Tag Archives: #cryosphere

Earth’s Cryosphere Shrinking by 87,000 Square Kilometers Per Year (Earth Science)

First global assessment of the extent of snow and ice cover on Earth’s surface–a critical factor cooling the planet through reflected sunlight–and its response to warming temperatures

The global cryosphere–all of the areas with frozen water on Earth–shrank by about 87,000 square kilometers (about 33,000 square miles), a area about the size of Lake Superior, per year on average, between 1979 and 2016 as a result of climate change, according to a new study. This research is the first to make a global estimate of the surface area of the Earth covered by sea ice, snow cover and frozen ground.

The extent of land covered by frozen water is just as important as its mass because the bright white surface reflects sunlight so effectively, cooling the planet. Changes in the size or location of ice and snow can alter air temperatures, change the sea level and even affect ocean currents worldwide.

The new study is published in Earth’s Future, AGU’s journal for interdisciplinary research on the past, present and future of our planet and its inhabitants.

“The cryosphere is one of the most sensitive climate indicators and the first one to demonstrate a changing world,” said first author Xiaoqing Peng, a physical geographer at Lanzhou University. “Its change in size represents a major global change, rather than a regional or local issue.”

The cryosphere holds almost three-quarters of Earth’s fresh water, and in some mountainous regions, dwindling glaciers threaten drinking water supplies. Many scientists have documented shrinking ice sheetsdwindling snow cover and loss of Arctic sea ice individually due to climate change. But no previous study has considered the entire extent of the cryosphere over Earth’s surface and its response to warming temperatures.

Contraction in space and time

Peng and his co-authors from Lanzhou University calculated the daily extent of the cryosphere and averaged those values to come up with yearly estimates. While the extent of the cryosphere grows and shrinks with the seasons, they found that the average area covered by Earth’s cryosphere has contracted overall since 1979, correlating with rising air temperatures.

The shrinkage primarily occurred in the Northern Hemisphere, with a loss of about 102,000 square kilometers (about 39,300 square miles), or about half the size of Kansas, each year. Those losses are offset slightly by growth in the Southern Hemisphere, where the cryosphere expanded by about 14,000 square kilometers (5,400 square miles) annually. This growth mainly occurred in the sea ice in the Ross Sea around Antarctica, likely due to patterns of wind and ocean currents and the addition of cold meltwater from Antarctic ice sheets.

The estimates showed that not only was the global cryosphere shrinking but that many regions remained frozen for less time. The average first day of freezing now occurs about 3.6 days later than in 1979, and the ice thaws about 5.7 days earlier.

“This kind of analysis is a nice idea for a global index or indicator of climate change,” said Shawn Marshall, a glaciologist at the University of Calgary, who was not involved in the study. He thinks that a natural next step would be to use these data to examine when ice and snow cover give Earth its peak brightness, to see how changes in albedo impact the climate on a seasonal or monthly basis and how this is changing over time.

To compile their global estimate of the extent of the cryosphere, the authors divided up the planet’s surface into a grid system. They used existing data sets of global sea ice extent, snow cover and frozen soil to classify each cell in the grid as part of the cryosphere if it contained at least one of the three components. Then they estimated the extent of the cryosphere on a daily, monthly and yearly basis and examined how it changed over the 37 years of their study.

The authors say that the global dataset can now be used to further probe the impact of climate change on the cryosphere, and how these changes impact ecosystems, carbon exchange and the timing of plant and animal life cycles.

Notes for Journalists:

Earth’s Future is an open access journal. Download a PDF copy of the paper here. Neither the paper nor this press release is under embargo.

Paper title:

“A Holistic Assessment of 1979-2016 Global Cryospheric Extent”

Authors:

  • Xiaoqing Peng, Tingjun Zhang (corresponding author), Ran Du, Haodong Jin, and Cuicui Mu (corresponding author), Key Laboratory of Western China’s Environmental Systems (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou University, Lanzhou, 730000 China
  • Oliver W. Frauenfeld, Department of Geography, Texas A&M University, College Station, TX, 77843-3147 USA

Featured image: The percentage of each area that experiences ice, snow or frozen ground at some point during the year (1981-2010). © Peng et al. (2021) Earth’s Future https://doi.org/10.1029/2020EF001969


Provided by AGU

Climate Warming Increases Cryospheric Hazards (Earth Science)

The cryosphere is an important component of the global climate system. In a narrow sense, it mainly refers the glaciers, permafrost, snow cover, and sea ice because these components are continuously distributed below the freezing point with a certain thickness. Cryospheric components are sensitive to climate warming, and changes in the cryosphere can lead to serious hazards to human society.

Fig.1. Number of publications mentioning glacial hazards (Web of Science, data from 1990 to October 2020). The red dashed lines indicate the high altitudes where land cryosphere widely distributed. The red triangle indicates the Kilimanjaro Mountain in Africa. (Image by DING Yongjian)

Recently, researchers led by Prof. DING Yongjian from the Northwest Institute of Eco-Environment and Resources (NIEER) of the Chinese Academy of Sciences (CAS) comprehensively analyzed hazards related to the atmospheric, oceanic and land cryosphere and their phenomena, mechanisms and impacts. They also evaluated the future trends of the risks of cryospheric hazards.  

In this study, the researchers found that the recorded frost hazards show a decreasing trend, and the hail hazards distribution showed great heterogeneities in the frequency and magnitude. The frequency of freezing rain events may decrease in the future, but the changes in ice load, duration of freezing rain events remains poorly understood. The probability of cold heavy snowfall, ice storms, and blizzards may increase during the weak polar vortex events.

Therefore, it’s getting more and more difficult to predict hazards from the atmospheric cryosphere in the future, while property loss is expected to increase due to the increases in population density and wealth.

Fig. 2. Process and effects of the Zhuonai Lake (a lake in lowland terrain) outbursts on environment and engineering on the Qinghai-Tibetan Plateau (Image by DING Yongjian)

For the hazards from the oceanic cryosphere, they found that the sea ice extent is declining rapidly, making it possible for the human activities extend further into high latitude areas. The iceberg numbers will likely increase, which will increase icebergs hazards.

Besides, climate change also accelerates the erosion of permafrost-dominated coastlines. Due to the rapid melting of mountain glaciers and ice sheets, the sea level rise is expected to continue in the next decades and will cause threats to low coastal lands.  

The hazards from glaciers attracted many attentions. The glacier collapse, glacial lake outburst, and dynamics in recently deglaciated environments will increase in the future because of the melting of the glacier. Although the total area of snow cover shows a decreasing trend with the warming climate, the heavy snow events, snow avalanches, and snowmelt floods will not decrease simultaneously because snowfall has large spatial heterogeneities. The permafrost-related rock and debris flow and thaw slump will increase with permafrost degradation.

Graphical abstract by Ding et al.

In addition, permafrost-dammed lakes in low terrains also at the risk of outbursts due to the rapid thaw of permafrost.  

“It is clear the cryosphere is shrinking, while cryospheric hazards will likely increase in the future,” said DING Yongjian, “although the cryospheric hazards remain highly uncertain, climate change and destabilization of the cryosphere will exacerbate our social and economic risks. Therefore, the prediction and warning of the hazards are important to minimize harm for human society.”

This work has been published on Earth-Science Reviews recently titled “Increasing cryospheric hazards in a warming climate“. 

Reference: Yongjian Ding, Cuicui Mu, Tonghua Wu, Guojie Hu, Defu Zou, Dong Wang, Wangping Li, Xiaodong Wu, Increasing cryospheric hazards in a warming climate, Earth-Science Reviews, Volume 213, 2021, 103500, ISSN 0012-8252, https://doi.org/10.1016/j.earscirev.2020.103500. (http://www.sciencedirect.com/science/article/pii/S0012825220305468)

Provided by Chinese Academy of Sciences