Glaciers around the world are melting, all at different speeds. In this week’s Video of the Week, check out how scientists are using the sounds from melting Arctic glaciers to assess the speed of glacier melting.
The sounds are produced by air bubbles that become trapped when snow turns to ice over time. When the ice melts, the bubbles pop in the water producing a sound that can help show how fast a glacier is melting. By using acoustical recordings, scientists hope to improve our understanding of how sea levels may rise in the future. The video was published by the American Geophysical Union. In addition to this video, check out GlacierHub’s article on the paper behind the video.
This week marked the annual meeting of the American Geophysical Union (AGU), the world’s largest organization of Earth and space scientists. It brought together over 24,000 of the brightest scientific minds in New Orleans, Louisiana, to discuss groundbreaking research from every field and opportunities for a more sustainable future. Unsurprisingly, glaciers played a prominent role at the meeting, including during their own glaciology poster presentation.
This Photo Friday, enjoy some of the photos from #AGU17.
The Kunlun Mountains, featured as a mythical location in the legendary Chinese text Shanhai Jing, are one of the longest mountain chains in Asia. From the Pamirs of Tajikistan, the mountains run east along the border of Xinjiang and Tibet to the Qinghai province, forming part of the Tibetan Plateau. A number of important glaciers and lakes are found in the area, attracting glaciology researchers to the region throughout the year. Yanbin Lei, an associate research fellow at the Chinese Academy of Sciences, is one scientist conducting important field work in the region.
Recently, Lei et al. published a paper in the American Geophysical Union Journal Geophysical Research Letters that describes how lakes in the Tibetan Plateau are growing and deepening due to climate change. In particular, the scientists identified two patterns of lake level seasonality.
Because the climate is warming, an earlier melt and a relatively large increase in spring runoff are observed for all scenarios. This in turn increases water availability in the Indus Basin irrigation scheme during the spring growing season, according to Lei et al. This finding projects that rainfall will increase, according to another study by Su er al. In addition, the discharge in the major large rivers of South and East Asia will also increase.
“Though crucial, the paucity of instrumental data from the sparsely populated Tibetan Plateau has limited scientific investigations of hydroclimate response to recent climate change,” Lei told GlacierHub. The Tibetan Plateau has a large spatial coverage and high elevation (the average latitude is over 4000 meters), not to mention an incredibly harsh climatic condition, which makes conducting research and taking measurements difficult. Because the seasonal dynamics of the lakes is not sufficiently understood, the research conducted by Lei et al. in the Tibetan Plateau was unprecedented.
“In general, there is a lack of monitoring of lake levels in the Kunlun Mountains, and consequently, data is missing for the lakes,” Lei added. “Even if remote sensing were developed as a major method for studying inter-annual changes of lakes, the accuracy and frequency of this method would still be limited to study seasonal changes.”
With the help of “situ observations,” Cryosat-2 satellite altimetry data between 2010 and 2014, and Gravity Recovery and Climate Experiment (GRACE) data, Lei et al. managed to identify two patterns of lake level seasonality. “In the central, northern, and northeastern Tibetan Plateau, lake levels are characterized by considerable increases during warm seasons and decreases during cold seasons, which is consistent with regional mass changes related to monsoon precipitation and evaporation,” Lei et al. describe in their paper. “In the northwestern Tibetan Plateau, however, lake levels exhibit dramatic increases during both warm and cold seasons, which deviate from regional mass changes.”
In an interview with GlacierHub, Lei summarized the reasons for this finding: “The difference was mainly caused by the glaciers and precipitation. There are widespread glaciers in the northwest Tibetan Plateau and the area of glaciers is larger than the area of lakes. The precipitation in summer is also low, resulting in high spring snowfall and large summer glacier melt to feed the lake. Meanwhile, in the northern Tibetan Plateau, there are fewer glaciers but more summer rainfall, causing an increase in the lake level,” Lei told GlacierHub.
Additionally, the seasonal difference of precipitation is also important. Annual precipitation in the northern Tibetan Plateau is 300-400 mm with 90 percent of precipitation occurring in summer, according to Lei. Annual precipitation in the northwest Tibetan Plateau is about 200 mm because spring snowfall counts more. “The lake level responses to different drivers indicates heterogeneous sensitivity to climate change between the northwestern Tibetan Plateau and other regions,” Lei noted.
As Lei et al. demonstrate in their study, climate change has dramatically influenced the lakes and rivers of Tibet. Higher temperatures saliently have led to the expansion of the watershed. However, Lei is unsure about the exact effect of climate change.
“Since 2006, lakes in the central Tibetan Plateau have been stable, while lakes in the northern Tibetan Plateau and Northwest Tibetan Plateau are growing at a high speed,” he said. “When these lakes will reach equilibrium remains uncertain.”
Alaska’s impact on global sea level rise is becoming more pronounced. Its melting glaciers, particularly the minority mountain glaciers, will be a major driver of sea level change in the coming decades, according to a new study conducted by Chris Larsen, research associate professor at the University of Alaska Fairbanks, and his colleagues.
With over 100,000 glaciers, Alaska is home to half of the world’s glaciers. Every seven years, glacier loss from Alaska contributes a 1-foot thick layer of water covering the state of Alaska. Though mountain glaciers hold less than 1% of the total glacier volume on the Earth, the recession of mountain glaciers contribute to nearly 1/3 of current sea level rise.
Larsen and his team examined 116 glaciers across Alaska to estimate ice loss from melting and iceberg calving between 1994 to 2013. Iceberg calving, the unique process of ice chunks breaking off at the edge of a glacier, is underlined in the study because few existing observations or models value the impact of iceberg calving under climate change.
“We’ve long wondered what the contribution of iceberg calving could be across the entire state,” O’Neel, one of the researches, told the American Geophysical Union. The Columbia Glacier in Prince William Sound has retreated more than 12 miles mostly due to iceberg calving since 1980.
The University of Alaska Fairbanks collected airborne lidar altimetry data, highly specialized research aircrafts, as part of NASA’s Operation IceBridge mission since 2009. The mission aims to picture the Earth’s polar ice in unprecedented detail with innovative science instruments to better connect the polar regions with the global climate system.
The team also integrated the new data with information from the 1990s collected by the University scientists and Keith Echelmeyer, a pilot, mountaineer and pioneer glaciologist. They developed a more detailed characterization of the size and shape of every glacier in Alaska, in addition to the glaciers of southwest Yukon Territory and coastal northern British Columbia.
With the new data inventory, the research team has made some significant discoveries. Across the years from 1994 to 2013, Alaska’s tidewater glaciers contributed to only 6% of Alaska’s mass loss. Glaciers that end in the ocean, called tidewater glaciers, make minimal contribution to sea level rise, while glaciers ending on land are primary contributors to mountain glacier mass loss driven by climate change.
“This work has important implications for global sea level projections. With improved understanding of the processes responsible for Alaska glacier changes, models of the future response of these glaciers to climate can be improved,” Larsen told the American Geophysical Union. Despite the fact that the impact of the large-scale tidewater glacier losses in Alaska is negligible, Alaska will remain a major contributor to global sea level rise through its mountain glaciers.