The ice that held it had to vanish, and it did—in just forty years.
En las montañas del sureste de Alaska, el tiempo ha desenterrado lo que el hielo mantuvo oculto durante siglos: una cima llamada Prow Knob, bautizada por un glaciólogo en los años sesenta por su parecido con la proa de un barco, es hoy una isla completa rodeada de agua. Imágenes satelitales de la NASA documentan cómo el glaciar Alsek ha retrocedido más de cinco kilómetros desde los años ochenta, convirtiendo un lago de 45 kilómetros cuadrados en uno de más de 75. Lo que emerge no es solo tierra: es la huella visible de un planeta que se transforma a un ritmo que ya no puede ignorarse.
- El glaciar Alsek ha retrocedido más de cinco kilómetros en cuatro décadas, un ritmo que ha acelerado hasta hacer desaparecer el contacto entre el hielo y la montaña que alguna vez abrazaba.
- Alsek Lake ha crecido más de un 60 por ciento en una sola generación, una expansión que no es anomalía sino consecuencia directa de que el hielo se derrite más rápido de lo que se repone.
- El patrón no es aislado: los lagos Harlequin y Grand Plateau muestran la misma duplicación de superficie, señalando una pérdida sistemática de masa glaciar en toda la región.
- Cuando los glaciares pierden contacto con el lecho rocoso que los ancla, se vuelven inestables y más propensos al colapso, amplificando el riesgo de una disintegración acelerada.
- El agua liberada por estos glaciares fluye hacia el océano, y la pregunta que inquieta a los científicos del clima es cuánto de ese flujo terminará elevando los niveles del mar a escala global.
Bajo las montañas del sureste de Alaska, algo que había permanecido atrapado en el hielo durante siglos acaba de quedar libre. La NASA ha confirmado que Prow Knob, una cima que el glaciólogo Austin Post avistó desde el aire en los años sesenta y bautizó por su parecido con la proa de un barco, es hoy una isla completa. El hielo que la rodeaba ha desaparecido. El agua la rodea por completo.
El glaciar Alsek ha retrocedido más de cinco kilómetros desde mediados de los años ochenta, según el glaciólogo Mauri Pelto, de Nichols College, quien ha seguido estos cambios de cerca. Las imágenes de los satélites Landsat 5 y Landsat 9 documentan esa transformación con precisión: el lago Alsek pasó de cubrir unos 45 kilómetros cuadrados en los ochenta a más de 75 en la actualidad, un crecimiento de más del 60 por ciento en una sola generación. El lago no creció por azar. Creció porque el hielo se derrite más rápido de lo que se repone, y el agua tiene que ir a algún lugar.
Lo que hace significativa a Prow Knob no es su singularidad, sino precisamente lo contrario. La NASA ha identificado el mismo patrón en otros lagos proglaciares de la región, como Harlequin Lake y Grand Plateau Lake, todos aproximadamente duplicados en tamaño durante las últimas cuatro décadas. Cuando los glaciares pierden contacto con las montañas y el lecho rocoso que los anclan, se vuelven inestables, más vulnerables al colapso y a la desintegración rápida.
Las consecuencias van más allá de la imagen de una montaña convertida en isla. El agua que liberan estos glaciares fluye hacia el océano, y si el retroceso continúa a este ritmo, el efecto acumulado sobre los niveles del mar podría ser considerable. Prow Knob es un marcador visible de un proceso que está redibujando el Ártico, con consecuencias que se sentirán mucho más allá de las costas de Alaska.
Beneath the mountains of southeastern Alaska, something that had been locked in ice for centuries has broken free. NASA satellites have now confirmed what was once a peak buried under the Alsek Glacier—a formation called Prow Knob—has become a full island, surrounded entirely by water. The transformation, captured in satellite imagery spanning from 1984 to 2025, tells a story written in the retreat of glacial ice across four decades.
Prow Knob sits in Alsek Lake, a body of water fed by the glaciers that dominate the coastal landscape of southern Alaska. The mountain itself has a history. In the 1960s, a glaciologist named Austin Post spotted it from the air and named it for its resemblance to a ship's bow. For generations after that, it remained what it appeared to be: a peak surrounded by ice. But the ice has been moving, slowly at first, then with accelerating speed. The Alsek Glacier has retreated more than five kilometers since the middle of the 1980s, according to Mauri Pelto, a glaciologist at Nichols College who has tracked these changes closely. That retreat has been relentless enough that by 2025, the mountain no longer touches ice at all. Water surrounds it completely. It is now, officially, an island.
The lake itself has grown dramatically. In the 1980s, Alsek Lake covered roughly 45 square kilometers. Today it spans more than 75 square kilometers—an expansion of more than 60 percent in a single generation. NASA's Earth Observatory documented this shift using data from the Landsat 5 and Landsat 9 satellites, instruments that have been watching this corner of Alaska long enough to see the ice vanish. The growth of the lake is not incidental. It is a direct consequence of the glaciers melting faster than they can be replenished. More ice turns to water. The water has to go somewhere. It fills the basin where the glacier once was.
What makes Prow Knob significant is not that it is the only place this is happening. NASA has identified the same pattern repeating across other proglacial lakes in the region—Harlequin Lake and Grand Plateau Lake among them. These bodies of water have all roughly doubled in size over the past four decades. The pattern suggests something larger at work: a systematic loss of glacial mass across an entire region. When glaciers lose contact with the natural anchors that hold them in place—the mountains and bedrock beneath them—they become unstable. Without those fixed points, the ice becomes more vulnerable to collapse, more prone to rapid disintegration.
The implications extend beyond the visual drama of a mountain becoming an island. As glaciers shrink and lose their grip on the landscape, they release water that flows downhill. Some of that water feeds into the ocean. The question that haunts climate scientists is how much. If the glaciers of Alaska continue to retreat at their current pace, if this pattern spreads and accelerates, the cumulative effect on sea levels could be substantial. The emergence of Prow Knob is not just a curiosity. It is a visible marker of a process that is reshaping the Arctic, one that will have consequences far beyond Alaska's shores.
Citas Notables
In the 1960s, glaciologist Austin Post observed the formation from the air and named it for its resemblance to a ship's bow— National Geographic reporting on Prow Knob's naming
The Alsek Glacier has retreated more than 5 kilometers since the mid-1980s, illustrating the tangible loss of glacial mass in the region— Mauri Pelto, glaciologist at Nichols College
La Conversación del Hearth Otra perspectiva de la historia
Why does a mountain becoming an island matter so much? It's one piece of rock in a vast landscape.
Because it's not really about the rock. It's about what had to happen for that rock to become an island. The ice that held it had to vanish. And the ice didn't vanish slowly or evenly—it retreated five kilometers in forty years. That's the signal.
But couldn't that just be a local fluctuation? Glaciers advance and retreat naturally.
They do, over centuries or millennia. This is different in speed. And it's not isolated. The same thing is happening in lake after lake across the region. When you see the same pattern repeating, it stops being a local story.
What happens to all that water? Where does it go?
Into the ocean, eventually. Some of it stays in the lakes—that's why Alsek Lake grew by 30 square kilometers. But the rest flows downhill. Multiply that across all the glaciers in Alaska, then Greenland, then Antarctica, and you're talking about sea level rise that affects coastlines everywhere.
So this island is a warning sign.
It's more than that. It's evidence. Prow Knob is proof that the ice is leaving. You can see it in the satellite photos. You can measure it. It's not a projection or a model—it's something that already happened.