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by Hannah Chicken
, Phys.org
West Greenland Ice Sheet complete ice discharge and floor melting for April 2022 to April 2023. Credit score: Ing et al. 2024.
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West Greenland Ice Sheet complete ice discharge and floor melting for April 2022 to April 2023. Credit score: Ing et al. 2024.
Ice melting has turn out to be an ever-pressing concern in current many years as local weather change has introduced evocative photos of lone polar bears floating on unsustainable small blocks of sea ice. But, the implications are far-reaching by way of freshening of seawater altering marine ecosystems, sea degree rise exacerbating flooding and discount of ice-albedo feedbacks that additional modify Earth’s temperature.
New analysis, revealed in Geophysical Analysis Letters, has investigated the affect of late-season melting of the Greenland Ice Sheet to establish its impact on ice circulation. This displays the affect that floor melting has on modifying the ice sheet’s motion, doubtlessly transporting ice extra quickly to decrease elevations which might be hotter, thus encouraging greater soften charges.
Ryan Ing, a Ph.D. researcher on the College of Edinburgh, UK, and colleagues centered on soften occasions occurring throughout 2022, a yr that skilled seasonal air temperatures greater than beforehand recorded for the Greenland Ice Sheet within the late soften season.
Explaining the motivation behind their work, Ing stated, “Because the local weather warms, we’re noticing extra frequent durations of intense floor melting on the Greenland Ice Sheet, particularly in direction of the tip of the summer time. Throughout this time, the ice sheet’s motion turns into significantly attentive to spikes in floor melting, doubtlessly transferring extra ice to decrease elevations the place air temperatures are greater.
“Our examine centered on analyzing a number of intense melting occasions that occurred in late summer time 2022 and their impact on the annual motion of the ice sheet. Regardless of observing a big acceleration in ice movement, this acceleration was short-lived, lasting just a few days, and didn’t considerably affect the general annual movement of the ice sheet.”
“Whereas these late-summer soften occasions might not pose a significant concern for elevated ice movement, our findings spotlight their important position in intensifying floor melting on the ice sheet.”
Utilizing a document of satellite tv for pc imagery spanning 5 years, the scientists studied 7 glaciers in west Greenland terminating each on land and within the ocean, combining ice velocities obtained from GPS and the Sentinel-1 area satellite tv for pc with meteorological knowledge from climate stations.
In 2022, the west Greenland Ice Sheet skilled the biggest every day run-off within the late-melt season (late August onwards) since 1950. A succession of soften occasions occurred extending throughout ~37% of the ice sheet’s space because of an atmospheric river bringing heat air over the ice sheet that induced floor melting, peaking at 9.6 cm water equal per day.
Throughout these occasions, one of many climate stations at an elevation of 1823 m on the ice sheet recorded a speedy air temperature enhance from -17.7 °C to 2.7 °C in 24 hours.
Air temperature and floor power adjustments measured at Greenland Ice Sheet climate station KAN_L (a), modeled every day floor soften and precipitation (b) and every day soften extent (c). Credit score: Ing et al. 2024.
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Air temperature and floor power adjustments measured at Greenland Ice Sheet climate station KAN_L (a), modeled every day floor soften and precipitation (b) and every day soften extent (c). Credit score: Ing et al. 2024.
These soften occasions resulted within the subglacial drainage system turning into overwhelmed by floor meltwater, lubricating the bottom of the glacier by growing basal water strain. Consequently, a lower in basal friction led to a short lived enhance within the velocity of the ice sheet’s movement by as much as ~240% in comparison with pre-event velocities, reaching a most of 236 m y-1.
Nevertheless, as meltwater provide will increase by way of summer time, bigger subglacial channels develop, which will increase their carrying capability and reduces the lubrication impact on the bottom of the glacier, thus slowing its movement.
Additional explaining the differing impacts of seasonal melting on the Greenland Ice Sheet’s subglacial drainage system, Ing stated, “Through the late soften season, the channels beneath the ice, which transport meltwater, steadily contract as floor melting decreases. Subsequently, when a considerable surge in floor soften happens throughout this era, resembling from an atmospheric river occasion or cyclonic climate system, these channels turn out to be overwhelmed.”
“This results in a speedy enhance in basal water strain, inducing accelerations in ice circulation.”
“In distinction, throughout the peak of the soften season in summer time, there may be steady floor melting and water flowing by way of the channels, which enlarges them. Consequently, when there’s a soften occasion throughout this time of yr, the bigger channels can extra simply accommodate the additional meltwater, leading to much less pronounced will increase in basal water strain and ice movement.”
Attributable to this effectivity of the subglacial drainage system and the transient nature of the accelerations in ice movement, the examine discovered that the annual ice discharge of the ice sheet was not considerably impacted by adjustments in ice movement, with a rise (and due to this fact lack of ice mass) of ~4.5% mixed for land and marine-terminating glaciers (0.044 Gt ice, in comparison with imply annual ice discharge of 0.979 Gt y-1 for 2016-2022).
What was important, nonetheless, was the rise in complete annual runoff (the quantity of floor melting the ice sheet experiences in a yr), which elevated by ~24% due to these transient late-season soften occasions.
Whereas this examine means that the rise in annual ice discharge from these late-season soften occasions is not going to be a main think about ice sheet mass loss, the rise in meltwater runoff from such occasions is important and important. The transient late-season soften occasions of 2022 elevated the annual mass loss from soften by an order of magnitude greater than from the quite minimal ice acceleration.
That is particularly necessary given that fifty% of all the Greenland Ice Sheet’s annual mass loss is because of meltwater runoff. The results of enhanced late melt-season occasions might, due to this fact, turn out to be more and more necessary within the many years to come back as Earth’s local weather continues to heat.
Ing concluded that the outcomes of the examine is likely to be translated to different ice sheets and glaciers globally, highlighting the significance of additional analysis on this subject, “Whereas the particular findings of this examine pertain to the Greenland Ice Sheet, comparable conduct is prone to happen at different glaciers and ice sheets that additionally endure a seasonal cycle in ice movement linked to the seasonal cycle of floor soften.”
“This consists of alpine glaciers, excessive arctic ice caps, and the glaciers on the Antarctica peninsula, that are experiencing growing quantities of seasonal floor soften because of local weather change.”
Extra info:
Ryan N. Ing et al, Minimal Affect of Late‐Season Soften Occasions on Greenland Ice Sheet Annual Movement, Geophysical Analysis Letters (2024). DOI: 10.1029/2023GL106520
Journal info:
Geophysical Analysis Letters
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