ESA’s (European Space Agency) Copernicus Sentinel-2 mission explored Alaska’s Columbia Glacier, one of the fastest-changing glaciers in the world. The Columbia Glacier is a tidal glacier flowing down the snow-covered slopes of the Chugach Mountains. The mountains contain the largest concentration of glacial ice in Alaska. Since the early 1980s, the Columbia Glacier has retreated more than 20 km and lost about half of its total volume. This glacier accounts for nearly half of the ice lost in the Chugach Mountains.
Climate change is believed to be the reason for its retreat. Until 1980, when its rapid and steady retreat began, the glacier’s terminus was observed at the northern edge of Heather Island, which lies near the end of Columbia Sound, the bay into which the glacier currently flows before emptying into Prince William Sound.
New satellite images taken in September 2023 instead show a deep, nearly ice-free Columbia Bay littered with numerous icebergs and fragmented sea ice. Depending on the amount of sediment coming from the Chugach Mountains, bodies of water throughout the image can be seen in different colors: the clear waters of the Pacific Ocean appear dark blue, and the murky waters of bays and glacial lakes appear blue or light blue.
The Columbia is just one of many glaciers suffering from the effects of climate change. Most glaciers around the world are losing mass. However, before the advent of satellites, measuring their distance and studying their vulnerability to climate change was difficult, given their size, remoteness and the rugged terrain they occupy. Various satellite instruments can now collect information systematically and over large areas, providing an effective means to monitor changes, track all stages of calving, and quantify melt rates and their contribution to sea level rise.
An abnormally high temperature was also recorded in Alaska near the city of Utqiagvik, The Washington Post reports. It is one of the northernmost cities in the world and the northernmost populated area in the United States. On December 5, 2023, the thermometer rose to +4.4 °C, which became the highest temperature between November and March for this place in the entire history of meteorological observations, which goes back more than 100 years. This is almost 20 degrees more than normal for this time of year. The previous record was recorded in December 1932, when the temperature in the Utqiagvik region rose to +1.1 °C.
Underwater glaciers in Alaska are melting 100 times faster than previously thought. Oceanographer Dave Sutherland of the University of Oregon and his colleagues studied the underwater melting of the Leconte Glacier, located south of Juneau in Alaska. To map the glacier’s underwater edge, the team used multibeam scanning sonar deployed on a fishing vessel in August 2016 and May 2017. The researchers also collected data on temperature, salinity and water velocity downstream of the glacier to estimate meltwater flow. From this, the team was able to look at dynamic changes in the melts between August and May.
Although glaciers rise above the ocean, most of the melting occurs below the sea line. Water on the surface of the glacier flows down through cracks in the ice, creating a flow beneath the glacier, which also destroys the glacier. It mixes salty, relatively warm seawater and pushes it up the surface of the glacier, causing the ice to melt quickly.
In general, the temperature of the World Ocean is setting records at an increasing rate. But scientists are worried not only about the record temperature itself, but also about the speed at which the ocean is warming. As you know, seas and oceans stabilize the climate on the planet. Scientists estimate that about 91% of excess heat trapped by greenhouse gases and 31% of human CO2 emissions accumulate in the oceans, protecting humanity from even faster climate change. That is, the ocean is holding back global atmospheric warming, but at the same time its own temperature is rising faster and faster.