A Holistic Assessment of 1979–2016 Global Cryospheric Extent. Issue 8 (5th August 2021)

• Record Type: Journal Article
• Authors: Peng, Xiaoqing; Zhang, Tingjun; Frauenfeld, Oliver W.; Du, Ran; Jin, Haodong; Mu, Cuicui
• Is Part Of: Earth's future. Volume 9:Issue 8(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-08-05
• Subjects: climate -- cryosphere; Environmental sciences -- Periodicals; Environmental sciences; Periodicals; 550
• DOI: 10.1029/2020EF001969
• Languages: English
• ISSNs: 2328-4277

Abstract

Abstract: The cryosphere plays a major role in earth's climate system. Most cryospheric assessments focus on one or more of its components and their response to climate change. However, to date, there has not been a comprehensive evaluation of the entire global cryosphere. We therefore determine such a holistic estimate and quantify changes to the hemispheric and global cryosphere due to climate change, by synthesizing sea ice, snow cover, and frozen ground extents into one global cryospheric extent data set. The 1981–2010 climatology of daily global cryospheric extent ranges from 45.7 ± 0.7 × 10 6 to 87.2 ± 2.0 × 10 6 km 2 (9.0%–17.1%), from 13.3 ± 0.8 × 10 6 –66.3 ± 1.7 × 10 6 km 2 (5.2%–26.0%) in the Northern Hemisphere (NH), and from 17.9 ± 0.3 × 10 6 to 33.6 ± 0.4 × 10 6 km 2 (7.0%–13.2%) in the Southern Hemisphere (SH). The monthly maximum cryospheric extent of 85.84 ± 1.91 × 10 6 km 2 occurs in December, whereas minimum occurs in July with 45.92 ± 0.70 × 10 6 km 2 . During 1979–2016, global cryospheric area extent lost approximately 87 ± 11 × 10 3 km 2 /yr, with a decrease of 102 ± 9.7 × 10 3 km 2 /yr in the NH that was partly offset by an increase of 14.6 ± 4.4 × 10 3 km 2 /yr in the SH. The first day of cryospheric cover was delayed by 3.6 days at a rate of 0.95 days/decade, and the last day advanced by 5.7 days, at a rate of 1.5 days/decade. The duration and number of cryospheric cover days decreased by 8.7 days and 7.6 days over the study period, respectively. These variations of global cryospheric extent are correlated with rising air temperatures. Our findings highlight the importance of assessing the cryosphere as a whole, and provide a way to quantitatively estimate its overall changes. Plain Language Summary: The cryosphere is an important part of the earth's interconnected climate system. Most research about the cryosphere focuses on individual elements. However, no study so far has looked at how "the cryosphere" as a whole has changed over time. We therefore combine the global area of sea ice, snow cover, and frozen ground to estimate how all of earth's frozen parts have been changing. This global cryospheric area, over a 30‐year climatology (from 1981–2010), varies from 46, 000, 000 to 87, 000, 000 km 2 (9–17%). Of this global cryospheric area, 13, 000, 000–66, 000, 000 km 2 (5–26%) are found in the Northern Hemisphere (NH), and 18, 000, 000 to 34, 000, 000 km 2 (7–13%) in the Southern Hemisphere (SH). The biggest cryospheric extent (86, 000, 000 km 2 ) is in December, and the smallest in July (46, 000, 000 km 2 ). During the years 1979–2016, the global cryosphere shrunk by 87, 000 km 2 each year, with a big decrease of 102, 000 km 2 every year in the NH that was compensated for by a small increase of 15, 000 km 2 every year in the SH. The first day when the seasonal cryosphere forms is now 3.6 days earlier, and the last day is 5.7 days later. Together, this means there are now approximately 8 fewer days that the earth is frozen. Key Points: Holistic changes in global cryospheric extent have not previously been quantified Each year, global cryospheric area extent decreased 87 ± 11 × 10 3 km 2 Climate change resulted in a decline of the duration and number of cryospheric cover by two or more days/decade