Aug 18 2020
A new study has analyzed nearly 30 years of scientific data related to the melting of the Greenland Ice Sheet. The analysis points toward a possible global sea level rise of at least 10 cm by the end of the 21st century if global warming were to continue at the current trend.
Iceberg off Ammassalik Island, southeast Greenland. Image Credit: Professor Edward Hanna.
The researchers warn that the estimates, which are largely in agreement with recent estimates reported by the Intergovernmental Panel on Climate Change, are “conservative” due to the strong impacts of changes in weather systems and potential ways in which ice loss is accelerated.
Led by Professor Edward Hanna from the University of Lincoln in the United Kingdom, an international research team, including climatologists and glaciologists from Switzerland, Denmark, Belgium, and the United States, performed the new study that evaluates the response of the Greenland Ice Sheet to climate change. The study outcomes have been reported in the International Journal of Climatology.
The Greenland Ice Sheet is a huge reservoir of ice containing water sufficient to eventually increase the global sea level by 7 m.
The team offers a fresh analysis of data related to the Greenland surface air temperature for the past 30 years until 2019, where the focus of the study was not only on coastal weather stations but also on the analysis of records from comparatively long-running sites on the inner plateau of the ice sheet.
The study identified that the Greenland coastal regions warmed considerably by around 4.4 °C in winter and 1.7 °C in summer from 1991 to 2019.
The study combined Greenland temperature data with the output of the computer model of ice-sheet mass balance for 1972 to 2018 and demonstrated that every 1 °C of summer warming leads to 116 billion tons of total mass loss and 91 billion tons of surface mass loss from the ice sheet annually.
Furthermore, the researchers employed certain newly available global and regional climate modeling tools to evaluate that, under the influence of sustained strong global warming (a “business as usual” scenario), Greenland could probably warm up to 4.0 °C–6.6 °C by the year 2100.
These latest and predicted future Greenland warmings are significantly higher compared to global temperature variations for corresponding time periods, which point toward a high sensitivity of the polar regions to climate change.
The researchers then used the relation they derived between the latest variations in Greenland summer temperature and surface mass balance to estimate a 10–12.5 cm increase in global sea-level rise by 2100, caused by increased Greenland surface mass loss and ice melt.
Prof. Hanna’s research group also examined the relationship between the changes in Greenland air temperature and a phenomenon known as atmospheric high-pressure blocking, which is caused by a higher-than-normal mass of air occasionally positioned over Greenland.
Although this relation has usually existed previously, it has gained more strength in summer and spring in recent decades. The researchers demonstrate that Greenland blocking played a vital role in the near-record Greenland melt in the summer of 2019 (narrowly exceeded by the all-time record in 2012) and indicate that potential future variations in blocking must be taken into account in computer-model projections of climate change.
The Greenland Ice Sheet is one of the most sensitive and reliable measures of global climate change. Here we have used relatively simple statistical analysis of data and model output from the last 30 years as a sense-check on prediction of future ice-sheet surface mass change.
Edward Hanna, Professor, Climate Science and Meteorology, School of Geography and Lincoln Centre for Water and Planetary Health, University of Lincoln
Hanna continued, “Our work, which represents in part a major updated analysis of Greenland climate records, is highly interdisciplinary since it cross-cuts between climate science and glaciology, and so will help improve interpretation of recent ice-sheet changes.”
The authors’ group very sadly observes the passing of their co-author Professor Konrad “Koni” Steffen from the Swiss Federal Institute for Forest Snow and Landscape Research WSL, who unfortunately died in an accident in Greenland on August 8th, 2020. Prof. Steffen was a trailblazer in Greenland Ice Sheet research and an esteemed, good, loyal, and inspiring collaborator over several years. The team misses him very much.
Journal Reference:
Hanna, E., et al. (2020) Greenland surface air temperature changes from 1981 to 2019 and implications for ice-sheet melt and mass-balance change. International Journal of Climatology. doi.org/10.1002/joc.6771.