The formation of glaciers goes through three stages: sufficient atmospheric solid precipitation forms a snow layer, the snow turns into firn through rounding, and the firn then forms glacial ice through metamorphism. A glacier is formed by the gradual deposition of layers of ice, each reflecting a specific geological period and a particular geographical and climatic environment. During the long formation process, glaciers are constantly changing, mainly in two aspects: first, they accumulate and ablate under the influence of climate change; second, under the action of gravity, they undergo plastic deformation and basal sliding, moving at a speed of tens of meters, hundreds of meters, or even thousands of meters per year. During these movements, glaciers erode, transport, and deposit materials. Recently, the 2024 Ice Peak Conference and Youth Scientific Exploration Activity was launched in Sichuan. The theme of the activity is "From Science to Society: Cryosphere Retreat on the Qinghai-Tibet Plateau and Climate Change Response". With global warming, in the Qinghai-Tibet Plateau, known as the "Third Pole of the Earth", and the surrounding alpine regions, while the area of glaciers is constantly shrinking, the thickness of glaciers is also thinning. So, how thick are glaciers? How much have they thinned? How to measure glacier thickness? With these questions, a reporter from Science and Technology Daily interviewed relevant experts. Thickness data has important value Ocean water on Earth accounts for about 96.5% of the total global water volume, while freshwater accounts for only 2.53%, of which three-quarters is stored in the Antarctic ice sheet, Greenland ice sheet, and mountain glaciers. According to the data of the second Chinese Glacier Inventory, there are 48,571 glaciers in China, with a total area of 51,766.08 square kilometers, accounting for about 7.1% of the world's glacier area (excluding the Antarctic and Greenland ice sheets). "Glaciers have important scientific and application value in the fields of climate change, water resource management, sea level rise, ecological protection, economic and social development," said He Xiaobo, associate researcher at the Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences. In the past century, due to the warming of the global climate system, the melting of glaciers and snow has accelerated. Changes in glaciers affect the water cycle in surrounding areas, thereby affecting the ecology and environment of river source regions. "In recent years, the thinning and retreat of mountain glaciers are responses to climate warming, reflecting the sensitivity of glaciers to climate change," He Xiaobo said. Glacier thickness, subglacial topography, and glacier volume are three important basic parameters of glacier change, and also the basic data for research and evaluation work such as glacial water resources, glacier surges, and ice core drilling, which are related to glacier storage, glacier movement, and internal glacier structure. Through ice surface topography and ice thickness measurement data, researchers can map subglacial topography and estimate glacier volume, thereby obtaining information on glacial water resource reserves. He Xiaobo said: "Glacier thickness measurement data can provide the thickness value of glacier measurement points and the average thickness of the entire glacier, based on which researchers can draw topographic maps under glaciers and accurately estimate glacier volume." Monitoring glacier conditions and carrying out systematic research on glacier changes have important scientific significance and high application value. Developing measurement "tools" Historically, on-site coring, gravity method, and seismic wave method have been commonly used for glacier detection. However, these methods are characterized by high work intensity, low efficiency, and poor safety. The Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, has innovated glacier detection methods, making the measurement more accurate. The institute used China's independently developed integrated radar for ice and water conditions to conduct a comprehensive detection of the thickness of the East Rongbuk Glacier on Mount Qomolangma, and successfully obtained the glacier thickness data in the range of 6,300 meters to 6,500 meters above sea level of the East Rongbuk Glacier. The radar used is a ground-penetrating radar that can penetrate specific media such as ice and snow. It is an electronic device that uses the characteristics of electromagnetic waves reflected by targets such as subglacial bedrock, internal ice cavities, and medial moraines to detect targets and determine their distance and direction. He Xiaobo said, simply put, it is based on the difference in dielectric constants between ice-water and bedrock, and determines the target position through changes in the transmission speed of radio waves in the ice body. In general, the structural changes of subglacial media are relatively slow, and the electrical properties of the same ice layer are relatively similar. Therefore, when using ground-penetrating radar for continuous measurement, the main characteristics such as waveform, amplitude, period, and envelope of the reflected wave from the same stratum at adjacent measuring points have certain similarities. Reflected waves with certain morphological characteristics are the basis for identifying reflective layers, while the in-phase and similarity of reflected waves from the same stratum provide a basis for tracking reflective layers. In the past, ice radar data analysis usually used manual methods to extract horizons, which required finding local continuity and similarity characteristics in the data to identify the event horizons to be extracted. This method has slow interpretation speed, low accuracy in event horizon tracking, and weak jumps. To solve this problem, the integrated radar system for ice and water conditions used by He Xiaobo's team innovatively loaded a new algorithm combining amplitude and local gradient, making it possible to conduct cross-validation based on both single observation point data and adjacent time series. The algorithm simultaneously achieves accurate measurement of water depth and ice thickness, and also makes the previously complex horizon information presented in a clearer and more intuitive way. After analysis and testing, the research team determined radars with two frequencies: 100 MHz and 400 MHz, which can measure water depth and ice thickness with high precision. The research team also improved the shape and arrangement of radar antennas, so that the measuring points for shallow ice structure and ice thickness of water depth are on the same vertical line, and avoided mutual interference between radars of different frequencies through time-sharing work. Wang Shaoyong, a doctoral student at the Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, introduced that more than a decade ago, a scientific expedition team measured the thickness of the East Rongbuk Glacier, and the data showed that the maximum thickness of the East Rongbuk Glacier at an altitude of 6,300 meters reached 320 meters. "This time, we used the newly developed instruments to more accurately obtain glacier thickness data. By comparing with previous measurement data, we can further understand the changes in the thickness of the East Rongbuk Glacier in the past decade or so," Wang Shaoyong said. Preliminary data processing found that the maximum thickness of the East Rongbuk Glacier is more than 300 meters. Based on the thickness data of the East Rongbuk Glacier, the ice storage of the East Rongbuk Glacier can be accurately estimated, and the water resources contained in the glacier can be further explored, providing data support for agricultural and animal husbandry development and water resource management in the downstream of the glacier. Expected to realize "perspective" of the Earth "The integrated radar for ice and water conditions, which we jointly developed with the China Institute of Water Resources and Hydropower Research, Dalian Zhongrui Technology Development Co., Ltd., etc., is based on the principle of ultra-wideband impulse radar technology, realizing high-resolution penetration imaging measurement of glacier bodies, their internal structures, and basement topography," He Xiaobo said. The innovations and technological breakthroughs of this achievement in high-power and high-signal-to-noise ratio antenna technology, ultra-deep radar signal acquisition and processing technology, and high-quality radar data processing algorithms have made China's glacier radar measurement technology and special equipment reach the international advanced level. The reporter learned that because He Xiaobo's team adopted the latest advanced radar detection and measurement technology, the data measurement accuracy has been directly improved by an order of magnitude, and the data quality, representativeness, and reliability have been significantly improved. The absolute error of the developed equipment is about 5% of the measured ice thickness value. At the same time, the existing glacier storage estimation formula will also be targeted and optimized based on the accurate measurement data of glacier thickness by radar. In the future, China will carry out thickness measurement of representative glaciers in different regions, types, and scales, evaluate and improve the existing glacier radar measurement accuracy and algorithms, collect global mountain glacier thickness measurement data, and improve and optimize storage calculation formulas suitable for glaciers of different scales. "The integrated radar for ice and water conditions and the data and information obtained through this advanced technical means allow us to 'perspective' the Earth. In the future, this radar will have broad application prospects in China's glacier survey and measurement, environmental and climate surveys, permafrost zones and permafrost zone engineering surveys, river, lake, and reservoir ice engineering surveys, ice and water condition observation and measurement, polar scientific expeditions and other fields," He Xiaobo introduced. Extended knowledge: Thickness distribution of glaciers in the world The size and shape of glaciers and ice sheets are controlled by atmospheric and oceanic changes. Their current shrinkage provides direct and clear evidence of global climate change. Since they provide freshwater resources for local populations and currently contribute 25-30% to sea level rise, which threatens about 10% of the world's population living below 10 meters above sea level, modeling their future evolution has become crucial. Despite international efforts over the past few decades that have significantly improved the representation of ice masses, the thickness distribution of the world's glaciers remains highly uncertain. Only 4,700 of the world's 215,000 glaciers have on-site measurements of ice thickness, and most of these glaciers only cover part of the glacier. Several model-based global glacier thickness reconstructions have been proposed, and estimates within the Randolph Glacier Inventory (RGI) regions vary widely depending on the model used, highlighting the lack of confidence in these models. In fact, current ice thickness models mostly use simplified glacier geometries based on width-averaged centerline methods, which are applied glacier by glacier (relying on glacier basin boundaries) and make strong assumptions about basal shear stress or surface mass balance gradients. While these methods may be reasonable for valley glaciers, they result in unrealistic bedrock geometries for ice caps and tidewater glaciers, where most of the global ice volume outside Greenland and Antarctica is located. This inconsistency in glacier thickness needs to be addressed because it has been shown that ice thickness distribution has a greater impact than total ice volume in predictions of glacier evolution over the next few decades. In other words, obtaining the correct global ice volume does not help in simulating the future of glaciers if the thickness distribution of glaciers is not properly captured. The impact of climate change on water resources and sea level rise largely depends on the size and thickness distribution of ice reservoirs around the world, but they are still uncertain. Here, we present a comprehensive high-resolution map - a map of ice motion for 98% of the global glacier area between 2017 and 2018. We use this glacier flow map to estimate global ice volume, thereby reconciling ice thickness distribution with glacier dynamics and surface topography. The results show that the potential contribution of the world's glaciers to sea level rise is 257 ± 85 mm, 20% lower than previous estimates. In low latitudes, our findings highlight significant changes in freshwater resources, with a 37% increase in ice in the Himalayas and a 27% decrease in ice in the tropical Andes of South America, affecting water availability for local populations. This mapping of glacier flow and thickness redefines our understanding of global glacier volume distribution and has implications for predictions of glacier evolution worldwide, as accurate representation of glacier geometry and dynamics is crucial for glacier modeling. Article sources: Science and Technology Daily, Geographic Window, Development Geography