Alaska’s 2025 mega tsunami highlights risk to cruise lines as glaciers retreat. Researchers say 481-metre wave in fjord was triggered by rockslide linked to climate crisis

 

Glaciers in Alaska's Denali national park have been found to be melting faster than at any time in the past four centuries due to rising summer temperatures. Photograph: VW Pics/Universal Images Group/Getty Images

by Maya Yang

A mega tsunami in Alaska last year in a fjord visited by cruise ships is a stark warning of the risks of coastal rockslides and glacier retreat fueled by the climate crisis, a new study warns.

Scientists recorded the world’s second-tallest tsunami after it struck the Tracy Arm fjord in south-east Alaska last August after a massive rockslide around the toe of a glacier. The tsunami reached 481 metres (1,578ft) in height; by comparison the Eiffel Tower is 330 metres (1082ft).

According to the new research published in Science on Wednesday and led by Dan Shugar, a geomorphologist of the University of Calgary, the sequence began at 5.26am local time on 10 August 2025. A large landslide collapsed 1km vertically onto the South Sawyer glacier and into the narrow, 48km fjord, producing the huge tsunami.

An oblique aerial photograph of Sawyer Island, largely stripped of trees, taken during a US Geological Survey reconnaissance flight on 13 August 2025. Photograph: John Lyons/U.S. Geological Survey.

There were no fatalities at the early hour but the area is visited by approximately three cruise ships passing through daily, along with other vessels traveling within a few kilometers of the landslide site.

 

Just hours after the landslide, a sightseeing vessel from Juneau and a National Geographic tour boat – each capable of carrying more than 100 passengers, were due to enter the fjord. The day before, two cruise ships carrying thousands of passengers had already visited the area, with another scheduled to arrive the following day.

At the time of the event, Dennis Staley from the US Geological Survey called the tsunami “a historic event”, adding to the Guardian: “I feel like we dodged a bullet.”

“With fjord regions increasingly visited by cruise ships, and climate change making similar events more likely, this unanticipated, near-miss event highlights the growing risk from landslides and tsunamis in coastal environments,” researchers said in their report.

A near-source animation of the tsunami generated by the August 10, 2025 Tracy Arm landslide.

 

They also noted that the tsunami was only slightly smaller than the world’s tallest, recorded in Lituya Bay, Alaska, in 1958 at 530 metres (1,728ft). The Tracy Arm event also triggered a 36-hour seiche – a standing wave that oscillates within a closed body of water.

The study further found that the landslide generated long-period seismic waves equivalent to those of a 5.4 magnitude earthquake.

Eyewitness accounts in the report highlighted the tsunami’s far-reaching effects. A group of kayakers camping on Harbor Island, about 55km away, reported water surging past their tent, sweeping away one of their kayaks along with other gear.

Another observer aboard a motor vessel in No Name Bay, roughly 50km from the landslide, described seeing a 2 to 2.5 metre wave cresting along the shoreline from the direction of Tracy Arm, followed by a second wave of about 1 metre, the researchers said.

In the study, researchers found that landslide-generated tsunamis can “have substantially higher runups (the maximum height water reaches on a slope) than earthquake tsunamis, owing to larger, localized variations in water depth and direct water-column displacement by slope failure – most pronounced in confined water bodies like fjords”.

Pointing to climate crisis-driven glacier retreat, researchers noted that “without the rapid glacier retreat, the landslide would likely not have resulted in such a wave because it would have collapsed entirely onto glacier ice or might not even have occurred at all”.

In recent years, fjords with retreating tidewater glaciers have become increasingly popular destinations for cruise ships. According to the study, annual cruise passenger numbers in Alaska have risen from about 1 million in 2016 to 1.6 million in 2025.

Aerial photographs show a clear trimline along the far side of the fjord where a tsunami stripped vegetation from the slopes. Photograph: John Lyons/U.S. Geological Survey

Combined with accelerating glacier retreat and permafrost degradation driven by the climate crisis, the risk of large-scale landslide-generated tsunamis is also increasing across the Arctic.

As a result, researchers emphasized both the scale and potential reach of such events. They called for stronger risk mitigation measures, including systematic monitoring of unstable slopes, more realistic tsunami-modeling scenarios and enhanced protection for local communities, tourists and critical infrastructure.

Several tsunamis have occurred in Alaska over the last decade, with a large landslide generating a 18 to 55 metre wave in Kenai fjords national park in 2024, as well as another landslide near a receding glacier in Taan fjord in south-east Alaska that caused a 193 metre tsunami in 2015.

Alaskan River Reaches Record High From Melting Glacier. An overflowing glacial lake caused a surge in the Mendenhall River on Wednesday, prompting flood alerts and evacuations in Juneau.

 

A timelapse view from cameras monitored by the U.S.G.S. of the Suicide Basin before the glacial lake outburst flooding from the Mendenhall Glacier, in Juneau, Alaska, covering a period from July 21 to Aug. 13.CreditCredit...U.S.G.S.

 

By Raymond Zhong

 

An overflowing glacial lake north of Juneau, Alaska, caused the Mendenhall River to surge to a record height on Wednesday, flooding homes and streets in parts of the state capital, which has a population of more than 30,000.

Such floods have been a recurring problem in Juneau since 2011, but recent years have seen record-setting surges as rising temperatures cause glaciers in the area to melt more rapidly. Alaska has warmed faster than the global average, and the fastest of any state, according to the Environmental Protection Agency.

Flooding last August from the same glacial lake inundated several hundred homes in Juneau with four to six feet of water, although no deaths or injuries were reported. The city put up a temporary levee along the river in response. Residents this week were urged to evacuate ahead of the latest round of high water.

Here’s what to know about these floods.

What’s a glacial lake outburst flood, or GLOF?

As glaciers melt, they tend to retreat uphill, leaving an empty bowl at the bottom of the valley where the ice once sat. Meltwater from the glacier starts pooling in this bowl, and over time a lake forms.

 But the sides of the lake are fragile. They might be formed of loose dirt and rock or ice. If one day an avalanche or a landslide occurs, or a piece of a nearby cliff plunges into the water, the disturbance can cause the sides of the lake to collapse. In a flash, most of the lake’s water might cascade down the valley, threatening towns and cities below.

 

Glacial lake outburst floods can be catastrophic because, by the time the water reaches downstream settlements, it has picked up huge amounts of sediment and boulders along the way, turning it into a thick slurry that can knock down buildings.

In 2023, a GLOF in northern India killed at least 55 people and destroyed a hydropower dam. All in all, 15 million people around the world live within 50 kilometers, or 31 miles, of a glacial lake and less than a kilometer from the potential path of a GLOF, scientists estimated in a 2023 study.

How common are they in Alaska?

The glacial lake that is overflowing this week in Alaska sits at the foot of the Suicide Glacier, an ice mass north of Juneau. Decades ago, the Suicide Glacier flowed into a much larger river of ice, the Mendenhall Glacier. But as the Suicide melts and shrinks, a steep gap has opened up between it and the Mendenhall. This gap is now called Suicide Basin.

(Experts have proposed renaming Suicide Basin to Kʼóox Ḵaadí Basin, which in the Tlingit language translates to “Marten’s Slide Basin.” A marten is a lithe, weasel-like animal found in the area.)

Snowmelt and rain accumulate in the basin, and when the water is high enough, it starts draining through cracks in the Mendenhall Glacier before flooding the Mendenhall River.

The first time this happened was in July 2011, and it took downstream communities by surprise. The basin has since filled and drained at least 39 times, according to the National Weather Service. Early Wednesday, as the basin drained once more, the Mendenhall River peaked at a height of 16.65 feet, exceeding a record set last year.

The glaciers in this region are part of the Juneau Ice Field, a sprawling area of interconnected ice that is melting twice as quickly as it did before 2010, scientists reported last year. More of the area’s glaciers are detaching from one another, the researchers also found, which can lead to the formation of lakes like Suicide Basin.

Accelerated melting is producing more water to fill these lakes and hence more water that eventually floods neighborhoods downstream, said Bob McNabb, a glaciologist at Ulster University who has studied the Juneau Ice Field. “As you get more and more melting coming down, that will fill up the basin a bit more each time,” Dr. McNabb said.

How is climate change affecting GLOFs?

The world’s high mountains are warming more quickly than Earth as a whole. That is causing thousands of glaciers to shrink and new lakes to form beneath them. Since 1990, the number, area and volume of glacial lakes around the world have all grown by roughly 50 percent, scientists estimated in a 2020 study.

But bigger lakes don’t directly translate into greater GLOF hazards. Each glacial lake and valley has distinct features that influence how likely it is to burst, and what the consequences would be if it did. So predicting future flood risks is “very complex,” Dr. McNabb said.

In the Mendenhall Valley, for instance, rising temperatures are the reason the Suicide Glacier has withered away and Suicide Basin has formed. But as the planet warms further, the Mendenhall Glacier might melt by so much that the flood threat actually decreases. The reason? There would no longer be enough ice at the side of Suicide Basin to trap large amounts of meltwater. Instead, the water would just empty into the valley gradually.

Scientists in Alaska have predicted that this could come to pass within the next decade or two. Until then, the people of Juneau will continue to live with the dangers from the warming landscape just a few miles to their north.

Ocean Heat Wiped Out Half These Seabirds Around Alaska - About four million common murres were killed by a domino effect of ecosystem changes, and the population is showing no signs of recovery, according to new research.

 Rescued common murres were placed into a special enclosure to dry after examination at a bird rescue center in Cordelia, Calif., in 2015.Credit...Randall Benton/The Sacramento Bee, via Associated Press

 

By Catrin Einhorn

 

The first evidence was the feathered bodies washing up on Alaskan beaches. They were common murres, sleek black-and-white seabirds that typically spend months at a time away from land. But in 2015 and 2016, officials tallied 62,000 emaciated corpses from California to Alaska.

Since then, scientists have been piecing together what happened to the birds, along with other species in the northeast Pacific that suddenly died or disappeared. It became clear that the culprit was an record-breaking marine heat wave, a mass of warm water that would come to be known as the Blob. New findings on its effect on murres, published on Thursday in the journal Science, are a stark sign of the perils facing ecosystems in a warming world.

 “What we learned was that it was just way worse than we thought,” said Heather Renner, one of the study’s authors and a supervisory wildlife biologist at the Alaska Maritime National Wildlife Refuge.

 

About half of Alaska’s common murres, some four million birds, died as a result of the marine heat wave, the scientists found. They believe it is the largest documented die-off of a single species of wild birds or mammals. The state is home to about a quarter of the world’s common murres, scientists say.

Murres were the victims of a domino effect of oceanic changes tied to the warm water, according to a growing body of research. It affected marine life from plankton to humpback whales. Critically for the murres, it led to a collapse in the fish they depend on.

 One of the most sobering revelations in the new study is that the birds have not even begun to rebound.

 

A murre colony in the Alaska Maritime National Wildlife Refuge, seen before and after the 2015-16 marine heat wave.Credit...U.S. Fish and Wildlife Service

 

 “If the foraging conditions are good, I think there’s hope,” Ms. Renner said. “Our fear is that events like this are predicted to become much more common, and we haven’t seen any signs of recovery at all yet, eight years after the event.”

 

 

For decades, the world’s oceans have absorbed more than 90 percent of the excess heat produced as humans burn fossil fuels and destroy ecosystems like forests. That heat has taken a severe toll on coral reefs, kelp forests and other marine ecosystems. Last year and into this year, the ocean’s surface temperature shattered records.

For the murres, earlier mortality estimates from the Blob were lower. In 2020, a team of some of the same scientists estimated that half a million to a million of the birds had died in Alaska. But the new research uses a different and far more reliable method, leveraging earlier data to analyze before and after counts at 13 breeding colonies throughout the Gulf of Alaska and the Eastern Bering Sea. The authors then extrapolated those declines across the entire population.

“We saw exactly the same really clear signal at every single colony,” Ms. Renner said. “It wasn’t some of them, it was all of them.”

Avian flu has had huge impacts on some bird populations around the world, but researchers have not seen much to date in Alaska, Ms. Renner said, so it does not appear to be playing a major role.

Notably, while various species were pummeled by the Pacific marine heat wave, including some fisheries stocks, not all showed declines. That suggests the oceanographic changes created “pinch points” in the food web rather than, say, taking out all predators.

 

Mark Mallory, a seabird biologist and professor at Acadia University in Nova Scotia who was not involved with the study, said the research highlighted the critical importance of long-term monitoring data in allowing scientists to understand the extraordinary changes underway on Earth.

The finding that murres, typically a resilient species, are not regaining their numbers, reminded him of what happened when people overfished Atlantic cod stocks off Newfoundland, which had once been thought virtually inexhaustible.

“Here we are decades after that catastrophic event, and that marine ecosystem has not recovered,” Dr. Mallory said. “It’s entirely conceivable to me that we are witnessing the early stages of a similar effect, caused by a different catastrophe, in these Alaskan waters.”

Catrin Einhorn covers biodiversity, climate and the environment for The Times. More about Catrin Einhorn

 

O vilarejo no Alasca que desaparecerá sob a água 29

Quase ninguém nos Estados Unidos ouviu falar da vila de Kivalina, no Alasca. Ela fica presa em uma pequena faixa de areia na beira do mar de Bering, pequena demais para aparecer nos mapas do país.

O que talvez não seja tão ruim, porque dentro de uma década Kivalina deverá ficar embaixo d'água. Será lembrada --caso seja-- como o local de onde vieram os primeiros refugiados climáticos dos Estados Unidos.

Atualmente, 400 indígenas Inuit vivem nas cabines de apenas um cômodo de Kivalina. Sua sobrevivência depende da caça e da pesca.

O mar os sustentou por incontáveis gerações, mas nas últimas duas décadas o recuo dramático do gelo do Ártico os deixou vulneráveis à erosão da costa.

A camada grossa de gelo não protege mais a costa do poder destrutivo das tempestades do outono e do inverno. A faixa de areia de Kivalina foi dramaticamente reduzida.

Engenheiros do Exército americano construíram um muro ao longo da praia em 2008 para deter o avanço da água, mas a medida acabou sendo somente um paliativo

Uma tempestade feroz há dois anos forçou os moradores locais a uma evacuação de emergência. Agora, os engenheiros preveem que Kivalina será inabitável até 2025.

A história de Kivalina não é a única. Registros de temperatura mostram que a região do Ártico no Alasca está esquentando duas vezes mais rápido do que o resto dos Estados Unidos.

O recuo do gelo, o aumento do nível da água do mar e o aumento da erosão costeira fizeram com que três assentamentos Inuit enfrentem a destruição iminente e outros oito corram sérios riscos.

O problema também tem um custo alto. O governo americano diz que levar os habitantes de Kivalina para outro local custar até US$ 400 milhões (R$ 904 mil) - construir uma estrada, casas e uma escola não sai barato em uma região tão inacessível. E não há sinais de que o dinheiro virá de fundos públicos.

A líder da assembleia de Kivalina, Colleen Swan, diz que as tribos indígenas do Alasca estão pagando o preço por um problema que não criaram.

Líderes locais reclamam de falta de planos do governo para populações indígenas

"Se ainda estivermos aqui em 10 anos, ou esperamos pela enchente e morremos ou saímos e vamos para outro lugar", disse.

"O governo americano impôs esse estilo de vida ocidental a nós, nos deu seus fardos para carregar e agora espera que nós recolhamos tudo e carreguemos para outro lugar. Que tipo de governo faz isso?"

• 

Ao norte de Kivalina não há estradas, só a vasta tundra ártica do Alasca. E no ponto mais ao norte do território americano fica a cidade de Barrow - mais perto do Pólo Norte do que de Washington. É a fronteira da mudança climática.
Os moradores de Barrow são predominanetemente da tribo Inupiat - eles caçam baleias-da-groenlândia e focas para comer, mas tiveram uma série de problemas esse ano.
O gelo começou a derreter e quebrar em março. Depois ele congelou novamente, mas estava tão fino e instável que os caçadores de baleias e focas não conseguiram colocar seus barcos nele. A estação de caça foi arruinada.
 

Pela primeira vez em décadas, nenhuma baleia-da-groenlândia foi capturada em Barrow. Um dos capitais baleeiros mais experientes da cidade, Herman Ahsoak, diz que o gelo costumava ter 3 metros de espessura no inverno e agora tem pouco mais de um metro.
"Temos que nos adaptar ao que está acontecendo, se vamos continuar comendo e sobrevivendo através do mar. Mas a falta de baleias esse ano significa que o inverno será longo", diz.

Economia do petróleo

• Economia do Alasca é baseada na produção de combustíveis fósseis
  

Ao mesmo tempo em que o território ártico americano esquenta, ele continua a ser uma fonte vital dos combustíveis fósseis que são vistos pela maioria dos cientistas como um dos principais motivos da mudança climática.
A Encosta Norte do Alasca é o maior campo de petróleo dos Estados Unidos e o oleoduto Trans Alasca é um dos principais projetos do plano de segurança energética do país. E na medida em que a produção do campo atual diminui, aumenta a pressão para explorar reservas intocadas na região.
A empresa Shell fez um lance ambicioso para começar a explorar petróleo no oceano Ártico, apesar de um coro de desaprovação de grupos ambientais. A preocupação aumentou quando uma perfuradora de petróleo se soltou do barco ao qual estava presa na costa do Alasca no início do ano.
As operações estão suspensas, mas o valor do produto é muito alto para ser ignorado.
Kate Moriarty, diretora executiva da Federação de Petróleo e Gás do Alasca, acredita que o Estado tem cerca de 50 bilhões de barris de petróleo ainda não explorados.
"A realidade é que o Ártico vai se desenvolver. E quem queremos que lidere isso? Eu acho que queremos que sejam os Estados Unidos, porque a realidade é que a demanda mundial por petróleo e gás não vai acabar", diz.
Quando o presidente Barack Obama prometeu redobrar seus esforços para diminuir as emissões de carbono nos Estados Unidos, suas palavras foram recebidas com um mero dar de ombros no Alasca.
O Estado deve sua existência ao petróleo e os lucros da indústria de petróleo equivalem a mais de 90% do orçamento estatal. O lucro significa que não há imposto sobre a renda e que parte do dinheiro é distribuída para cada um dos moradores locais anualmente.
E quando se trata de equilibrar duas pressões conflitantes - a rápida mudança climática de um lado e a demanda para expandir a economia movida a combustíveis do outro - não há dúvidas sobre qual é a prioridade.
O vice-diretor do departamento de Recursos Naturais do Alasca, Ed Fogels, não se desculpa pela estratégia do governo. "Quando todo o mundo ataca o Alasca e diz: Ah, o clima está mudando, o Ártico está mudando, as coisas estão fora de controle', nós dizemos: 'Espere um minuto. Nós estamos desenvolvendo nossos recursos naturais há 50 anos. As coisas estão muito bem, obrigado'."
Mas dentro de uma geração, o oceano Ártico pode não ter mais gelo no verão. O ritmo do aquecimento no norte não tem paralelo em nenhum lugar do planeta.