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Monster iceberg ‘A23a’ just shy of a trillion tonnes

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Scientists now have good numbers to describe the true scale of the world’s biggest iceberg, A23a.

Satellite measurements show the frozen block has a total average thickness of just over 280m (920ft).

Combined with its known area of 3,900 sq km (1,500 sq miles), this gives a volume of roughly 1,100 cubic km and a mass just below a trillion tonnes.

The iceberg, which calved from the Antarctic coast in 1986, is about to drift beyond the White Continent. It has reached a critical point in its journey, researchers say, with the next few weeks likely to decide its future trajectory through the Southern Ocean.

A23a viewed from Royal Research Ship Sir David Attenborough
As far as the eye can see: A23a is more than twice the area of Greater London (pic BBC)

To put the new thickness data in some context, London skyscraper 22 Bishopsgate is 278m tall – bettered, in the UK, by only the 310m Shard tower.

But A23a is also more than twice the area of Greater London, giving it an overall profile much like that of a credit card.

TwentyTwo
22 Bishopsgate is the UK’s second-tallest skyscraper (pic BBC)

The measurements of A23a come from the European Space Agency’s CryoSat-2 mission. This veteran spacecraft carries a radar altimeter able to sense how much of a berg’s bulk is above the waterline.

Using information about the density of ice, it is then possible to determine how much must be submerged.

“Altimetry satellites like CryoSat-2, which measure the distance to the iceberg surface and to the sea surface, allow us to monitor iceberg thickness from space,” Dr Anne Braakmann-Folgmann, from the University of Tromsø – The Arctic University of Norway, told BBC News.

“They also enable us to watch the iceberg thinning as it gets exposed to warmer ocean waters. “And together with knowledge of the sea-floor topography, we know where an iceberg will ground or when it has thinned enough to be released again.”

Lost thickness over time

When the berg started moving, after 2020, it became increasingly difficult to obtain broad thickness measurements. But assuming an area of 3,900 sq km and an average total thickness of 285m, then A23a has a volume of 1,113 cubic km and a mass of 950 billion tonnes.

Presentational grey line

Born in a mass breakout of bergs from the Filchner Ice Shelf, in the southern Weddell Sea, A23a was almost immediately stuck in shallow bottom muds to become an “ice island” for more than three decades. And the CryoSat data can now explain why.

The berg is not a uniform block – some parts are thicker than others.

CryoSat indicates one section in particular has a very deep keel, which in 2018, had a draft – the submerged portion of an iceberg – of almost 350m and it is this section that anchored A23a for so long.

Satellite images show crevasses directly above the keel.

“This is likely the surface expression of the damage that was caused when A23a hit the seabed,” Prof Andrew Shepherd, from Northumbria University and the Natural Environment Research Council Centre for Polar Observation and Modelling (CPOM), said.

Edge of A23a
A23a: Most of an iceberg’s bulk sits below the waterline (pic BBC)

And in the years that followed, A23a gradually lost mass to eventually free itself and start moving.

“Over the last decade, we have seen a steady 2.5m per year decrease in thickness, which is what you would expect given the water temperatures in the Weddell Sea,” Dr Andy Ridout, a CPOM senior research fellow from University College London, explained.

A23a has now reached the tip of the Antarctic Peninsula, where there is a convergence of various streams of fast-moving water that turn clockwise around the continent.

How it interacts with these and the westerly winds that dominate in that part of the world will control where the behemoth goes next.

But it is expected take a track called “iceberg alley” that points in the direction of the British overseas territory of South Georgia.

Iceberg comparison

Scientists will follow its progress with interest.

Bergs this big have a profound influence on their environment. “They’re responsible for very deep mixing of seawater,” Prof Mike Meredith, from the British Antarctic Survey, told BBC News. “They churn ocean waters, bringing nutrients up to the surface, and, of course, they also drop a lot of dust.

“All this will fertilise the ocean – you’ll often see phytoplankton blooms in their wake.”

(BBC)



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Trump administration mulls new travel ban that could hit 43 nations: Report

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[file pic] Protesters rally outside the US Supreme Court, while the court considers a case regarding presidential powers as it weighs the legality of President Donald Trump's latest travel ban on people from Muslim-majority countries [Aljazeera]

United States President Donald Trump’s administration is mulling a new travel ban that is expected to affect citizens from dozens of countries to varying degrees, The New York Times reported.

Quoting anonymous officials, the report published on Friday said the US government’s draft list featured 43 countries, divided into three categories of travel restrictions.

The first group of 10 countries, including Afghanistan, Iran, Syria, Cuba and North Korea, would be set for a full visa suspension.

In the second group, five countries – Eritrea, Haiti, Laos, Myanmar and South Sudan – would face partial suspensions that would affect tourist and student visas as well as other immigrant visas, with some exceptions.

In the third group, a total of 26 countries that includes Belarus, Pakistan and Turkmenistan would be considered for a partial suspension of US visa issuance if their governments “do not make efforts to address deficiencies within 60 days”, the draft memo said.

A US official speaking on condition of anonymity told the Reuters news agency there could be changes to the list and it was yet to be approved by the administration, including US Secretary of State Marco Rubio.

Trump issued an executive order on January 20 requiring intensified security vetting of any foreigners seeking admission to the US to detect national security threats.

The order directed several cabinet members to submit by March 21 a list of countries from which travel should be partly or fully suspended because their “vetting and screening information is so deficient”.

The US president’s directive is part of an immigration crackdown he launched at the start of his second term. He previewed his plan in an October 2023 speech, pledging to restrict people from the Gaza Strip, Libya, Somalia, Syria, Yemen and “anywhere else that threatens our security”.

The latest travel ban proposal, however, harkens back to Trump’s first-term ban on travellers from seven Muslim-majority nations, a policy that went through several iterations before it was upheld by the Supreme Court in 2018.

That ban targeted citizens of Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen and ignited international outrage and domestic court rulings against it. Iraq and Sudan were later dropped from the list, but in 2018 the Supreme Court upheld a later version of the ban for the other nations as well as North Korea and Venezuela.

[Aljazeera]

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At least 20 dead as tornadoes tear through southern US

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[pic BBC]

At least 20 people have died in the US – including 12 in Missouri alone – after deadly tornadoes tore through several south-eastern states, flipping cars and flattening homes.

Three people were killed in a car crash during a fierce dust storm in Texas, while deaths have also occurred in Oklahoma and Arkansas.

More than 240,000 properties were without power across six states – including Texas, Missouri and Illinois – on Saturday afternoon, according to tracker PowerOutage.

Further severe weather is expected for the region, with tornado watches issued in central Mississippi, eastern Louisiana and western Tennessee.

Flash flooding and flood warnings have also been issued in the same three states, as well as parts of Alabama and Arkansas, as severe weather continues to track across the south-east.

The National Weather Service (NWS) has said these flash floods could prove deadly.

A tornado warning – the highest level of alert – was also issued in central Mississippi on Saturday morning.

The NWS warned of “multiple intense to violent long-track tornadoes” in those areas, describing the situation as “particularly dangerous”.

The meteorological agency said: “If you live in these areas, get to the sturdiest structure you have access to and remain in place until the storms pass.”

Mike Kehoe, governor of Missouri, said the state had been “devastated by severe storms and tornadoes, leaving homes destroyed and lives lost”.

Missouri’s emergency management agency said initial reports indicated 19 tornadoes had struck 25 counties so far.

Arkansas has seen three deaths and 29 injuries – prompting Governor Sarah Huckabee Sanders to declare a state of emergency.

Georgia’s governor, Brian Kemp, also declared a state of emergency ahead of a predicted severe weather pattern hitting his state.

The NWS expects the threat of tornadoes to spread into Alabama, Florida and Georgia into Sunday.

Meanwhile, one person died on the road in Oklahoma, the BBC’s US partner CBS News reported, citing officials.

The same dust storm that caused three deaths in Texas on Friday night caused a pile-up of an estimated 38 cars.

“It’s the worst I’ve ever seen,” Sgt Cindy Barkley, of the state’s department of public safety, told reporters.

“We couldn’t tell that they were all together until the dust kind of settled.”

A further death has since been reported in Texas.

In Texas and Oklahoma, the destructive storms fuelled more than 100 wildfires and overturned several semi-trailer trucks, CBS reports.

One of those fires, known as the 840 Road Fire, has already burned 27,500 acres and remains 0% contained, according to the Oklahoma Forestry Service. The agency has issued a “red flag” warning for the state’s panhandle area, signalling a severe fire danger.

Tornadoes form when moist, warm air rises, mixing with cold air above to form thunderclouds. Winds blowing from different directions cause the air to rotate, creating a vortex of air moving upwards.

The four states where tornado-related deaths have been confirmed in the past day lie within a path frequently hit by the weather phenomenon.

It has earned this stretch of the US the unofficial name Tornado Alley, because its geography is ideal for tornado formation.

In 2024, 54 people were killed in tornado-related incidents, according to Noaa,  Nine people died in Texas. There were eight in Oklahoma, five in Arkansas and one in Missouri.

Peak tornado season in Tornado Alley is from May to June – but meteorologists caution that tornadoes can occur at any time of year.

[BBC]

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US launches wave of air strikes on Yemen’s Houthis

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The US has launched a “decisive and powerful” wave of air strikes on Houthi rebels in Yemen, President Donald Trump has said, citing the armed group’s attacks on shipping in the Red Sea as the reason.

“Funded by Iran, the Houthi thugs have fired missiles at US aircraft, and targeted our Troops and Allies,” Trump wrote on his Truth social platform, adding that their “piracy, violence, and terrorism” had cost “billions of dollars” and put lives at risk.

The Houthi-run health ministry said at least 13 people were killed and nine others injured in the strikes.

The group – which began targeting shipping in response to the Israel-Hamas war in Gaza – said its forces would respond to US strikes.

In a statement, the Houthis blamed the US and the UK for “wicked” aggression targeting residential areas in the Yemeni capital, Sanaa – though it is understood that the UK was not behind Saturday’s strikes on the Middle Eastern country.

The Iranian-backed rebel group,  considers Israel its enemy. It controls Sanaa and the north-west of Yemen, but it is not the country’s internationally-recognised government.

Since the start of the war between Israel and Hamas, it has launched hundreds of attacks on commercial vessels travelling through the Red Sea.

These attacks, Trump said, “will not be tolerated”.  “We will use overwhelming lethal force until we have achieved our objective.”

Initially, the group said it was attacking ships connected with, or that had docked in, Israel. However, many of the vessels have no connection with Israel.

Trump said that it had been more than a year since a US-flagged ship had sailed safely through the Suez Canal – which the Red Sea leads to – and four months since a US warship had been through the body of water between east Africa and the Arabian peninsula.

The Suez Canal is the quickest sea route between Asia and Europe, and is particularly important in the transportation of oil and liquefied natural gas (LNG).

Addressing the Houthis directly, Trump wrote that if they did not stop, “HELL WILL RAIN DOWN UPON YOU LIKE NOTHING YOU HAVE EVER SEEN BEFORE”.

But the Houthis were unwavering in their response, saying the aggression would not wane their support for Palestinians.

“This aggression will not go without response and our Yemeni armed forces are ready to answer escalation with further escalation,” the group said.

Meanwhile, US Defence Secretary Pete Hegseth said that the Houthi’s “benefactor”, Iran, was “on notice”.

Map showing where Sanaa is in relation to the Red Sea, Israel, eastern Africa and the Arabian Peninsula.

For more than a year, major shipping companies were forced to stop using the Red Sea – through which almost 15% of global seaborne trade usually passes – and used a much longer route around southern Africa instead.

The Houthis launched 190 attacks in the Red Sea between November 2023 and October 2024, according to the US Congress.

Previously, the UK and US conducted joint naval and air strikes against the group. Israel has also targeted sites linked to the Houthis in separate strikes.

Trump urged Iran to cease its support for the Houthis, warning that Washington would hold Tehran “fully accountable and, we won’t be nice about it”.

He also accused the previous White House administration, under Joe Biden, of being “pathetically weak” and allowing the “unrestrained Houthis” to keep going.

[BBC]

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