava Flow
Wildfire near Salamanca, Spain
Recent Updates to Metop Manager’s GAC Processing
Muruntau Gold Mine
Mount Etna Eruption
Summer in Iceland
Death Valley Flash Flooding
Tracking 30 Years of Sea Level Rise
Massive Algal Blooms in the Gulf of Finland
River Rhine Runs Dry
Drought Causes Yangtze to ShrinkFranz Josef Land
Lake Balkhash, Kazakhastan
Satellite Status

NASA Earth Observatory
MODIS Web Image of the Day
Les Hamilton
MODIS Web Image of the Day
NASA Earth Observatory
NASA Earth Observatory
John Tellick
Copernicus Image of the Day
MODIS Web Image of the Day
NASA Earth Observatory
Les Hamilton
NASA Earth Observatory
European Space Agency
John Tellick
NASA Earth Observatory
Copernicus Image of the Day
MODIS Web Image of the Day
NASA Earth Observatory
NASA Earth Observatory
Copernicus Image of the Day
European Space Agency
European Space Agency
MODIS Web Image of the Day
NASA Earth Observatory

www.geo-web.org.uk

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This thermal false-colour image from Metop-C, submitted by John Tellick, was acquired at 09:56 UT on August 12,
2022 illustrates heat across Europe and the UK on the hottest day of the 2nd UK heatwave on August 12th.
Image © EUMETSAT 2022

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Young, Active Bagana Volcano
NASA Earth Observatory
Story by Sara E Pratt

NASA Earth Observatory image by Joshua Stevens, using Landsat data from the U.S. Geological Survey. .

Bougainville Island in Papua New Guinea hosts three large
volcanoes along its mountainous middle: Mount Balbi,
Mount Bagana, and the Mount Takuan volcanic complex.
Of these, only Mount Bagana is currently active.
Since Bagana was first viewed by scientists in the 1840s,
it has been erupting nearly nonstop. The remote volcano
extrudes thick, blocky, slow-moving andesitic lavas. These
have built the stratovolcano to a height of 1,850 metresabove sea level. The large, symmetrical cone formed over
300 to 500 years, making it one of the youngest and mostactive volcanoes in the South Pacific. Lava descends theflanks on all sides of the volcano, forming lobes up to
50 metres thick. A small lava dome is sometimes observed
near the summit.
Since February 2000, Bagana has been in an eruptive
period, according to the Smithsonian Global Volcanism
Program. Recent lava flows are visible in this image
acquired on May 28, 2022, by the Operational Land
Imager-2 (OLI-2) on Landsat 9. The fresh lava is darkbrown, while lighter brown areas were probably strippedof vegetation by volcanic debris or acidic gases. Olderlava flows are covered in light green vegetation, and thesurrounding forests are dark green. The volcanic plume, as
well as some nearby clouds, are white.
Bagana is also a ‘remarkable emitter of sulphur dioxide’,according to recent research. The volcano belches out
several thousand tons of the air pollutant per day, the mostof any volcano in the world without a lava lake.
Such robust volcanic activity is due to the geologic setting.
In the southwest Pacific, the Australian and Pacific plates
are converging at a rate of about 11 centimetres per
year, a slow-motion collision with big consequences. As
one plate dives down below the other in a process called
subduction, a deep-sea trench forms at the leading edgeof the lower plate, and volcanoes form on the overlying
plate. But these forces are ever shifting. The island of
Bougainville formed mainly in two geologic stages. About
45 million years ago, the Pacific Plate was subducting
beneath the Australian Plate. Volcanoes began to build up
on the sea floor. Then, around 10 million years ago, thedirection of subduction changed and the Australian Plate
began to subduct beneath the Pacific Plate. This activity
produced the more recent volcanic rocks of BougainvilleIsland, and later led to the formation of Bagana Volcano.

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Sea Ice in the Barents Sea, Kolguyev Island, Novaya Zemlya
MODIS Web Image of the Day
https://modis.gsfc.nasa.gov/gallery/showall.php
As days lengthen and air temperatures increase inlate spring, the wintery covering of sea ice worn by the
Barents Sea begins to melt. With daytime temperatures inMurmansk, Russia reaching 10°C since May 6, and nighttime lows above freezing since May 10, regional melting
has become more rapid in late May 2022. Murmansk islocated to the west of the area captured in this image.
The Moderate Resolution Imaging Spectroradiometer(MODIS) on board NASA’s Terra satellite acquired thistrue-colour image of the Barents Sea on May 31. At thattime, although most of the Barents Sea was open water,

thin filigrees of floating sea ice remained visible between
the round Kolguyev Island, in the west, and the Novaya
Zemlya group of islands in the northeast. The landmass
sitting in the southeast belongs to the Zapolyarny Districtof Nenets Autonomous Okrug, Russia. Fast ice (iceclinging to a landmass) remains along Novaya Zemlya, theedges and bays of the Zapolyarny District, and in a very
few locations along the northeastern and southwesternedges of Kolguyev Island. In the far northeast, behind
Novaya Zemlya, abundant sea ice remains in the Kara
Sea, although it is cracked and thinning.

Image Credit: MODIS Land Rapid Response Team, NASA GSFC

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Tenoumer Crater, Mauritania
Les Hamilton

Figure 1 - Tenoumer Crater, Mauritania
Image: Wikimedia / Credit: Michael Dennig

Earlier this year, I was intrigued by a NASA internet article
relating to Tenoumer Crater [1]. I had never previously
heard of this feature but once I saw the image above I was
sufficiently impressed to learn all I could about it.
When the term ‘Meteor Crater’ crops up, everyone
automatically thinks of the famous Barringer Crater inArizona. Barringer is often dubbed the “Best preserved
crater on Earth”, but the secluded and largely unknown
Tenoumer Crater certainly gives it a run for its money. A
statistical comparison between the two craters is shown in
the table directly below.
Tenoumer Crater

Barringer Crater

Width1900 metres

1200 metres

Depth

200 - 300 metres

170 metres

Rim

110 metres

45 metresAge

21,400 ± 9,700 years

50,000 years

As this data clearly shows, the much younger Tenoumer
Crater, located at latitude N22°55′ and longitude W10°24′
in the western Sahara Desert in Mauritania, scores inevery category. The crater is exposed at the surface and isnearly circular with its edges rising as high as 110 metresabove the surrounding terrain. The depth of the crater isdifficult to ascertain precisely as it is buried by between
200 and 300 metres of unconsolidated sediments: as you

Figure 2 - Tenoumer Crater imaged by ESA’s
Sentinel-2 mission on May 16, 2022.
Image: modified Copernicus Sentinel data (2022),
processed by ESA, CC BY-SA 3.0 IGO

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might expect from its location in the Sahara, this sedimentis most probably largely windblown material accumulated
during the aeons since the crater formed.
Prior to 1970 there was much debate concerning theorigin of Tenoumer Crater: was it the product of vulcanismor the result of a meteorite strike? Scattered rocks in
the immediate vicinity of the crater were very similar tobasalt and rhyodacite, both of which are characteristic ofvulcanism and were formerly attributed to be evidenceof an outpouring of lava. However, the crater lies in
the Reguibat Shield, a stable peneplain consisting ofPrecambrian granite and gneiss at least two billion years
old, surfaced by a thin layer of Pliocene sediments whichwere deposited no more than a mere 2.5 million years ago.
In 1970, the crater, which is located on top of these recent
deposits was confirmed to be of meteoritic origin.
The rocks and outcrops surrounding the feature, formerly
attributed to a volcanic event, were found to contain
inclusions of the two billion year old granitic basement
rocks. These inclusions exhibited distinctive featuresconsidered to be indicative of shock-wave action andthus diagnostic for a meteorite impact, such as small
fractured glass inclusions, quartz grains exhibiting planar
deformation and partial fusion and decomposition of biotite
grains inter alia.
Figure 3 is the original image that sparked my interestin Tenoumer Crater. It was acquired by the Advanced
Spaceborne Thermal Emission and Reflection Radiometer(ASTER) instrument carried by NASA’s Terra satellite on

Figure 3 - Tenoumer Crater imaged by the ASTER instrument
aboard NASA’s Terra satellite
NASA image created by Jesse Allen, using data provided
courtesy of NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan
ASTER Science Team.

January 24, 2008. In this simulated true colour image,the arid landscape appears in varying shades of brick
red, brown, and tan. The crater’s outline is unmistakable,
yet doesn’t necessarily look like a crater; the light andshadows make it look more as if someone has pressed a
giant cookie cutter into the rock. In this image, the sunlightshines from the southeast (lower right), and the brightarc along the northwestern part of the crater is where thecrater walls slope up to the rim. Elsewhere around theperimeter, the relatively steep walls cast dark shadows.

Figure 4 - A view over the sediment-filled crater
Credit: unknown

References
1
2
3
4
5

https://www.earthobservatory.nasa.gov/images/8536/tenoumer-crater-mauritania
https://www.esa.int/ESA_Multimedia/Images/2022/06/Tenoumer_Crater_Mauritania
https://en.wikipedia.org/wiki/Tenoumer_crater
https://www.anews.com.tr/life/2022/07/03/incredible-image-of-tenoumer-one-of-the-best-preserved-craters-in-the-world
https://www.wondermondo.com/tenoumer-crater/

www.geo-web.org.uk

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Hurricane Agatha over Mexico
MODIS Web Image of the Day
https://modis.gsfc.nasa.gov/gallery/showall.php
Hurricane season in the eastern Pacific arrived to an
early and potent start. Though May storms are rare
there, Hurricane Agatha struck western Mexico, near
Puerto Escondido, bearing maximum sustained windsof 169 kilometres per hour on May 30, 2022. That madethe Category 2 storm the strongest May hurricane to
make landfall along the Pacific coast of Mexico sincemodern record keeping began in 1949, according to the
National Hurricane Center (NHC). Agatha was only thethird hurricane to make landfall in Mexico during themonth of May.

terrain of southern Mexico. The strong winds anddrenching rain triggered landslides and, as of theevening of May 31, ten people had been reported killed
in Oaxaca, Mexico with another 20 people missing.

The Moderate Resolution Imaging Spectroradiometer(MODIS) on board NASA’s Aqua satellite acquired atrue-colour image of Hurricane Agatha on May 30,
2022, as the storm was making landfall over Mexico.
Agatha brought intense downpours and howling winds
to several tourist beaches and fishing towns in anotherwise sparsely-populated region before weakening
rapidly as it moved northward over the mountainous

The eastern Pacific hurricane season officially runs fromMay 15 through November 30 with the peak monthsof the season from July through September. NOAA’s
seasonal outlook for the eastern Pacific hurricane
season in 2022 indicates that a below-normal season is
likely. The Atlantic hurricane season begins on June 1
and ends November 30, and the seasonal outlook there
predicts a more active season than normal.

At 11:00 am EDT on May 31, the NHC issued its
final advisory on Agatha, stating that the storm had
dissipated over the rugged terrain of southeastern
Mexico. At that time, they forecast that heavy rains fromthe remnants of Agatha could precipitate up to 40 cm onparts of Mexico.

Image Credit: MODIS Land Rapid Response Team, NASA GSFC

www.geo-web.org.uk

9Europa Island
NASA Earth Observatory
Story by Kathryn Hansen

NASA Earth Observatory images by Lauren Dauphin, using Landsat data from the U.S. Geological Survey.

Several volcanic seamounts andhundreds of volcanic cones rise
above the floor of the southern
Mozambique Channel. A few of thelarger volcanic features are cappedwith flat expanses of carbonate thatbreach the water’s surface, forming
low-lying coralline islands. Europa is
one such island.
Europa Island is the focus of thisimage, acquired on April 3, 2022,with the Operational Land Imager-2(OLI-2) on Landsat 9. It is partof an overseas French territorythat includes the Îles Éparses,
or ‘scattered islands,’ dispersed
around Madagascar. Mozambiqueon the African mainland lies about
500 kilometres to the west, andMadagascar sits about 300 kilometresto the east.
Europa Island spans about 28 square
kilometres, making it the largest ofthe Îles Éparses. It was initially anatoll that became exposed at the sea
surface around 90,000 years ago.
The atoll progressively filled in, and it
slowly transformed into the island weknow today. A belt of nearly pristinecoral reefs now hugs the coastline.
These ‘fringing’ reefs span about 18
square kilometres, with a healthy 80%
coverage of live corals. An abundanceof fish, including sharks, cruise thereefs.
Another important habitat—the Grand
Lagoon—cuts far into the island.
Saltwater mangroves dominate thelagoon’s shoreline, while a sandy
beach covers its western side. This
beach, the lagoon, and the island’s
shore all support each life stage of theisland’s numerous sea turtles. Europa
has been called the largest nestingsite for green turtles in the Western
Indian Ocean.
Vegetation across much of the island
has probably not changed much sincewww.geo-web.org.uk

naturalists started visiting in the early
20th century. Dry forests still growalong the oldest and highest partsof the island, where the ground isrocky. Herbaceous plants and grasses
spring from the newer surfaces thatrise just a few centimetres above sea
level, and bushes prefer the coastal
areas. The native vegetation provides
critical breeding habitat for seabirds,
including the red-tailed tropicbird, thered-footed booby, and the great andlesser frigatebird.
The most obvious evidence ofhuman activity in these images are
an airstrip, built in 1973 when amilitary camp was established, andthe nearby sisal plantation planted bya family that attempted to settle on
the island in the early 1900s. Several
attempts to settle on the island since1860 have failed, possibly because of
the lack of fresh water. Today the only
human presence is the French military
and the occasional visiting scientist.

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Heatwaves and Fires Scorch Europe, Africa, and Asia
NASA Earth Observatory
Story by Sara E. Pratt

Figure 1 -Temperature map for July 13, 2022
NASA Earth Observatory image by Joshua Stevens, using GEOS-5
data from the Global Modeling and Assimilation Office at NASA GSFC.

In June and July 2022, heatwaves struck Europe, North
Africa, the Middle East, and Asia, as temperatures climbed
above 40°C in places and broke many long-standing
records.

Figure 1 shows a model of air temperatures acrossmost of the Eastern Hemisphere on July 13. The data
come from the Goddard Earth Observing System Model,
Version 5 (GEOS-5), a global atmospheric model that uses
continued overleaf

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Figure 2 -Fire detections in the Iberian peninsula on July 12, 2022.
NASA Earth Observatory image by Joshua Stevens, using VIIRS day-night
band data from the Suomi National Polar-orbiting Partnership.

mathematical equations to represent physical processes
near the surface and in the atmosphere.
In Western Europe, which was already experiencing
severe drought, the heatwave fuelled fires that raged
across Portugal, Spain, and parts of France. In Portugal,
temperatures reached 45°C in the town of Leiria, wheremore than 3,000 hectares had burned. More than halfof the country was on red alert as firefighters battled
14 active fires.
Figure 2 shows the locations of fire detections in Portugal
and Spain as observed by the Visible Infrared Imaging
Radiometer Suite (VIIRS) on the Suomi NPP satellite on
July 12. The prominent fire detections west of Madrid
include the town of Las Hurdes where more than 1,500
hectares were burned.
In Italy, the record heat contributed to the July 3 collapseof a portion of the Marmolada Glacier in the Dolomites.

The avalanche of snow, ice, and rock killed 11 hikers.
In the U.K., the Met Office issued extreme heat or amber
warnings as temperatures were expected to continue toclimb, possibly breaking all-time highs.
In North Africa, Tunisia endured a heatwave and fires
that damaged the country’s grain crop. On July 13,
in the capital city of Tunis, the temperature reached
48°C, breaking a 40-year record. In Iran, temperatures
remained high in July after reaching a scorching 52°C inlate June.
In China, the summer has brought three heatwaves thathave buckled roads, melted tar, and popped off roof tiles.
The Shanghai Xujiahui Observatory, where records havebeen kept since 1873, recorded its highest temperature
ever: 40.9°C on July 13. High humidity and dewpoints,
along with warm overnight temperatures, createdpotentially deadly conditions.

www.geo-web.org.uk

12Sunglint in Satellite Images
John Tellick
One thing that Earth Observation Satellites—particularly
polar orbiting ones—suffer from at certain times of the year
is sun glint. This has been particularly in evidence in recent
NOAA-19 images.
Sunglint occurs when the suns’ rays are reflected into
the satellite’s radiometer from a still watery surface: seas,lakes, rivers etc. on the Earth below.
Still water in the ocean acts as a mirror, and when the sun,‘water mirror’ and satellite are at a particular angle to one
another, sunglint occurs. When a ray of light hits a mirror
at an angle, it always reflects away from the mirror at an
identical angle: it is this self-same process that produces
the sunglint observed in satellite images.
The sun glint area will look silvery and bright but whereareas of water in the same image are rough, they do notreflect sunlight evenly and the area will appear dark.

I have used RGB [Red, Green, Blue] processing of three
wavelengths to produce the accompanying images fromNOAA-19. This tends to make them rather colourful but
does show up sun glint really well compared to a normal
false colour image.
As the sun glint area on NOAA-19 descending images isover to the east side of the satellite pass (looking north)
it is in the area of the satellite scan which suffers fromdistortion resulting from the curvature of the Earth, so
the image has been geographically corrected—to lookright. This results in stretching of that area of the image,and thus results in a lower resolution of that specificgeographical area.
This sun glint phenomenon is common on polar orbiting
satellites but can also sometimes be seen over the world’s
oceans on geostationary satellite images, especially when
the Sun is directly above—or close to—the Equator.

This NOAA 19 image captured on July 22, 2022 shows spectacular sunglint over the Mediterranean Sea and on thewaters of the River Rhône flowing into it from the north.
Image received via EUMETCast and processed with David Taylor’s EARS AVHRR Manager and HRPT Reader.

www.geo-web.org.uk

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This NOAA 19 image was captured on July 17, 2022. With the sun to the east of the satellite’s scan, this RGB image displays
spectacular sun glint over the Adriatic and Tyrrhenian seas. NOAA-19 used to be the operational local midday ascending pass satellite
but its orbit has drifted considerably since its launch in 2009 and it now descends in the early morning, around 07:00 UT.
Image © EUMETSAT 2022

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Heatwave over Western Europe
Copernicus image of the day
https://www.copernicus.eu/en/media/image-day

Credit: European Union, Copernicus Sentinel-3 imagery

An extreme heatwave occurred over western Europe during mid July 2022, with many temperature records being
broken in Portugal and Spain. According to the national meteorological organisation of Portugal (IPMA), the Pinhão
weather station recorded an air temperature of 47.0°C on July 14, setting a new July record for the country. The
previous maximum value for the month was 46.5°C, reached in Amareleja, Alentejo, in 1995. On July 12, the city ofOurense in northwestern Spain set its all-time temperature record with 43.2°C.
The Land Surface Temperature (LST) in some areas of Spain exceeded 59°C and reached 48°C in southern France on
July 142, as highlighted in this data visualisation of measurements from the Copernicus Sentinel-3 Sea and Land Surface
Temperature Radiometer (SLSTR) instrument.
Note
The LST is the temperature of the soil and should not be confused with air temperature. However, the high airtemperatures are reflected in land surface temperature values.
The Copernicus Sentinel-3 mission is composed of two twin satellites (Sentinel-3A and Sentinel-3B) both equipped with
the SLSTR, an instrument whose main objective is to provide Sea and Land Surface Temperature (SST, LST).

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Floodwaters Reach Australia’s Channel Country
MODIS Web Image of the Day
https://modis.gsfc.nasa.gov/gallery/showall.php

Image Credit: MODIS Land Rapid Response Team, NASA GSFC

Torrential rains over eastern Australia brought severe
flooding to parts of Queensland and New South Wales inearly March 2022. Media reported that tens of thousandsof residents along the southeastern Australia coast had
been evacuated, with about 1,000 rescues in New South
Wales by March 1. According to AccuWeather, the cityof Brisbane received more than 600 mm of rain in thethree-day period February 24-27, setting the record for
its wettest three-day period since weather data tracking
begin in 1840. According to the Center for Disaster
Philanthropy, the Insurance Council of Australia extended
the area declared an insurance catastrophe from southeast Queensland into northern New South Wales in orderto help prioritise handling more than 15,000 claims that
had already been lodged by March 1.
While the floods were nothing short of catastrophic
across the coastal regions, the flooding brought water
trickling inland, even to Australia’s Channel Country—anarea so named because of the dry riverbeds (channels)that mark the arid interior area. The region is also known
for its ephemeral lakes, which are dry (or nearly so) mostof the year. Channel Country flooding is a fairly common
occurrence at the end of summer, but this year’s massive
flooding has brought large amounts of water to theregion.
On March 3, the Moderate Resolution Imaging
Spectroradiometer (MODIS) on board NASA’s Aqua
satellite acquired this false colour image of flooding in the
Channel Country of southwestern Queensland. This typeof image is particularly useful to separate out deep water(deep blue) and shallow water or moist salt flats (lightblue) from dry land (brown) and vegetation (bright green).
This image shows water in Lakes Machattie, Mipia andKoolivoo. The floodplains of the Georgina River and Eyre
Creek are flushed with green vegetation far northward,
heading into the Northern Territory.

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Lake Mead Keeps Dropping
NASA Earth Observatory
Story by Michael Carlowicz

Continuing a 22-year downward
trend, water levels in Lake Meadstand at their lowest since April
1937, when the reservoir was still
being filled for the first time. As
of July 18, 2022, Lake Mead wasfilled to just 27% capacity.
This largest reservoir in the UnitedStates supplies water to millions
of people across seven states,
tribal lands, and northern Mexico.
It now also provides a stark
illustration of climate change anda long-term drought that may be
the worst in the US West in 12
centuries.
The low water level comes attime when 74% of nine Westernstates face some level of drought;
35% of the area is in extreme or
exceptional drought. In Colorado,
location of the headwaters of theColorado River, 83% of the state
is now in drought, and the snow
pack from last winter was below
average in many places.

Figure 1
Lake Mead imaged by Landsat-7 in July 2000
NASA Earth Observatory images by Lauren Dauphin, using
Landsat data from the U.S. Geological Survey

The natural-colour images infigures 1 and 2 were acquired on
July 6, 2000, and July 3, 2022,
by Landsat 7 and Landsat 8.
The detailed images in figure 3(overleaf) also include a view
from Landsat 8 on July 8, 2021
(middle). The light-coloured fringes
along the shorelines in 2021 and2022 are mineralised areas ofthe lake shore that were formerly
underwater when the reservoir
was filled closer to capacity. The
phenomenon is often referred toas a ‘bathtub ring.’
The lake elevation data (figure 4)
come from the US Bureau of
Reclamation (USBR), which
manages Lake Mead, Lake Powell,and other portions of the Colorado
River watershed.
As of July 18, 2022, the water
elevation at the Hoover Dam was
317.4 metres above sea level,

Figure 2
Lake Mead imaged by Landsat-8 in July 2022
NASA Earth Observatory images by Lauren Dauphin, using
Landsat data from the U.S. Geological Survey

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17

whereas the water elevation
twenty years earlier at the end of
July 2000 (around the time of theLandsat 7 image above) was 341
metres. Lake levels at the dam
should stay above 305 metres tocontinue operating hydropower
turbines at normal levels.
At maximum capacity, Lake Meadwould reach an elevation 372
metres near the dam and would
hold 36 trillion litres of water. The
lake last approached full capacity
in the summers of 1983 and1999.
About 10% of the water in
Lake Mead comes from local
precipitation and groundwatereach year, with the rest comingfrom snow melt in the Rocky
Mountains that flows down the
Colorado River watershed throughLake Powell, Glen Canyon, and
the Grand Canyon.
The Colorado River basin ismanaged by USBR and otheragencies to provide electric power
and water to roughly forty million
people—most notably the cities of
San Diego, Las Vegas, Phoenix,
Los Angeles—and four to fivemillion acres of farmland in theSouthwest.

July 6, 2000

July 8, 2021

July 3, 2022

Figure 3 - Comparison images: Lake Mead imaged byLandsat-8 in July 2022
NASA Earth Observatory images by Lauren Dauphin, using
Landsat data from the U.S. Geological Survey

The river water is allotted tostates (including tribal lands) andMexico through laws like the 1922
Colorado River Compact.
Above Lake Mead, Lake Powell
is currently filled to just 27% of
capacity, and the entire Coloradoriver system stands at 35%. USBR
announced in August 2021 thatstate water allocations would be
cut in 2022; further modelling andnegotiation is underway for 2023
allocations.
In June 2022, USBR issued an
emergency request to the Colorado
River basin states to reduce water
usage by 2 million to 4 million
acre-feet over the next 18 months.
In addition to serving as a major
drinking and irrigation source for
the Southwest, Lake Mead is anational recreation area that isFigure 4
Lake elevation data at the Hoover Dam for Lake Mead for 2000-2022
Lake elevation data from the Bureau of Reclamation

particularly popular with boaters.
According to the National Park
Service, five of six boating ramps/
launches are now closed.
“Declining water levels due toclimate change and 20 years ofongoing drought have reshaped
the park’s shorelines,”www.geo-web.org.uk

stated the Park Service on its
website.
“As Lake Mead continues
to recede, extending launchramps becomes more difficultand more expensive due tothe topography and projected
decline in water levels.”

18This high-resolution image acquired from Meteor M2 on June 10, 2022, was provided by Enrico Gobbettiwww.geo-web.org.uk

19

Sahara’s Amazing Richat Structure
Les Hamilton

While researching the Tenoumer Crater article(page 7), I was reminded of having seen in thepast articles relating to yet another circular featurein Saharan Mauritania: the Richat Structure, often
dubbed ‘The Eye of the Sahara’ on account of
its almost perfectly circular outline. But whereas
Tenoumer crater is a mere 1.9 kilometres across,Richat is a much larger feature, with a diameter ofsome 48 kilometres.
Richat attracted the attention of astronauts James
McDivitt and Edward White aboard the Gemini IV
mission that spent four days in orbit following lift-off
on June 3, 1965, who became the first astronauts
to photograph the structure from space. The image
opposite, a more recent, better quality one, illustrates
the unusual blue colouration of the Structure whichsomewhat resembles the appearance of a giant
ammonite fossil.
In actual fact the Richat Structure had originallybeen identified through ground-based exploration as
early as the 1930s when it was initially considered tohave been the result of a meteorite impact. But fromthe late 1940s onward, once it had been establishedthat there was no evidence whatever on the groundof the shock metamorphism and deformations
that result from an extraterrestrial impact, geologic
investigations established that the structure wasin fact a heavily eroded, slightly elliptical dome of
predominately sedimentary rocks, uplifted between
approximately 500 and 400 million years ago as aresult of pressure by molten magma from below.
After the layers of sedimentary rock were elevated,
millennia of constant weathering gradually levelledthem to expose the structure’s distinctive concentricrings. These near circular ridges and valleys are
known as cuestas (unsymmetrical ridges featuring astrong slope or escarpment on one side and a gentle
slope on the other, and resulted from differential
erosion of alternating hard and soft rock layers within
the uplifted dome. Tellingly, the rocks in the centreof the Richat structure are the oldest, trending toyounger material towards its rim, precisely what
is to be expected following the erosion to a nearlevel plain of a domed anticline. There are more
photographs of the Richat Structure overleaf.

This image of the ‘Eye of the Sahara’ was acquired on October 7,2000 by the advanced Spaceborne Thermal Emission and Reflection
Radiometer (ASTER) on NASA’s Terra satellite.
Credit: NASA/GSFC/MITI/ERSDAC/JAROS, and U.S./Japan ASTER
Science Team

This Astronaut photograph ISS030-E-12516 dating from December 17,
2011, shows fine detail of the Richat Structure.
Observations Facility and the Earth Science and Remote Sensing Unit,
Johnson Space Center.

Source References
1 The Eye of Sahara
https://earthobservatory.nasa.gov/images/150060/the-eye-of-sahara
2 Richat Structure
https://earthobservatory.nasa.gov/images/92071/richat-structure
3 Richat Structure
https://en.wikipedia.org/wiki/Richat_Structure
4 Strange Marvels
https://thedebrief.org/the-mysterious-eye-of-the-sahara-is-one-of-earths-strangest-marvels/

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20

This Astronaut photograph (ISS063-E-43607) was acquired on July 10, 2020 and shows
the Richat Structure against brightly coloured Saharan dune fields.
Credit: Earth Science and Remote Sensing Unit, Johnson Space Center.

This photograph shows terrain within the Richat Structure’s inner ring.
Credit: Clemens Schmillen / Wikimedia
This image file is licensed under the Creative Commons Attribution-Share Alike 4.0 International license.

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21

Ice Springs Lava Flow
NASA Earth Observatory
Story by Sara E. Pratt

The Ice Springs lava flow lies about 16 kilometres
west of the town of Fillmore, Utah, in the Black Rock
Desert. It was named for the icehouse conditions
found within its natural cavities, where year-roundice provided natural cold storage for farmers in thedays before refrigeration.

Bonneville. A precursor to the Great Salt Lake, Lake
Bonneville occupied basins in northeastern Nevada,western Utah, and southeastern Idaho in the late
Pleistocene Epoch, from 25,000 to 10,000 years ago.
At its greatest extent, the lake was up to 300 metres
deep and covered about 52,000 square kilometres.

The black basalt of the Ice Springs lava flow is visible
in the image below, acquired on July 12, 2022, by
the Operational Land Imager-2 (OLI-2) on Landsat 9.
Soil and vegetation have not yet taken hold onthese young rocks. The last lava flowed from the Ice
Springs vent about 700 years ago, making the jagged
basaltic aa lava the newest rock in Utah.

The darker brown areas in the image are older lava
flows, along with the sediments deposited atop themwhen they sat at the bottom of Lake Bonneville. In
some places, the contact between the younger andolder lava flows appears almost linear; this is where
the lava flowed up against a fault scarp. The lightest
brown areas are more recent sand dunes.

A total of about 540 million cubic metres of lava
have erupted here from four cinder cone volcanoes,
for which the area is also known as The Cinders.

One of the cinder cones, Red Dome, is the site ofUtah’s largest open-pit lava-rock mine. Lava, cinder,
pumice, and scoria rock have been mined here sincethe 1930s for use in landscaping, road construction,
the manufacture of cinder blocks and cement, and toline BBQ grills and fish tanks.

The 45-square-kilometre Ice Springs lava flow
erupted on to older lava flows, which erupted on
the shores and under the surface of ancient Lake

NASA Earth Observatory image by Joshua Stevens, using Landsat data from the U.S. Geological Survey.

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22

Wildfire near Salamanca, Spain
European Space Aency

This Copernicus Sentinel-2 image shows Las Batuecas—Sierra de Francia Nature Reserve near Salamanca in western Spain.
The image was acquired on 13 July 2022 and shows the wildfire affecting the area. The satellite’s shortwave infrared channel
was used to highlight heat from the wildfire. According to regional authorities, more than 4000 hectares of land had been burnedand 600 people had to be evacuated. In response to the emergency, the Copernicus Emergency Mapping Service was activated.
This service uses satellite observations to help civil protection authorities and, in cases of disaster, the international humanitariancommunity, respond to emergencies.
Image contains modified Copernicus Sentinel data (2022), processed by ESA, CC BY-SA 3.0 IGO

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23

Recent Updates to Metop Manager’s GAC Processing
John Tellick

Figure 1 - This full Earth GAC composite image was created from NOAA-19 data acquired on November 5, 2016.

Many years ago now, NOAA-19 used to be a ‘local
midday’ ascending satellite, allowing users to obtainwell lit APT images from it, and in addition excellent
GAC RGB image composites. The example above,
acquired in November 2016 was typical, albeit withsome inevitable loss of illumination over the Arctic atthat time of year.
Somehow, unnoticed by many it seems, NOAA‑19’sorbit started drifting out of its midday ascending
mode: its ‘daylight image’ became less well lit and
the GAC composites began to suffer problems.
David Taylor addressed this problem by reconfiguring
the GAC processing in Metop Manager to process
the ascending orbit IR channel only. This did work
well, but the monochrome images didn’t have thesame appeal as the coloured composites.
However, several months ago this year I noticed
that, as NOAA-19’s orbit continued its onward drift,
the satellite’s current morning descending visible
imagery was becoming better illuminated, although
there was a considerable difference in image levels
across the images from east to west. Being an‘early morning’ pass, the Sun was to the east of thesatellite’s scan.
But as spring advanced into summer, with theSun heading northwards, this disparity reduced

as the westerly illumination improved. I got intouch with David Taylor to ask if he would consider
reconfiguring the current version of Metop Manager
to once again run RGB GAC—however this would
mean altering the processing from ascending todescending orbits. Despite being busy with otherprojects, David kindly not only made the change but
sent me a beta version to test. This new version now
offered the choice of creating either RGB descendingor IR-only ascending pass GAC composite images.
Both options proved to work well but the last few
image chunks in the Southern Hemisphere RGB
image were missing— there was no daylight in that
region at this time of year. Again, David considered
this problem and ascertained that the software hada ‘no daylight level cut‑off point’ which prevented itfrom adding these ‘dark chunks.’
This was soon rectified and full RGB and single
channel IR processing options became available in
the following program version update. The result canbe seen in figure 2 (overleaf) on a NOAA‑19 RGB
GAC composite image created from data acquiredon July 22 this year.
My thanks to David Taylor for his help duringthat busy period with EUMETCast channel
reconfigurations and as usual, his willingness to offer
advice on other technical problems.

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24

Figure 2 - This full Earth GAC composite image was created from NOAA-19 data acquired on July 22, 2022.

Heatwave in the Arctic causes intense ice cap melting in Svalbard
Copernicus Image of the Day

Credit: European Union, Copernicus Sentinel-2 imagery

The extremely high temperatures recorded in this summerof 2022 are also affecting the Arctic. As of August 1,
2022, in Norway’s Svalbard archipelago, situated north ofmainland Europe, the recorded temperatures are about
5°C higher than the reference values (the 1981-2010
average for the same day). This heatwave is causing
exceptional levels of ice cap melting, thus contributing to
sea level rise.

This image, acquired by one of the Copernicus Sentinel-2
satellites on 31 July 2022, shows a large sediment
discharge in the Arctic Ocean, off the coast of Svalbard,caused by the rapid melting of snow and ice.
Data acquired by the Copernicus Sentinel satellites areused to detect changes in the Earth’s surface with great
detail and monitor the effects of climate change on remoteenvironments such as the Arctic region.

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25

Muruntau Gold Mine
NASA Earth Observatory
Story by Adam Voiland

In satellite images of central Uzbekistan, a large
circular cavity stands out amidst fields of sandand dusty plains. It is Muruntau gold mine, oneof the world’s largest sources of gold.
On July 22, 2022, the Operational Land Imager (OLI)
on Landsat 8 acquired this natural-colour image ofthe mine. Hundreds of trucks and a conveyer system
are used to transport ore to nearby processing
facilities. Workers then use a process called heap
leaching to extract gold and other precious metals.
The mine taps into the Muruntau gold deposit,
thought to be one of the largest single gold deposits
on Earth. The deposit was discovered in 1958, andmining began in 1967. The pit is now 3.5 kilometreswide and 600 meters deep. In 2021, the mine
produced as much as 3 million ounces (85,000
kilograms) of gold.
According to geologists, gold is near the surface
in this area due to a chain of events that spanned

many millions of years. Among them the closure ofan ancient ocean; a period of mountain building;intrusions of granite and water into key rockformations; and the onset of movement along nearby
faults.
Astronomers are investigating how gold ended up on
our planet in the first place. While nuclear fusion
within the Sun can synthesise many elements, theprocess does not produce enough energy to create
heavy elements like gold. Some astronomers thinkthat collisions between neutron stars and supernova
explosions may have provided that energy.
Any gold on the planet early in Earth’s history
would have sunk toward the core, but intense
bombardment by meteorites about four billion years
ago probably stirred things up and pushed small
amounts of the metal into the mantle and toward
the surface. By one estimate, gold makes up only
0.000004 percent of Earth’s crust. About 80% of
known gold reserves have already been mined.

NASA Earth Observatory image by Joshua Stevens, using Landsat data from the U.S. Geological Survey.

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26

Mount Etna Eruption
Copernicus image of the day
https://www.copernicus.eu/en/media/image-day

This image was captured by the Copernicus Sentinel-2 mission on 6 June 2022 and shows the latest activity
in Italy’s Mount Etna—one of the world’s most active volcano. The image has been processed using themission’s shortwave-infrared band to show the ongoing activity in the crater.
Credit: European Union, Copernicus Sentinel-2 imagery

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27

Summer in Iceland
MODIS WEB Image of the Day

On August 5, 2022, the cloudlayer that frequently covers
Iceland parted, allowing theModerate Resolution Imaging
Spectroradiometer (MODIS) on
board NASA’s Aqua satellite
to acquire this gorgeous truecolour image of a sunny Icelandic
summer day.
True to its name, Iceland’s
winters are long and snow-laden.
However, the island’s location andrelatively gentle maritime climate
produce summers warm enoughto melt all except about 10% of
the country’s winter coat of white.
This 10% of the country remains
covered with year-round glaciersand ice caps.
The largest ice cap Vatnajökull,
is located near the southeast
coast and is truly spectacular.
It stretches across an area of
8,100 square kilometres, whichis slightly larger than the areaof the U.S. states of Delawareand Rhode Island combined.
About thirty outlet glaciers
flow from Vatnajökull’s ice cap.
One of these long glaciers is
Breidamerkurjokull, which ends in
Jokulsarlon glacial lagoon which
can be seen off the southeast
section of Vatnajökull.
Two smaller ice caps Langjökull
and Hofsjökull can be seen in
the central highlands. Snow andglaciers also sit in the highlandsof northwest Iceland. The cold
currents flowing off the shores
tend to keep the northwesternsection of Iceland colder than therest of the island.
A gray area in the southwest
section of Vatnajökull is atypicaland appears to be caused byrecently-deposited dust and sand.
In July 2022, the white cap was
suddenly stained with gray andbrown. How the colour got there is
not quite what you would expect
on a damp, icy island.

Image Credit: MODIS Land Rapid Response Team, NASA GSFC

Ash from volcanic eruptions has
darkened Vatnajökull periodicallyin the past. But in July 2022,
the volcanoes of Iceland were
all quiet. Instead, windstorms
probably lofted sand and mineral
dust from the ground on to theice cap. Scientists have estimatedthat about 4.5 million tonnes ofdust comes to rest atop Iceland’s
glaciers every year.
Iceland’s climate is neither hot
nor dry, but it can still be a dusty
place. On average, the country
sees 135 ‘dust days’ in which atleast one weather station on theisland detects dust. Much of itcomes from heavily eroded areas

www.geo-web.org.uk

at the fronts of glaciers, but also
from sandy deserts. Together
these dusty surfaces cover nearlya quarter of the country.
The abundant dust and frequent
strong winds result in several
significant dust storms each year.
Some of the particles are lofted
all the way to Greenland and its
ice sheet but much of it stays
local to Iceland. Thin layers ofdust can reduce the amount oflight that the ice cap reflects backto space—leading to a cascadeof effects, including melting. In
contrast, thicker layers of ash
can actually insulate the ice frommelting.

28

Death Valley Flash Flooding
NASA Earth Observatory
Story by Sara E. Pratt

Death Valley before the rainfall on July 11, 2022
Death Valley after the deluge on September 7, 2022
NASA Earth Observatory image by Lauren Dauphin, using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview.

In early August 2022, flash floods soaked Furnace Creek
in Death Valley, the driest place in North America. In
just three hours on August 5, a thousand-year rainfall
event dropped 75% of the local average annual rainfall(5 centimetres). Flood water washed debris over roads,
swept away and buried cars, knocked a water facility
offline, damaged buildings, and stranded about a thousand
visitors and staff in Death Valley National Park.
The deluge dropped 3.71 centimetres, which came close
to breaking the single-day record for highest rainfall everreceived in the park; 3.73 cm in April 1988. It did, however,break the record for the most rain recorded in August,which averages just 0.25 centimetre for the whole month.
By August 6, the flood water had mostly receded, andthe stranded visitors were able to exit the park escorted
by National Park Service personnel. But extensive mud
and gravel deposits still remained, leaving some roads
impassable; they were expected to remain closed into midAugust, according to a statement by the Park Service.
Some of the flood water is visible in the latter of this pair offalse-colour images acquired by the Moderate Resolution
Imaging Spectroradiometer (MODIS) on NASA’s Terra
and Aqua satellites on July 11 and August 7, 2022. The

false-colour images were composed from a combination of
infrared and visible light (MODIS bands 7-2-1), to make iteasier to distinguish the water. Flood water appears dark
blue; saturated soil is light blue; vegetation is bright green;
and bare ground is brown.
At 86 metres below sea level, you might expect Death
Valley to be filled with water. But the desert is subject toa rain shadow effect, as humid air masses travelling east
from the Pacific Ocean must cross four mountain ranges
before they reach the desert valley. As the air masses areforced up and over the mountains, the moisture they carrycondenses, falling as rain on the western slopes, leaving a
dry area—a rain shadow—on the eastern side. By the time
most air masses reach Death Valley, they are bone dry.
On rare occasions, the lowest spot in the valley fills with awide, shallow lake, dubbed Lake Badwater. Extreme heat
and aridity usually evaporate the ephemeral lake quickly,
returning the valley floor to a salt-caked playa.
Summer temperatures in Death Valley National Park cansoar to 49°C. The highest air temperature in world history,
57°C, was recorded at Furnace Creek on July 10, 1913.
The second-hottest temperature ever recorded in the park,
54°C, occurred on August 16, 2020.

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29

This August 11, 2022 image from Metop-C depicts the British Isles and western Europe in the grip of the second summer heatwaveof the year. Almost everywhere, temperatures range from the mid 30s Celsius up into the mid 40s as wildfires proliferate and drought
conditions are declared.
Image: NOAA CLASS Archive.

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30

Tracking 30 Years of Sea Level Rise
NASA Earth Oservatory
Story by Michael Carlowicz

Figure 1
A graph of sea-level rise is shown superimposed on a globe of Earth where shadesof red over the oceans indicate where ocean level rise has been confirmed.
Earth Observatory image by Joshua Stevens, using TOPEX/Poseidon data courtesy of Josh Willis/JPL-Caltech.

Thirty years ago, scientists and engineers launched a newsatellite to study the rising and falling of seas over time, atask that once could only be done from the coast.
TOPEX/Poseidon rocketed into space on August
10, 1992, and started a 30-year record of ocean surface
height around the world. The observations have confirmed
on a global scale what scientists previously saw from theshoreline: the seas are rising, and the pace is quickening.
Scientists have found that global mean sea level—shownin the line plot above—has risen 10.1 centimetres since1992. Over the past 140 years, satellites and tide gauges
together show that global sea level has risen between 21
and 24 centimetres.
Starting with TOPEX/Poseidon, NASA and partner space
agencies have flown a continuous series of satellites
that use radar altimeters to monitor ocean surface
topography—essentially, the vertical shape and height ofthe ocean. Radar altimeters continually send out pulses ofradio waves (microwaves) that reflect off the ocean surface
back toward the satellite. The instruments calculate thetime it takes for the signal to return, while also tracking
the precise location of the satellite in space. From this,scientists derive the height of the sea surface directly
underneath the satellite.

Since 1992, five missions with similar altimeters haverepeated the same orbit every 10 days: TOPEX/Poseidon(1992 to 2006), Jason-1 (2001 to 2013), the Ocean
Surface Topography Mission/Jason-2 (2008 to 2019),
Jason-3 (2016 to present), and Sentinel-6 Michael
Freilich (2020 to present). The missions were built
through various partnerships between NASA, France’s
Centre National d’Etudes Spatiales (CNES), the European
Organisation for the Exploitation of Meteorological
Satellites (EUMETSAT), the European Space Agency(ESA), and the U.S. National Oceanic and Atmospheric
Administration (NOAA).
Together, the mission teams have assembled a unified,standardised ocean topography record that is equivalent
to the work of a half-million tide gauges. The scientists
accumulated and corroborated a data record that is now
long enough and sensitive enough to detect global andregional sea level changes beyond the seasonal, yearly,
and decadal cycles that naturally occur.
“With 30 years of data, we can finally see what ahuge impact we have on the Earth’s climate,” said
Josh Willis, an oceanographer at the Jet Propulsion
Laboratory and NASA’s project scientist for Sentinel-6
Michael Freilich. “The rise of sea level caused byhuman interference with the climate now dwarfs the

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31

natural cycles. And it is happening faster and fasterevery decade.”
The map in figure1 shows global trends in sea level as
observed from 1993 to 2022 by TOPEX/Poseidon, thethree Jason missions, and Sentinel-6 Michael Freilich.
Note the spatial variations in the rate of sea level rise,with some parts of the ocean rising faster (depicted in
red and deep orange) than the global rate. Many of theanomalies reflect long-term shifts in ocean currents andheat distribution.
The altimetry data also show that the rate of sea level riseis accelerating. Over the course of the 20th century, global
mean sea level rose at about 1.5 millimetres per year. By
the early 1990s, it was about 2.5 mm per year. Over the
past decade, the rate has increased to 3.9 mm per year.
In the line plot, the highs and lows each year arecaused by the exchange of water between the landand sea. “Winter rain and snowfall in the northernhemisphere shifts water from ocean to land, andit takes some time for this to runoff back into theoceans,” Willis noted. “This effect usually causes
about 1 centimetre of rise and fall each year, with a
bit more or less during El Niño and La Niña years. It’s
literally like the heartbeat of the planet.”
While a few millimetres of sea level rise per year may
seem small, scientists estimate that every 2.5 centimetresof sea level rise translates into 2.5 meters of beachfront
lost along the average coast. It also means that high tides
and storm surges can rise even higher, bringing morecoastal flooding, even on sunny days. In a report issued
in February 2022, U.S. scientists concluded that by 2050
sea level along U.S. coastlines could rise between 25 to
30 centimetres above today’s levels.
“What stands out from the satellite altimetry record isthat the rise over 30 years is about ten times bigger
than the natural exchange of water between ocean
and land in a year,” stated Willis. “In other words, thehuman-caused rise in global sea level is now ten times
bigger than the natural cycles.”Massive Algal Blooms in the Gulf of Finland
Copernicus image of the day
https://www.copernicus.eu/en/media/image-day

Credit: European Union, Copernicus Sentinel-2 imagery

Every summer, colourful algal blooms can be observed in
the shallow waters of the Baltic Sea. This image, acquiredby one of the Copernicus Sentinel-2 satellites on August
8, 2022, shows a massive algal bloom ongoing in thecentral-eastern part of the Baltic Sea, known as the Gulf
of Finland. This bloom was probably triggered by heatwaves in the area during June and July 2022. According toCopernicus Marine Environment Monitoring Service data,
the sea surface temperature anomaly at the time in thisarea was approximately +2ºC.
The resolution of the Copernicus Sentinel-2 satellites
allows Copernicus services to monitor marine biologicalactivity and water quality worldwide.

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32

River Rhine Runs Dry
European Space Agency

The River Rhine, near Cologne, in Auguet 2021
The River Rhine, near Cologne, in Auguet 2022
Images contains modified Copernicus Sentinel data (2021-22), processed by ESA, CC BY-SA 3.0 IGO

Water levels on the River Rhine, Europe’s secondlargest river, have continued to drop owing to soaring
temperatures and lack of rainfall, preventing many vessels
from navigating through the waters at full capacity. The
Copernicus Sentinel-2 mission captured part of the Rhine
near Cologne, showing the stark difference between
August 2021 and August 2022.

Water levels at the chokepoint of Kaub, near Frankfurt,
fell to 32 cm in depth on July 15, down from 42 cm froma week earlier. Ships, however, need around 1.5 metresto be able to sail fully loaded, making it difficult for larger
vessels to navigate through the waters. Freight ships
continue to sail, but only with around 25% to 35% of theircapacity.

Flowing from the Swiss Alps to the North Sea, the Rhine
is an important shipping route for many products fromgrains to chemicals to coal. When water levels drop, cargovessels need to sail with reduced loads, so they don’t run
aground.

These low water levels are emerging earlier than usual;the lowest annual water levels are typically recorded during
September or October. However, reduced temperaturesand predicted rainfall may offer relief to the Rhine.

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33

Drought Causes Yangtze to Shrink
European Space Agency

The Yangtze and Jialing rivers, near Chongqing
on August 15, 2021

The Yangtze and Jialing rivers, near Chongqing
on August 21, 2022

Images contains modified Copernicus Sentinel data (2020-22), processed by ESA, CC BY-SA 3.0 IGO

A record-breaking drought has caused
parts of the Yangtze River to dry up—
affecting hydropower, shipping routes,
limiting drinking water supplies andeven revealing previously submerged
Buddhist statues.
The Yangtze is China’s most important
river, providing water to more than
400 million people. This summer,
it has reached record low waterlevels, with rainfall in the Yangtze

basin around 45% lower than normal
with entire sections and dozens oftributaries drying up. The loss of waterflow to China’s extensive hydropowersystem has created problems in
Sichuan, which receives more than
80% of its energy from hydropower.
Images captured by the Copernicus
Sentinel-2 mission show a comparisonof the Yangtze and Jialing rivers, near
Chongqing between this year andwww.geo-web.org.uk

last. Higher than normal temperatures
increase the evapotranspiration of theriver waters and, together with missing
precipitation, result in lower waterlevels and sediment transportation
downstream. This explains thesignificant colour difference of the
Yangtze in the 21 August 2022
acquisition. Several areas of dry andexposed riverbed can also be seen
west of Chongqing.

34

Franz Josef Land
MODIS WEB Image of the Day

Image Credit: MODIS Land Rapid Response Team, NASA GSFC

Sitting at the northern-most tip of Russia andonly 970 kilometres away from the North Pole, thearchipelago known as Franz Josef Land remains
coated in ice year-round. With such a northerly
location, frigid temperatures are the norm. In
summer, the average high is just 2°C and it
plummets to about -22°C in winter. The steady freeze
helps to maintain the presence of glaciers, which
cover roughly 85% of the islands.
Despite the harsh climate, life finds a way toflourish. Vegetation includes lichens, mosses, andArctic flowering plants. Polar bears thrive on land,
while sea birds such as guillemots, kittiwakes, andlittle auks breed in abundance on the cliffs. Atlantic
walrus, bowhead whales, shark, seals, and eventiny copepods and phytoplankton live in the waters
around and between the islands.
Franz Josef Land was included in the Russian Arctic
National Park in 2016, due to its pristine natureand biodiversity. Given that the ice on and around
Franz Josef Land depends on frigid temperatures

year-round, and island life depends on ice, thenature of these islands is at particular risk in a
warming climate, despite preservation provided
by classification as a park. A study published inJune 2022 in the journal Scientific Reports found theNorthern Barents Sea to be an exceptional warming
hot-spot, with warming rates up to twice as high as
previously estimated. The study states:‘The regional warming rate for the Northern
Barents Sea region is exceptional and corresponds
to 2 to 2.5 times the Arctic warming averages and
5 to 7 times the global warming averages.’
On August 17, 2022, the Moderate Resolution
Imaging Spectroradiometer (MODIS) on board NASA’s
Aqua satellite acquired this true-colour image of thenorthern section of Franz Josef Land. The islands
remain covered with glaciers, but sea ice is scarcearound and between most of the islands. Scantice floats to the east of the islands while copious
broken ice covers the Barents Sea north the of thearchipelago.

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35

Lake Balkhash, Kazakhastan
NASA Earth Observatory
Caption by Adam Voiland

Lake Balkhash, imaged by the Copernicus Sentinel-2 mission on November 29, 2021.
Image contains modified Copernicus Sentinel data (2021), processed by ESA, CC BY-SA 3.0 IGO

Lake Balkhash, the largest lake
in Central Asia, is featured in thisfalse-colour image captured by theCopernicus Sentinel-2 mission.
The lake, which is situated in eastcentral Kazakhastan, is around 605
km in length from east to west, witha maximum depth of around 25 m.
The lake’s size varies depending
on water balance, with its areafluctuating between 15 000 and 19
000 square kilometres.
Jutting out into the lake is theSarymsek Peninsula which divides
Balkhash into two separate
hydraulic parts. The west part is
wide and shallow with its wateron this side particularly fresh andsuitable for drinking. The east part,on the other hand, is narrow andrelatively deep, with its waters on

this side of the basin brackish andsalty. The two parts of the lake
are united by a narrow strait, the
Uzynaral visible in the centre of theimage, with a depth of around 6 m.
The sediment plume passing
through the Uzynaral Strait ismost likely due to waves stirring
up sediments from the bottom of
the lake. This has led to a higher
reflection and thus a brighter water
colour in this part of the lake.
The north banks of Lake Balkhash
are high and rocky while the southbanks are low and sandy, with wide
belts covered with thickets of reeds
and numerous small lakes. These
low-lying banks are periodicallyflooded by the waters of the lake.

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A high presence of sea ice canbe seen in bright blue-greenish
colours especially near the southernshoreline. This colour is due to ice
having a higher reflectance in thevisible parts of the spectrum than in
the near-infrared. Balkhash usuallyremains frozen from the end of
November to the beginning of April,with this image captured on 29
November 2021.
South of Balkhash lies theSaryesik-Atyrau Desert, which
stretches for around 400 km ineast Kazakhastan. There are agreat number of small lakes, ponds
and wetlands in the desert (visible
in brown), as well as occasional
grasslands, that support a varied
animal and bird population.

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