Group for Earth Observation

No 81 - March 2024

The volcanic smoke plume from Iceland’s Reykjanes peninsula shows clearly as it drifts over the ocean
in this MODIS image from NASA’s Terra Earth Observation Satellite on February 8, this year.
Image: NASA Worldview Snapshots (https://wvs.earthdata.nasa.gov)

GEO MANAGEMENT TEAM

Useful User Groups

General Information

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

John Tellick,email: information@geo-web.org.uk

GEO Newsletter Editor

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

Les Hamilton,

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.

email: geoeditor@geo-web.org.uk

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

Webmaster and Website Matters

https://groups.io/g/SatSignal

Vacancy

MSG-1
This forum provides a dedicated area for sharing
information about hardware and software for receiving
and processing EUMETCast data.

e-mail: webmaster@geo-web.org.uk

Management TeamDavid Anderson

https://groups.io/g/MSG-1

Rob Denton
Nigel Evans: nigel.m0nde@gmail.com

GEO-Subscribers
This is the official group is for subscribers of the Groupfor Earth Observation (GEO), aimed at enthusiasts
wishing to exchange information relating to either GEO
or Earth Observation satellites.

Clive Finnis
Carol FinnisPeter GreenDavid Simmons

https://groups.io/g/GEO-Subscribers/

David Taylor

Copy for the Newsletter

GEO Quarterly Back-issue Archive

The Editor is always delighted to receive material for
inclusion in the GEO Quarterly Newsletter. These canrelate to any aspect of Earth Imaging, especially• Technical articles concerning relevant hardware andsoftware• Construction projects• Weather satellite images• Reports on weather phenomena• Descriptions of readers’ satellite imaging stations• Activities from overseas readers• Letters to the Editor• Problems and Queries for our experts to answer

GEO Quarterly has been in continuous publication since2004, and all previous issues are available on-line as
PDF copies from:https://leshamilton.co.uk/GEO/archive.htm

Contributions should of course be original and besubmitted to the editor by e-mail not later than the
middle of the month preceding publication.
If your article submission contains embedded images
and diagrams, please note that you must also submit
copies of the original images as separate attachments:
these are essential for page make-up purposes.
Materials for publication should be sent to the editor,
Les Hamilton, at

There is also a searchable index to all titles fromprevious years, and this can be downloaded from:https://leshamilton.co.uk/soft/geoindex-setup.exe

geoeditor@geo-web.org.uk

www.geo-web.org.uk

2

Les Hamilton

The remarkable image on the front cover of this issue was captured by NASA’s Terrasatellite just a few hours after an early morning eruption from Iceland’s Reykjanes Volcano
on February 8, 2024, and shows a plume of gas and dust sweeping southward over the
Atlantic Ocean. You can read about this eruption in the article on page 19.
As you read this issue of GEO Quarterly, it is anticipated that—if all goes to plan—a new
Russian meteorological satellite, Meteor M No 2-4, should already be in orbit: launch,from Vostochny Cosmodrome, was scheduled for 05.43 UT on February 29. You can readongoing information about this new craft at:https://usradioguy.com/satellites/meteor-m-2-4-launch/
The current Meteor M No 2-3 commenced image transmissions within 24 hours of launch,so it is already worth looking out for it, most probably transmitting on the 137.10 MHz
frequency.
Disappointingly, the launches of Meteor M No 2-5 and Meteor M No 2-6, previously expectedto launch in 2024 and 2025 respectively, are reported now to be delayed for at least one
year.

Contents
Snow in Scotland
MODIS Web Image of the Day
Erebus Breaks ThroughNASA Earth Observatory
Unrest at Anak Krakatau
NASA Earth Observatory
Egypt’s Toshka Lakes
MODIS Web Image of the Day
Yukon Delta
European Space Agency
Auroras Light up the North
NASA Earth Observatory
A Lake Born out of an Earthquake
NASA Earth Observatory
Tropical Cyclone Jasper Brings Heavy Rainfall To Queensland David Sale
Water in South Australia’s Salt Lakes
MODIS Web Image of the Day
Iceberg A23a at the Tip of the Antarctic Peninsula
MODIS Web Image of the Day
Quelccaya Ice Cap Then and Now
NASA Earth Observatory
Iceberg on the Loose
European Space Agency
Third Reykjanes Volcanic Eruption in IcelandNASA Earth Observatory
The changing Face of Cadman Ice Shelf
European Space Agency
Retreat at Klinaklini
NASA Earth Observatory
Worrying lack of snow in the Pyrenees
Copernicus Image of the Day
The Lovely Shape of Spirit Lake
NASA Earth Observatory
Cloud Vortices over the Atlantic
MODIS Image of the Day
Cyclone Belal hits La Reunion and Mauritius
Copernicus Image of the Day
The Zahara-El Gastor Water Reservoir at Critical Level
Copernicus Image of the Day
Badwater Basin Refills
NASA Earth Observatory
Volcanic Activity at the Pococatepetl Volcano
Copernicus Image of the Day
A Rare Tropical Storm in the South Atlantic
NASA Earth Observatory
Winter on the Tibetan Plateau
MODIS Web Image of the Day
Satellite Status		

www.geo-web.org.uk

5
6
7
8
9
10
11
12
15
16
17
18
19
21
23
25
26
27
28
29
30
32
33
34
35

3

Clear Skies over Scotland on December 26, 2023 reveled sparkling new snowfall over the Highlands, as
portreyed by the MODIS instrument aboard NASA’s Terra Earth Observation Satellite
Image: NASA Worldview Snapshots (https://wvs.earthdata.nasa.gov)

www.geo-web.org.uk

4

Snow in Scotland
MODIS Web Image of the Day

Skies were clear over Scotland on December 26,
2023, allowing the Moderate Resolution Imaging
Spectroradiometer to capture a false-colour image ofsnow blanketing the Scottish Highlands. This typeof image combines both infrared and visible light(MODIS bands 7,2,1) to help separate snow (electricblue) from vegetation (bright green) and water (darkblue). Clouds usually appear white, although highcloud that contains ice may be tinted with lightelectric blue.
Despite warm weather and rain in the lowlands
the previous day, fresh snowfall over the Highlands
prompted the Met Office to officially declare a
White Christmas in Scotland. Several ski resorts
reported light snow between December 25 and 26,
with the highest amounts (4 cm) at both Lecht andCairngorm. Meanwhile, the Met Office recorded
a high temperature of 13.6°C at Exeter Airport,

England, making it the warmest December 25 in thatlocation since 2016.
By December 27, the clear skies had clouded
over as Storm Gerrit began to pound the United
Kingdom. The Met Office ordered yellow warnings
for rain, wind, and snow across much of Scotland,with warnings remaining in effect in Shetland until
December 28. The Scottish Environment Protection
Agency (SEPA) issued flood alerts and warnings
across the country as high wind roared and heavy
precipitation fell across the region. Train services
and ferries were cancelled, and widespread power
outages were reported across Scotland. Hundredsof cars and other vehicles were stuck on a the A9,
due to heavy snow, many drivers being trappeed intheir vehicles for as long as eight hours before winterweather response teams managed to reopen the roadlate in the dqy.

Image Credit: MODIS Land Rapid Response Team, NASA GSFC

www.geo-web.org.uk

55

Erebus Breaks ThroughNASA Earth Observatory
Story by Lindsey Doermann

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

The summit crater of Mount Erebus, the world’s
southernmost active volcano, appeared above theclouds on a late-spring day in 2023. The OLI-2(Operational Land Imager-2) on Landsat 9 captured
this view of the stratovolcano on November 25.
Mount Erebus is one of several volcanoes forming
Ross Island off the coast of West Antarctica.
At 3,794 metres above sea level, it looms over
McMurdo Station, located just 35 kilometresaway. These volcanoes occur in a rift zone where
extension has caused the crust to thin and allowedmagma to migrate up through faults to the surface.
In this detailed view, the Landsat image includes
the shortwave infrared signal (red) produced byheat from a lava lake in the summit crater. The

lake has been active since at least 1972 and is
one of only a few long-lived lava lakes on Earth. It
constantly churns and occasionally spews bombsof molten rock in Strombolian eruptions. Geologists
want to learn why an active lava lake has persisted
here for so long. Recent research suggests one
reason could be the magma’s low water content,
which makes it less volatile as it approaches thesurface.
Erebus was active prior to the emergence of thislava lake, including in 1841 when British Royal
Navy officer James Clark Ross first sighted it
during his Antarctic exploration. Mount Erebus
and neighbouring Mount Terror were named after
warships retrofitted for use in that expedition andnumerous other polar voyages.

www.geo-web.org.uk

6

Unrest at Anak Krakatau
NASA Eart5h Observatory
Story by Adam Voiland

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

Anak Krakatau is a small,
unimposing volcanic island
between the Indonesian islandsof Java and Sumatra. However,its frequent blasts and explosions
serve as a reminder of its mighty,
and occasionally menacing, power.
The Operational Land Imager (OLI)
on Landsat 8 captured this imageof a volcanic plume drifting fromthe volcano on December 2, 2023.
It includes an infrared signal (red)that was produced by the heat ofmolten rock in the crater near theisland’s summit.
Geologists have tallied 57 eruptive
periods from this location since
the beginning of the Holocene,roughly 11,700 years ago. The
most recent eruptive period,
which started in May 2021

and continued into December
2023, has featured frequent
but generally mild Strombolian
blasts of volcanic gases and ash
particles. Materials ejected fromthe volcano’s vent are typicallylofted a few hundred metresabove the summit, and small lava
flows occasionally drain down theisland’s flanks and into the sea.
Beginning on November 26, 2023,
geologists with the Indonesian Centre
for Volcanology and Geological Hazard
Mitigation began to report more
intense explosions, with plumesof volcanic material rising up to
1,000 metres above the vent. Given
the heightened unrest, the center
warned the public to stay at least
five kilometres from the crater.
The Volcanic Ash Advisory Center
in Darwin, Australia, also issued

www.geo-web.org.uk

multiple warnings to the aviation
community of elevated risks of ash
in the area.
The volcano is infamous for
producing an explosive eruption
and powerful tsunami in 1883
that proved to be one of thedeadliest and most destructive
volcanic events in modern history.
The blast obliterated the islandof Krakatau, but fifty years latera new island—Anak Krakatau(meaning ‘child of Krakatau’ inIndonesian)—emerged from thesea. As recently as December
2018, hundreds of people diedand thousands were injured on
Java and Sumatra after part ofAnak Krakatau’s southwestern
flank collapsed and produced
a tsunami after a particularly
powerful eruption.

7

Egypt’s Toshka Lakes
MODIS Web Image of the Day

The Toshka Lakes on December 6, 2019

The Toshka Lakes on December 6, 2023

Image Credit: MODIS Land Rapid Response Team, NASA GSFC

Egypt’s Toshka Lakes sit in natural depressions found in the vast, arid sands of the Sahara
Desert. They were created in the 1980s and 1990s through diversion of water from Lake
Nasser, the massive 550 kilometre long reservoir built on the Nile River between 1958 and1970. As the depressions became flooded, four major lakes appeared amongst the desert
sands.
Since they were created, these lakes have been dependent on overflow from Lake Nasser,with water levels rising in years of heavy rain and shrinking in years of drought. The
Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired
two true-colour images, one on December 6, 2023, and another on December 6, 2019, that
illustrate wide fluctuations in the Toshka Lakes.
In early 2019, lack of rainfall had nearly dried up the Toshka Lakes, leaving parched marksin the sand where they had once glittered with blue water. Abundant summer rainfall,especially in Sudan and South Sudan began to fall in that same year. The heavy rain filled
the Nile which, in turn, raised water levels in Lake Nasser. Outflow from Lake Nasser began
to regenerate the eastern portion of the Toshka lakes. This was the situation on December
6, 2019, and the image shows the newly-filled eastern lake while the others remainparched.
Beginning in 2020, record-breaking floods drenched Sudan, raising the water level in Lake
Nasser to a record high. Flooding has occurred in Sudan and South Sudan every summer
since 2019, resulting in serious difficulties for agriculture, livestock, and people living in theregion, as well as increasing the overflow from Lake Nasser that feeds the Toshka Lakes.
The water level in Lake Nasser reached another record high following the 2022 floods.
In 2023, floods began in September, initially destroying thousands of houses and damaging
hundreds more. Additional flooding in late October caused the displacement of more than
1,000 people and killed at least ten people, according to ReliefWeb.
The image acquired on December 6, 2023, shows the impact of these multiple years offlooding on the Toshka Lakes. Not only are the original four lakes completely full, but new,smaller lakes have formed by filling depressions around them. Irrigated agricultural fields
are visible between Lake Nasser (lower right) and the Toshka Lakes.

www.geo-web.org.uk

8

Yukon Delta
European Space Agency

Image contains modified Copernicus Sentinel 2 data (2017), processed by ESA, CC BY-SA 3.0 IGO

The Yukon River rises in British Columbia in
Canada and flows through Yukon Territory before
entering Alaska and finally draining into the Bering
Sea. This image, recorded on 29 August 2017,shows how the river branches off into numerous
channels that meander through the low-lying
terrain on their way to the sea. The sandy colour ofthese channels and of the coastal water illustrates
how much sediment the river was carrying to thesea at that time of year.
It is estimated that 95% of all sediment transported
during an average year occurs between May
and September. During the other seven months,
concentrations of sediment and other waterquality constituents are low. However, scientists
also believe that sediment flow has increased

over the last few decades because permafrost isthawing in the Yukon River Basin and ice breakup
occurs earlier in the year owing to warmer air
temperatures. This is important because elevatedconcentrations can adversely affect aquatic life by
obstructing fish gills, covering fish spawning sites,
and altering habitat of bottom-dwelling organisms.
Metals and organic contaminants also tend toabsorb on to fine-grained sediment.
The Copernicus Sentinel-2 satellites each carry ahigh-resolution camera that images Earth’s surface
in 13 spectral bands. While the mission is mostly
used to track changes in the way land is being
used and to monitor the health of our vegetation,it also provides information on the condition ofcoastal waters.

www.geo-web.org.uk

9Auroras Light Up the North
NASA Earth Observatory
Story by Lindsey Doermann

NASA Earth Observatory image by Lauren Dauphin, using VIIRS day-night band data from the Suomi National Polar-orbiting PartnershipA flurry of solar activity in mid-December 2023 sentenergized particles crashing into Earth’s magnetosphere,
producing undulating auroras across northern latitudes ofour planet. The VIIRS (Visible Infrared Imaging Radiometer
Suite) on the NOAA-NASA Suomi NPP satellite captured thisimage of light from the aurora over western Canada in theearly morning of December 17, 2023. The day-night bandof VIIRS detects nighttime light in a range of wavelengths
from green to near-infrared and uses filtering techniques
to observe signals such as city lights, reflected moonlight,
and auroras.

magnetic field. Interactions between these expulsions fromthe Sun and the upper atmosphere of Earth produce lightthat makes up colorful aurora displays.

These auroras may have stemmed from several
coronal mass ejections that were observed on
December 14 and 15. Minor to moderate geomagnetic
storm conditions were expected in the following days,
according to NOAA’s Space Weather Prediction Center.
Coronal mass ejections contain large amounts of plasma
from the Sun’s corona and carry with them an embedded

The aurora seen here occurred several days after thestrongest solar flare of this solar cycle so far. Whereas
coronal mass ejections may take several days to travel toEarth, solar flares reach the planet in a matter of minutes
and interfere with radio communications. Coronal massejections often, but not always, occur in tandem with solar
flares.

The Sun’s activity is ramping up as it approaches the peakof solar cycle 25, forecast to occur in or around July 2025.
The Sun’s magnetic field flips at the peak of these cycles,
each of which lasts approximately 11 years. Scientists
track fluctuations in solar activity in part by monitoring thenumber and location of sunspots—dark blotches on the
Sun’s surface that are the main source of solar eruptions.

www.geo-web.org.uk

1010

A Lake Born out of an Earthquake
NASA Earth Observatory
Story by Lindsey Doermann

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

At their most deadly and destructive, earthquakes cantopple buildings, crumple roads, and trigger tsunamis.
They can also fundamentally reshape the landscape,reroute rivers, and even form new lakes.
The latter took place in the northwest corner of Tennesseein the early 19th century. Between December 1811 andFebruary 1812, three earthquakes with magnitudes
greater than 7 occurred in the New Madrid seismic zone,
which encompasses southeastern Missouri, northeastern
Arkansas, and neighboring parts of Tennessee andKentucky. The last of these quakes, on February 7, 1812,
centered near New Madrid, Missouri, was especiallynotable: It temporarily rerouted the Mississippi River,permanently dammed the Reelfoot River, and directedwater to fill in a low-lying area to form Reelfoot Lake.
More than two centuries later, Reelfoot Lake remains apersistent feature on the Tennessee landscape. The OLI-2(Operational Land Imager-2) on Landsat 9 captured thisimage of the lake, surrounding wetlands, and the nearby
Mississippi River on November 27, 2023.
Rivers that run over fault lines are susceptible to being
stopped abruptly and wrenched askew when the groundshifts. Earthquake-induced river avulsions (suddenchanges of course) have been documented throughout
history. In 2016, for example, the Kaikoura earthquake in
New Zealand effectively dammed the Waiau Toa (ClarenceRiver) and forced it into an entirely new channel.

In the case of the earthquake that formed Reelfoot Lake,lore has it that the shaking even made the Mississippi
flow in reverse for a time. However, that may have been
an illusion caused by earthquake-generated water waves
travelling upriver. The shaking virtually destroyed thesmall Missouri town of New Madrid. Eyewitnesses near
the epicenter also described trees being uprooted and theground rising, falling, and cracking open. People in distantcities such as Boston, Detroit, and New Orleans reported
having felt the shaking.
Some geologists consider the New Madrid seismic zone
the most hazardous earthquake region east of the Rocky
Mountains. Yet its history of large quakes and risk of
future destructive activity remain sources of inquiry anddebate. Geologists understand less about what causes
earthquakes in the middle of tectonic plates than they doabout ones at plate boundaries. What they do know is thatseismic waves in the eastern U.S. travel much farther thanthey do in the west, so tremors of the same magnitudeaffect a larger area.
The Reelfoot Lake of today is a haven for boating, fishing,
and watching wildlife. Bald cypress (Taxodium distichum)trees grow in marshy areas, while stumps from pre-flood
forests are submerged in the water. The lake is surrounded
by wetlands that comprise a state park and national wildlife
refuge. Bald eagles and waterfowl overwinter in the area,
while songbirds, frogs, and other aquatic life abound in thespring and summer.

www.geo-web.org.uk

11Tropical Cyclone Jasper Brings Heavy Rainfall To Queensland
David Sale

Cyclone Jasper was the first
cyclone in the Australian‘area of responsibility’ for the2023-2024 cyclone season.
Category 1 was first assigned on
December 5, 2023 when it wasnear the Solomon Islands and threedays later it had strengthened tocategory 4 with wind speeds of
up to 220 kilometres per hour.
Fortunately, it had moved well into
the Coral Sea by this time.
Jasper slowly dissipated as it
approached the Queensland
coast of Australia as a slow
moving category 2 cyclone, soonafter downgraded to category 1.
Unfortunately, Jasper made landfall
on December 13 and stalled over
the Cape York Peninsula where its
cyclonic circulation brought warm,
moist northeasterly winds fromthe Coral Sea onshore, resulting inheavy precipitation along the coast
for several days.
Notwithstanding the storm’s
downgrade, this resulted inconsiderable precipitation, withsome areas recording in excess
of 400 millimetres in a 24 hour
period. The highest incidence was
Mossman’s 714 millimetres—arecord 24 hour total foranywhere in Australia. Andin many locations more than
1000 millimetres fell during afive day period, with Whyanbeel
Valley recording 1934 millimetres.
Indeed, the Australian Bureauof Meteorology reported thatsome isolated locations near Port
Douglas and Cairns saw evengreater amounts, in excess of2000 millimetres.
Predictably, there were adverse
consequences with extensive
flooding in some areas. At one
point, 40,000 people were without
power. There was also a severe
impact to the fruit growing industry(mangoes, papaya, banana,
avocados) with a large amount offruit lost just as it was ripening,and damage to the trees.

This Himawari Band-3 visible image of Cyclone Jasper was received
as it approached Queensland on December 11, 2023
Credit: Himawaricast

Track plot of Cyclone Jasper (green=category 1, yellow=C2, orange=C3, red=C4)
Credit: Zoom Earth (https://zoom.earth/)www.geo-web.org.uk

12

On 17 January 2024, the Copernicus Sentinel-2 mission captured this image of a lava flow in Iceland’s Reykjanes
Peninsula. The lava had reached the town of Grindavik, which had been previously evacuated. According to the Icelandic
Met Office, on the same day, magma accumulation was continuing under the region with a likelihood that new eruptive
fissures might open without warning.
Image contains modified Copernicus Sentinel data (2024), processed by ESA, CC BY-SA 3.0 IGO

www.geo-web.org.uk

13

This stunningly beautiful image, captured in Aberdeen from Meteor M2-3 on the morning ofJanuary 17 this year, shows northern Scotland, covered deep in snow following two days of blizzards.

www.geo-web.org.uk

14

Water in South Australia’s Salt Lakes
MODIS Web Image of the Week

Lakes Torrens and Gairdner on December 14, 2003

Lakes Torrens and Gairdner on December 4, 2003

Image Credit: MODIS Land Rapid Response Team, NASA GSFC

As forecasters warned of a ‘hot and stormy’ week acrossSouth Australia, a strong trough of low pressure dropped
a deluge on a normally arid part of the state between
December 6 and 13, 2023.
According to the Weekly Australian Climate, Water andAgricultural Update published on December 14, rainfall
totals of up to 150 millimetres were recorded across South
Australia during that week. South Australia is the driestof the Australian states, with less than half of it receiving
more than 400 millimetres of rainfall in an entire year.
Lake Torrens and Lake Gairdner are located in some of themost arid land of South Australia, a region that receives anannual rainfall of only about 210 millimetres. Under typicalconditions both lakes spend most of their days as large,
dry salt pans. However, because they are so shallow,
with depths of no greater than one metre, when strong
rains fall, Lake Torrens and Lake Gairdner can rapidly fillwith water. The December storms dropped enough rain toconvert these salt pans into spectacular water-filled lakes.
The Moderate Resolution Imaging Spectroradiometer(MODIS) on board NASA’s Aqua satellite acquired a falsecolour image of freshly-filled Lake Torrens (east) and lake
Gairdner (west) on December 14. This type of image uses
both visible and infrared light (bands 1, 2 and 7) to help
visualise specific features, such as separating deeper
water (dark blue) from salt (bright blue) and moist salt
(teal). Here, arid or sparsely vegetated land looks tan,
while vegetation is green.
A second false-colour image of the same area wascaptured by Aqua MODIS on December 4, prior to thetorrential rains. This image shows the lakes filled withsalt, most of which appears quite dry (lightest blue). The
deep waters of Spencer Gulf are seen in the lower right(southeast) section image and appear dark blue.

www.geo-web.org.uk

15

Iceberg A23a at the Tip of the Antarctic Peninsula
MODIS Web Image of the Day

Image Credit: MODIS Land Rapid Response Team, NASA GSFC

On November 27, 2023, a break in the swirling
cloud cover allowed a glimpse of the Earth’s
largest iceberg drifting past the tip of the Antarctic
Peninsula. The Moderate Resolution Imaging
Spectroradiometer (MODIS) on NASA’s Terrasatellite acquired this true-colour image of Iceberg
A23a northeast of the Joinville Island group,
which are the northernmost-group of islands on
the Antarctic Peninsula, on that same day.
The massive iceberg calved from the Filchner
Ice Shelf in 1986 but didn’t drift far before it
grounded in the Weddell Sea—and was stuck
there for decades. Very slowly the massive iceberg

lost a bit of mass here and there, until its longkeel was finally able to loosen from the muddy
bottom of the Weddell Sea and begin to drift.
Scientists first spotted tiny movements in A23a’s
position in 2020, but only recently has it beencaught by currents and started to drift quickly
eastward towards the relatively warm waters of
the South Atlantic Ocean.
A23a is estimated to measure about 400 meters
thick and span an area of about 4,000 square
kilometres. That’s more than twice the area ofGreater London, which covers 1,572 square
kilometres.

www.geo-web.org.uk

16
16

Quelccaya Ice Cap Then and Now
NASA Earth Observatory
Story by Kathryn Hansen

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

The Quelccaya Ice Cap rests on a high-altitude
plateau of the Andes Mountains in Peru. But
like other tropical glaciers across the planet, thecomparatively cold temperatures found at highaltitudes are not enough to protect it from the gripof climate change.
This image pair shows the retreat of Quelccaya’s
ice edge between September 3, 1988 (left), andOctober 22, 2023 (right). They were acquired with
the TM (Thematic Mapper) on Landsat 5 and the
OLI (Operational Land Imager) on Landsat 8,
respectively. Christopher Shuman, a University of
Maryland, Baltimore County, glaciologist based atNASA’s Goddard Space Flight Center, estimatesthat the ice area in 1988 spanned about 58 square
kilometers: by 2023, it spanned just over 40 square
kilometers.
Notice the accrual of meltwater lakes in the later
image, particularly along the ice cap’s western side.
Many of these lake basins, carved by moving ice,have lost contact with the ice that formed them.
The ice cap also feeds the Vilcanota River and Lake
Sibinacocha (west of this image) and has long been
an important water source for people living nearby
and downstream.
Some of the lakes have already come and gone
during the span of these images, including one
that in November 2022 produced a glacial lake
outburst flood (GLOF). Shuman detected the event
in Landsat images showing the emptying of a lakeon the ice cap’s eastern side and a long path where
the rushing floodwater had scoured the vegetation.
The flood scar is still visible in this 2023 image.

Before Landsat satellites revealed the decadalchanges, scientists already knew the ice cap was
shrinking. Since 1974, Lonnie Thompson andcolleagues from Ohio State University have been
mounting expeditions to study Quelccaya up close.
‘Both ground-based and satellite images allow the
documentation of the rates of glacier retreat, which
now average about 14 meters per year,’ Thompson
said. Thompson’s team has shared Landsat images
documenting the ice cap’s retreat with local officials
and indigenous people living near the ice cap.
As the planet’s tropical glaciers are being lost,
so are the temperature and climate records longpreserved in their ice. Thompson’s team has drilled
ice cores from many tropical glaciers, including
Quelccaya. By analyzing the layers in these cores,
scientists can get a near-annual record of air
temperatures and atmospheric composition datingback 1,800 years.
‘Tropical glaciers might represent our only
opportunity to capture global mean temperaturechanges through time, as well as how climate andthe environment have changed in an area that
represents 50 percent of the surface area of ourplanet and where over 50 percent of our 8 billion
people live,’ stated Thompson.
At Quelccaya, that record could be gone by the endof the 21st century—the expected timeframe for theice cap’s demise. ‘The only proof of its existence willbe the land-based and satellite images of what wasonce a magnificent ice cap located directly above theAmazon Basin.’www.geo-web.org.uk

17

Iceberg the loose
European Space Agency

After being grounded on
the ocean floor for well overfour decades, the largest
iceberg in the world is on
the loose.
The iceberg, known as
A23a, calved from theFilchner-Ronne ice shelfin West Antarctica in 1986
but quickly ran aground.
By 2020, it had lost its gripon the sea floor and begun
drifting in the Weddell Sea.
Scientists say that it is not
unusual for icebergs to
become grounded, but overtime they shrink enough tounground and float.

Iceberg A23a imaged on November 2, 2023

Now, however, driven bywinds and currents, A23a
has put a spurt on andis heading quickly awayfrom Antarctic waters—asthese images of Copernicus
Sentinel-1 images show.
The satellite images wereacquired on November
2, November 14 andNovember 26, 2023.
Like most icebergs fromthe Weddell sector, A23a
is likely to end up in theSouth Atlantic on a pathcalled iceberg alley.

Iceberg A23a imaged on November 14, 2023

Covering around 4000
square kilometres—more
than four times the size of
New York city—and around
400 metres thick, A23a iscurrently the world’s biggest
iceberg.
These Copernicus
Sentinel-1 images also
illustrate how the iceberg
has rotated as it travelled
between November 2 andNovember 26, 2023.

Images contain modified Copernicus
Sentinel data (2023), processed by
ESA, CC BY-SA 3.0 IGO

Iceberg A23a imaged on November 26, 2023

www.geo-web.org.uk

18

Third Reykjanes Volcanic Eruption in IcelandNASA Earth Observatory
Story by Adam Voiland

Figure 1 - Landsat-9 image showing details of the Reykjanes eruption
NASA Earth Observatory image by Lauren Dauphin, using data from GIBS/Worldview

After a lull in activity, fresh lava has once again poured
from the Reykjanes peninsula in southwestern Iceland.
This latest eruption—the third in the region since
December 2023—began early on February 8, 2024, withlava spraying up to heights of 80 metres along a threekilometre long fissure near Mount Sýlingarfell. This small
peak is north of the fishing village Grindavík and east of
the Svartsengi power station and Blue Lagoon geothermal
spa.
Figure 1 was acquired on February 10, 2024, by the OLI-2(Operational Land Imager-2) on Landsat 9. Infrared andvisible observations (bands 7-6-3) have been overlain on anatural-colour image to help distinguish the heat signatureof the lava. Still recent but cooler lava, expelled near
Grindavík in January, appears black.

The topography around the fissure means that much of the
fresh lava flowed east into unpopulated areas rather than
to the south toward Grindavík. Some lava also flowed west
into the vicinity of the power plant and spa.
Earthen defensive walls protected both facilities, thoughlava did burn through a key hot water pipeline and tworoads. According to the Icelandic National Broadcasting
Service RÚV, authorities were in the process of restoring
hot water to homes in the area after conducting repairs on
the pipeline.
About seven hours after the eruption began, the MODIS(Moderate Resolution Imaging Spectroradiometer) on
NASA’s Terra satellite captured an image (figure 2)
showing a plume of gas and ash streaming to thewww.geo-web.org.uk

19

Figure 2 - Landsat-9 image showing details of the Reykjanes eruption plumeNASA Earth Observatory image by Lauren Dauphin, using MODIS data from NASA EOSDIS LANCE

southwest. This eruption was effusive—not explosive
like the Eyjafjallajökull eruption in 2010—and the plumecontained minimal ash, so did not cause any disruptions toeither domestic or international flights.

February 9, the Icelandic Met Office reported that seismic
sensors had stopped detecting volcanic tremors and thata recent drone flight showed no activity over the eruption
site—signs that the latest eruption was ending.

Volcanic plumes like the one shown here typically containwater vapour, sulphur dioxide, carbon dioxide and small
amounts of other volcanic gases. Researchers fromthe Icelandic Met Office and the University of Iceland
have noted that, at times, magma has interacted withgroundwater, adding to the amount of water vapour in theplume. After the initial burst of activity on February 8, theintensity of the eruption quickly faded, and in an update on

However, on February 12, the agency reported that theland surface above an underground magma reservoir near
Svartsengi had again begun to swell by between 0.5 and 1
centimetres per day, a rate similar to what was observed
prior to other recent eruptions. “It is therefore highly likelythat the cycle will continue in a few weeks with anotherdyke propagation and a volcanic eruption,” the agency
stated.

www.geo-web.org.uk

20

The changing face of Cadman Ice Shelf
European Space Agency

Using satellite data, scientists have discovered that theice shelf extending into the ocean from Cadman Glacieron the west Antarctic Peninsula collapsed leaving theglacier exposed to unusually warm ocean water, whichcaused the glacier to accelerate and retreat rapidly.
The research, published in Nature Communications,describes how a team of scientists, from the Universityof Leeds, Lancaster University, ENVEO, the Universityof Delaware and the British Antarctic Survey, used datafrom nine different satellite missions, including ESA’s

CryoSat and Europe’s Copernicus Sentinel-1, alongwith in-situ measurements to map how the floating ice
shelf and glacier changed.
They found that between November 2018 and May
2021, the glacier retreated a whopping eight kilometres,
after being stable for around 50 years. They concluded
that unusually high ocean water temperatures aroundthe west Antarctic Peninsula during 2018–2019 hadtriggered the Cadman Glacier system to change
dramatically.
Article continues overleaf ...

These side-by-side images use acquisitions from the Copernicus Sentinel-2 mission to show how the ice
shelf changed between 28 February 2017, at left and 19 November 2023 on the right.
Images contains modified Copernicus Sentinel data (2023), processed by ESA, CC BY-SA 3.0 IGO

www.geo-web.org.uk

21

Benjamin Wallis, from the University of Leeds who led theresearch, explained:‘By tracking Cadman Glacier with satellites we sawthat it started speeding up massively in 2018, andwhen we investigated ocean reanalysis data, we foundthat the waters nearby were up to 2°C warmer than
average at that time. We think the warmer waters
gradually started to eat away ‘at the Cadman Ice Shelf
from the early 2000s, but possibly from as early as the
1970s. The warmer water was not only on the surfaceof the ocean, but also deep in the water column. Thiswarmer water may have reached to where the shelf
was grounded on the sea floor. The result being thatthe ice shelf was melting from the bottom up, which wewere able to observe using satellite data.’
Extending from glaciers on land, ice shelves float on
the ocean surface and sometimes reach the ocean floor
where then can be anchored, or grounded. Importantly, ice
shelves act as a buttress, slowing the flow of the glacier
towards the sea.
The Cadman Ice Shelf had become so thin that it was
no longer able to hold back the glacier. In 2019, the shelf
broke free from the grounding zone, in effect slipping
anchor and enabling the Cadman Glacier to speed
up and drain more ice into the sea. According to thisnew research, the Cadman Glacier is now in a state of‘substantial dynamic imbalance’.

The researchers say that what has happened to theCadman Glacier can be seen as an example of a‘glaciological tipping point’, where a system in a steadystate can take one or two paths based on a change in anenvironmental parameter.
Such a tipping point was reached in 2018, resulting fromthe arrival of unusually warm ocean water which caused
the ice shelf to unground. Reaching this tipping pointcaused Cadman Glacier to increase its ice discharge by
28% in 13 months.
Prof. Michael Meredith, from the British Antarctic Survey
and one of the authors of the paper, stated:‘We have known for some time that the ocean around
Antarctica is heating up rapidly, and that this posesa significant threat to glaciers and the ice sheet, withconsequences for sea-level rise globally. What thisnew research shows is that apparently stable glaciers
can switch very rapidly, becoming unstable almost
without warning, and then thinning and retreating verystrongly.
‘This emphasises the need for a comprehensive ocean
observing network around Antarctica, especially inregions close to glaciers that are especially hard to
make measurements.’
ESA’s Mark Drinkwater added:‘Again we see that the Antarctic is more susceptible
to change than we thought a few years ago. It isimperative that we continue to monitor this fragile
continent and surrounding oceans. We can only
capture the full extent of such changes with panAntarctic measurements obtained by satellites overdecades.
‘Thankfully, we have missions such as CryoSat andCopernicus Sentinel-1 in orbit, but, importantly, weare developing new satellite missions such as theCopernicus Sentinel Expansion Mission Cristal and
Sentinel-1 Next Generation to continue, to sustain,and enhance these types of measurements in the
future.’The marine terminus: where the Cadman reaches the sea

The ice on the glacier has continued to thin, losing
20 metres a year, equivalent to a loss in height of a fivestorey building annually. And around 2.16 billion tonnes of
ice are draining from the Cadman Glacier into the ocean
each year.
‘Curiously, neighbouring glaciers on this part of thewest Antarctic Peninsula did not react in the sameway, which may hold important lessons for the way wecan better project how climate change will continue toaffect this important and sensitive polar region,’ noted
Benjamin Wallis.

With a launch plannedin 2027, the Copernicus
Polar Ice and Snow
Topography Altimeter,
CRISTAL, mission
will carry, for the firsttime, a dual-frequency
radar altimeter, andmicrowave radiometer,that will measureand monitor sea-ice
thickness, overlying
snow depth and iceArtistic impression of the Crystal craft
Image:ESA
sheet elevations.

www.geo-web.org.uk

22

Retreat at Klinaklini
NASA Earth Observatory
Story by Adam Voiland

Decades of satellite images ofwestern Canada make it clear thatthe region’s glaciers are shrinking andthat the rate of ice loss is accelerating.
In 1984, there were 14,329 glaciersin British Columbia and Alberta thatwere large enough to detect withsensors on the Landsat 5 satellite.
By 2020, nearly 8% of them—1,141
glaciers—had shrunk so much thatnewer Landsat sensors could nolonger distinguish them, according
to research conducted by Universityof Northern British Columbia
glaciologists Alexandre Bevington and
Brian Menounos.
‘Clean’ glaciers—those without muchdebris on them—went from losing an
average of 49 square kilometres (km2)
per year between 1984 and 2010
to 340 km2 per year between 2011
and 2020. In the same periods, thearea spanned by water pooling at theends of glaciers ballooned from about
9 km2 to 49 km2.

The Klinaklini Glacier in 1984
NASA Earth Observatory images by Wanmei Liang, using
Landsat data from the U.S. Geological Survey

The Klinaklini Glacier, the largest
glacier in western North America
outside of Alaska, is part of thisshrinking trend. The Coast Range
glacier, found in the south of British
Columbia, flows southward fromthe flanks of the 2864 metre Mount
Silverthrone and 2658 metre Mount
Somolenko into a forested valley
roughly 300 metres above sea level.
The pair of images above shows
how much Klinaklini has changed
between September 26, 1984 (upper),and September 22, 2023 (lower).
During this period, the glacier’s
terminus—sometimes called the snout
or toe—retreated northward by morethan five kilometres. In 1984, justa small glacial lake was present at
the terminus. By 2023, the lake hadgrown to five kilometres long and
two kilometres wide. It is now large
and deep enough that icebergs float
freely in it. The photograph at the
top of page 23, which was taken by
Menounos from a helicopter, is anview of the glacier as it appeared on
September 1, 2017.

The Klinaklini Glacier in 2023
NASA Earth Observatory images by Wanmei Liang, using
Landsat data from the U.S. Geological Survey

Klinaklini is also getting skinnier.
Analysis of digital elevation modelsof the glacier derived from images
acquired by the ASTER (Advanced
Spaceborne Thermal Emission and
Reflection Radiometer) on NASA’s
Terra satellite shows that Klinaklini’s
main stem thinned by nearly
200 metres between 2000 and 2019.

www.geo-web.org.uk

The meltwater that drains from theglacier flows first into the remote
Klinaklini River, then into Knight Inlet
and the Queen Charlotte Strait, before
eventually debouching into the Pacific
Ocean. The contribution of this one
glacier to sea level rise is tiny, but
the collective impact of the world’s
glaciers is important.

23

This photograph, taken from the air shows the glacier on September 1, 2017
Aerial photo courtesy of Brian Menounos (University of Northern British Columbia)‘If you take three or four decades of melt at a glacier in
the Coast Range—even a big one like Klinaklini—thecontribution to sea level rise is very small,’ said Jeffrey
Van Looy, a University of North Dakota glaciologist who
analysed changes at five ice fields in southern British
Columbia, including the Ha-Iltzuk Ice field that contains
Klinaklini Glacier. ‘But this is a region where we’retalking about thousands of glaciers, and several ice
fields are experiencing changes similar to this. And thesame thing is happening globally. All that melting starts
to add up.’According to one recent estimate, glaciers—excluding
the ice sheets on Greenland and Antarctica—lost an
average of 267 gigatons of mass per year between 2000
and 2019, equivalent to 21 percent of the observed sea
level rise during that period.
Van Looy’s analysis of weather patterns found thatrising temperatures and increases in rainfall, rather
than snowfall, in the Ha-Iltzuk Ice field are fuelling theice losses. More recent analysis by researchers fromthe University of Northern British Columbia showed thewarming pattern continued into the 2020s. ‘This is whatclimate change looks like,’ said Van Looy.
‘The total sea level rise potential of the western North
America glaciers—if they melted entirely—is only
about 2.6 millimetres,’ said Menounos. Other important
contributors to sea level rise, aside from the melting ofglaciers on land, include the melting of ice sheets in
Antarctica and Greenland, the thermal expansion of sea

water as it warms, and changes to how much water isstored on land. Projections made available by NASA’s
Sea Level Change Team suggest that Port Hardy,
a community 135 kilometres southwest of Klinaklini
Glacier, will likely see about 8 millimetres of sea level
rise by 2060 and 24 millimetres by 2100 under ‘middleof-the-road’ emissions scenarios.
‘The melting of these glaciers also raises importantwater resource issues since they provide cool, plentiful
water when seasonal snow has melted during timesof sustained droughts—like we’re having now,’ stated
Menounos. ‘Glacial meltwater is especially important for
many fish-bearing rivers.’
The names of both the Klinaklini Glacier and Klinaklini
River derive from the Kwak’wala word for eulachon
grease, which is made from a small oily fish. Eulachon—sometimes called smelt, hooligan, oolichan, fathom
fish, and salvation fish—have long been prized by First
Nation communities because early spring spawningprovides nutrition after long, cold winters.
While eulachon populations are considered stablein Alaska, more southerly populations in British
Columbia and Washington state are threatened andmoderately vulnerable to climate change, according to
the Washington Department of Fish and Wildlife. The
hatching of eulachon eggs is tied to peak spring flows
on rivers; changing precipitation patterns, reduced
snowpack, or earlier snowmelt associated with climatechange could affect the eulachon life cycle.

www.geo-web.org.uk

24

Worrying lack of snow in the Pyrenees
Copernicus Image of the Day

Credit: European Union, Copernicus Sentinel-2 imagery

Like many other countries in Europe, France has
experienced an unusually warm January this year, withtemperatures remaining above 0ºC in the French Pyrenees
region and, as a consequence, a lack of snow in thearea. Some ski resorts have temporarily closed due to thealmost complete absence of snow, while others have shut
down completely for this year’s ski season. This situation
will impact the local economy, which relies heavily on
winter tourism.
This image acquired by one of the Copernicus Sentinel-2
satellites shows the ski station of Gavarnie-Gèdre in the
French Pyrenean on January 30, 2024. The ski station willremain provisionally closed because of the snow drought.

The Copernicus Sentinel-1 satellite, uses radar imaging
to capture images of the Earth’s surface, even in thepresence of cloud cover or darkness. These images
enable it to map and track changes in snow and ice cover,including the extent of glaciers, sea ice and snow cover onland.
Sentinel-2 and Sentinel-3 also provide high-resolution
multispectral images used to map snow and ice cover. By
monitoring snow and ice cover over time, scientists canbetter understand the effects of climate change and otherenvironmental factors on these important ecosystems,
while utilities can estimate future hydro-power potential
production etc.

www.geo-web.org.uk

25

The Lovely Shape of Spirit Lake
NASA Earth Observatory
Story by Kathryn Hansen

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

Spirit Lake is resilient. The lake and once-popular
tourist site in south-central Washington was nearly
obliterated in May 1980 during the events that
unfolded around the cataclysmic eruption of Mount
St Helens. The lake survived, and it took on a
lovely new shape.
The OLI (Operational Land Imager) on Landsat 8
acquired this image on April 26, 2023. A whiteblanket of snow contrasts with the dark-blue water,emphasizing the lake’s heart-like shape whenviewed from above.
Prior to the eruption, Spirit Lake had a smaller
footprint that consisted of west and east arms
connected by a narrow span of water—similar inshape to the top-half of a heart. Then, on May 18,
1980, the volcano’s north flank let loose, producing
the largest-known landslide in recorded history,
followed by a lateral blast and shock wave as theeruption unfolded. The water in Spirit Lake wastemporarily displaced but eventually flowed backinto the basin.

A ‘new’ lake reformed atop the debris from thelandslide. The fully heart-shaped lake was broader
and shallower, and the elevation of its surface
higher by nearly 60 metres. Some of the landslidedebris formed a blockage, or natural dam, on thelake’s southwest side. Without an outlet, waterlevels continued to rise until engineers constructeda drainage tunnel in 1985.
From the 1920s through the 1970s, Spirit Lakedrew tourists to its shores. Cabins and lodges lined
the lake, and people could swim, boat, and fishin its waters. Today, those lakeside features areburied in avalanche debris below the modern lake.
Fishing and swimming are now prohibited, andaccess is limited to preserve the site as a naturallaboratory for studying the landscape’s recovery.
For example, scientists think that the trees
uprooted by the volcanic blast and still floating in
the lake, visible as the brown line in the detailed
image above, have become an important part of thelake’s ecosystem.

www.geo-web.org.uk

26

Cloud Vortices over the Atlantic
MODIS Image of the Day

Image Credit: MODIS Land Rapid Response Team, NASA GSFC

Winds blowing past the Canary Islands created fascinating
patterns in the clouds in late January 2024. The Moderate
Resolution Imaging Spectroradiometer (MODIS) on
NASA’s Terra satellite acquired this true-colour image on
January 22.
The cloud swirls downwind of the Canary Islands arecalled Von Kármán vortices, a distinctive pattern thatcan occur when a fluid passes a tall, isolated object. The
fluid splits around the object, creating a swirling eddy
downwind. Linear chains of these eddies are called vonKármán vortex streets. Fluids are materials that arecapable of flowing and easily changing shape. While mostpeople think of water as a fluid, air is also considered a
fluid.

In this case, the Von Kármán vortices occurred as windrushed past the tall volcanic peaks of the Canary Islands.
Heavy clouds behind the islands were caught up in the
swirling air, making the pattern easily visible from space.
Located in the Atlantic Ocean off the western coast of
Africa, the Canary Islands are a frequent location of suchcloud patterns.
Fluid dynamicist Theodore von Kármán was the firstto describe the conditions under which these turbulent
patterns occur. Von Kármán was a professor of
aeronautics at the California Institute of Technology andone of the principal founders of NASA’s Jet Propulsion
Laboratory.

www.geo-web.org.uk

27

Cyclone Belal hits La Reunion and Mauritius
Copernicus Image of the Day

Credit: European Union, Copernicus Sentinel-3 imagery

On 15 January 2024, Cyclone Belal hit Mauritius andthe French island of La Réunion, bringing torrential rain
and strong winds to the region. At least one casualty
was reported in La Réunion, where a level three cyclone
warning had been issued, and a quarter of the population

had been left without electricity and drinking water. This
image of Cyclone Belal was acquired by one of theCopernicus Sentinel-3 satellites on January 15, 2024 at
05:45 UTC while it passed through Saint-Denis and PortLouis.

www.geo-web.org.uk

28

The Zahara-El Gastor Water Reservoir has reached Critical Levels
Copernicus Image of the Day

Credit: European Union, Copernicus Sentinel-2 data

The Zahara-El Gastor reservoir in southern Spain is a vital source of water for agriculture and recreation. The criticaldrought affecting the province of Cádiz has left the reservoir at nearly 6% of its capacity, a worrying level that threatens
access to water for surrounding communities. The lack of water is clearly visible in this Copernicus Sentinel-2 image ofthe Zahara reservoir acquired on February 2, 2024.
Open data retrieved by the Copernicus Sentinel satellites provide key information useful for accurately mapping lakes
and reservoirs and extracting critical information about changes in their water levels.

www.geo-web.org.uk

29

Badwater Basin Refills
NASA Earth Observatory
Story by Lindsey Doermann

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

An ephemeral lake in Death Valley’s Badwater
Basin [1] is showing its staying power. After formingin August 2023, in the aftermath of Hurricane
Hilary, the lake gradually shrank but persisted
throughout the fall and winter. A potent atmosphericriver refilled it during February 2024.
This series of images compares the desert basin
before flooding (left) with its more-waterlogged
state following each major storm. In both August2023 (middle) and February 2024 (right), a shallow
lake several kilometres across fills in the low-lying
salt flat. The images were acquired by the OLI(Operational Land Imager) sensor on Landsat 8 (leftand right) and the OLI-2 on Landsat 9 (middle).
They are false-colour, shown with the OLI and OLI-2
band combination of 6-5-3, which emphasizes thepresence of water in shades of blue.
The driest place in North America, Death Valley
typically receives about 51 millimetres of rain
per year. However, in the past six months alone,
more than double that, 125 millimetres, fell at the

National Park’s official weather gauge at Furnace
Creek. Two events were responsible for most ofthat precipitation. According to park officials,
the remnants of Hurricane Hilary delivered 66
millimetres on August 20, 2023, and an atmosphericriver supplied another 45 millimetres between
February 4–7, 2024.
Following the August deluge, ‘most of us thought thelake would be gone by October,’ said Death Valley
National Park ranger Abby Wines in a news release.
‘We were shocked to see it still here after almost
six months.’ That was before the rains returned in
February.
After the early February atmospheric river moved
through, observers on the ground saw the lake
continue to expand as water drained into the area.
On February 11, park ranger Matthew Lamar noted:‘The Amargosa River [which feeds the basin from thesouth] is really flowing, and we’ve noticed the waterlevel continue to rise over the last couple of days aswaters make their way to the basin.’www.geo-web.org.uk

30

Snow-capped hills are reflected in the ephemeral waters of Badwater Lake
Photo by K. Skilling/National Park Service

Basin is endorheic, meaning that water flows into
but not out of it. Typically, evaporation far outpaces
inputs, rendering the lake ephemeral. But in thepast six months, the influxes have changed theequation.
Based on satellite imagery, the lake appears to havegrown to a similar size in February 2024 as it didin August 2023, thereby extending its months-longtenure. This comes as welcome news to visitors, whohave enjoyed witnessing stunning reflections of thesurrounding peaks in its calm waters.

As of February 14, the lake is 30 centimetres deep inplaces, according to park officials, and it is uncertain
how long this will last. Past appearances of thelake are rare and offer little insight into the current
situation: when a lake formed in 2005, for example,
it reportedly lasted about one week. It is also too
early to know how the precipitation will affect thewildflower season, which runs from late-February to
mid-April.
Reference

1 Floodwaters in Badwater Basin - GEO Quarterly No 80, page 26

www.geo-web.org.uk

31Volcanic activity at the Popocatepétl Volcano
Copernicus Image of the Day

Credit: European Union, Copernicus Sentinel-2 imagery

Popocatépetl is a stratovolcano in central Mexico, formed by the subduction of the Cocos Plate beneath the North
American Plate. Its eruptions are predominantly explosive, driven by the build-up of gas pressure in the magma
chamber. It is closely monitored due to its proximity to densely populated areas such as Mexico City and La Puebla.
The activity of the Popocatepetl increased during February and this image, acquired on February 10 by one of theCopernicus Sentinel-2 satellites, shows a massive ash plume drifting some twenty kilometres to the northeast.
The Copernicus Sentinel satellites support the surveillance of volcanoes worldwide, proving particularly adapted tomonitoring volcanoes located in remote regions.

www.geo-web.org.uk

32
32

A Rare Tropical Storm in the South Atlantic
NASA Earth Observatory
Story by Emily Cassidy

Tropical storms seldom roam in
the South Atlantic Ocean. But
in mid-February 2024, one suchstorm did form off the coast of
Brazil.
The disturbance began to develop
as a stalled front of low pressure
on February 15. According toresearchers at NOAA’s Cooperative
Institute for Meteorological
Satellite Studies (CIMSS), thefront developed into a subtropicaldepression on February 16 after
being fed by a plume of tropicalmoisture that plunged south. The
depression continued to intensify
and move south, and at 9 pm
local time on February 18 (00:00
Universal Time on February 19)
the Brazilian Navy Hydrographic
Center upgraded it to Tropical
Storm Akará. At the time, thestorm carried sustained winds of
up to 64 kilometres per hour.
The MODIS (Moderate Resolution
Imaging Spectroradiometer)
instrument on NASA’s Aqua
satellite captured this image of
Akará around 2:20 pm local time
(17:20 Universal Time) on February
19, 2024, when its centre wasabout 900 kilometres southeast of São Paulo.

NASA Earth Observatory image by Lauren Dauphin, using
MODIS data from NASA EOSDIS LANCE and GIBS/Worldview

Until the start of the 21st century, tropical cyclones
in the South Atlantic were undocumented. According
to meteorologists at Yale Climate Connections, wind
shear was often too high for storm formation, andeasterly waves from northern Africa—which seedcyclones and hurricanes in the Atlantic—are not a
regular occurrence south of the equator.
In 2004, a rare tropical cyclone formed in thisregion and eventually made landfall in Brazil’s
southern state of Santa Catarina. The National
Hurricane Center in Miami estimated the storm to
be a category‑1 hurricane (named Catarina), making
it the first hurricane observed in the South Atlantic
during the satellite record. At the time, the Brazilian
Center for Weather Prediction did not operate anyanemometers in the area or have any hurricane
hunter aircraft to fly through the storm. All estimates
were based on satellite data only.
After Catarina, forecasters paid closer attention
to storm development in the South Atlantic. Since
2015, three other tropical storms have been recordedin the basin: Tropical Storm Iba in 2019, Tropical
Storm 01Q in 2021, and now Akará in 2024.
Warm sea surface temperatures most likely
contributed to Akará’s formation. According to Yale
Climate Connections: “Sea surface temperatures inthe vicinity of Akará on Monday were around 0.5°C
warmer than average, at around 26°C, or what’s
typically considered to be the minimum threshold fortropical development.” This unusually warm water
is more typical of temperatures in early summer,
they noted, continuing a trend of warm sea surface
temperatures that has persisted for months.
Akará was expected to remain well offshore and nothave major impacts on land, aside from high surfalong the coast south of Rio de Janeiro. Forecasts
showed the storm weakening as it headed south overcooler waters.
Editor’s Note
For a full explanation as to why South Atlantic Hurricanes
rarely form, see Peter Wakelin’s article: “Why are south
Atlantic Hurricanes so Rare?” in GEO Quarterly No 2(2004), available from the on-line back-issue archive.

www.geo-web.org.uk

33

Winter on the Tibetan Plateau
MODIS Web Image of the Day

Image Credit: MODIS Land Rapid Response Team, NASA GSFC

On February 10, 2024, crystal-clear skies over the
Tibetan Plateau allowed the Moderate Resolution Imaging
Spectroradiometer (MODIS) on NASA’s Terra satellite tocapture a true-colour image of winter at the ‘Roof of theWorld’.

This high plateau is home to more than 1,500 lakes ofassorted sizes and characteristics. Many are quite saline,
while others are filled with fresh water. Some are fed byglaciers while some give rise to many of Asia’s majorrivers, including the Ganges, Yangtze and Mekong.

Sitting north of the Himalayas and south of the Kunlun
Mountains, the Tibetan plateau stretches more than
1000 kilometres from north to south and 2500 kilometresfrom east to west. It has earned its nickname because of
its extremely high elevation, which averages more than
4,500 metres. In the north and northwest, elevations rise to
5,000 metres.

Frigid winter temperatures cause freshwater lakes andrivers to ice over completely, and these appear white inthis image.
More saline lakes are partially frozen, while a few very
deep and salty lakes remain ice-free and shine likesapphires in the winter landscape.

www.geo-web.org.uk

34

Currently Active Satellites and Freqencies
Polar APT Satellites
Satellite

Frequency

StatusFormatImage Quality

NOAA 15

137.6200 MHz

On

APT

Intermittent sync problem

NOAA 18

137.9125 MHz

On

APT

Good

NOAA 19137.1000 MHz

On

APT

Good

Meteor M N2

137.1000 MHz

On

LRPT

FailedMeteor M N2-3

137.9000 MHz

Off

LRPT

Variable [1]Satellite

Frequency

Mode

FormatImage Quality

NOAA 151702.5 MHz

Omni

HRPT

sync problem

NOAA 18

1707.0 MHz

RHCP

HRPT

Good

NOAA 19

1698.0 MHz

RHCP

HRPT

Good

Feng Yun 3C

1701.4 MHz

RHCP

AHRPT

Inactive [2]Feng Yun 3D

7820.0 MHz

RHCP

AHRPT

Active {2}Polar HRPT/AHRPT Satellites

Feng Yun 3E

7860.0 Mz

RHCP

AHRPT

Commissioning

Metop B

1701.3 MHz

RHCP

AHRPT

Good

Metop C

1701.3 MHz

RHCP

AHRPT

Good

Meteor M N2-2

1700.0 MHz

RHCP

AHRPT

Active [8]Meteor M N2-3

1700.0 MHz

RHCP

AHRPT

ActiveGeostationary Satellites
Satellite

Transmission Mode(s)Position

Status

45.5°EIODC - On

Meteosat 9

HRIT (digital)

Meteosat 10

HRIT (digital)

LRIT (digital)

0°W

Off [4]

Meteosat 11

HRIT (digital)

LRIT (digital)

9.5°E

On [3]

0.4°W

Commissioning

GOES-13GVAR 1685.7 MHz

LRIT 1691.0 MHz

61.6°E[5]

GOES-14GVAR 1685.7 MHz

LRIT 1691.0 MHz

105°W

Standby

MTG-l1

GOES-15 (W)GVAR 1685.7 MHz

LRIT 1691.0 MHz

135°W

Off (in storage)

GOES-16 (E)GRB 1686.6 MHz

HRIT 1694.1 MHz

75.2°W

On [7]

GOES-17

GRB 1686.6 MHz

HRIT 1694.1 MHz

104.7°W

Off

GOES 18

GRB 1686.6 MHz

HRIT 1694.1 MHz

137.0°W

On [7]

Himawari-8

No direct download

On

No direct download

Data is only available
via the HimawariCast
service140.7°E

Himawari-9

140.7°E

On

Feng Yun 2E

SVISSR (digital)

LRIT (digital)

86.5°EOff

Feng Yun 2F

SVISSR (digital)

LRIT (digital)

112.5°E

Standby

Feng Yun 2G

SVISSR (digital)

LRIT (digital)

105.0°E

On

Feng Yun 2H

SVISSR (digital)

LRIT (digital)

79.0°EOn

Feng Yun 4A

HRIT (digital)

LRIT (digital)

99.5°EOn

Feng Yun 4B

HRIT (digital)

LRIT (digital)

105°E

On

Notes
1
2
3
4
5
6
7
8
9

Currently, M2-3 transmits on 137.9 MHz but has on occasions switched to 137.1 MHz.
Transmission is currently on a Symbol Rate of 72,000 baud, though 80,000 baud has been used in trials.
These satellites employ a non-standard AHRPT format and cannot be received with conventional receiving
equipment.
Meteosat prime Full Earth Scan (FES) satellite
Meteosat prime Rapid Scanning Service (RSS) satellite.
Repurposed for use by the US Space Force
GOES 15 also transmits EMWIN on 1692.700 MHz GOES 16 also transmits EMWIN on 1694.100 MHz GOES 17
also transmits EMWIN
GOES Rebroadcast (GRB) provides the primary relay of full resolution, calibrated, near-real-time direct broadcast
space relay of Level lb data from each instrument and Level 2 data from the Geostationary Lightning Mapper (GLM).
GRB replaces the GOES VARiable (GVAR) service.
Following a collision with a micrometeorite, the power system aboard Meteor M2-2 has been compromised. AHRPTis still being transmitted when the solar panels are sunlit, but there is insufficient battery power to enable the LRPT
stream.
Japanese satellites MTSAT-1R (Himawari-6) and MTSAT-2 (Himawari-7) are no longer active and are probably
retired. Current Japanese operational geostationary satellites are Himawari-8 and Himawari-9.

www.geo-web.org.uk

35