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Statistical Modeling for Glacier Loss: Is It Correct?
Glacier loss is a urgent concern worldwide, with ice soften impacting freshwater provides, sea-level rise and ocean circulation. Typically, international glacier fashions are employed to raised perceive the extent of this menace, resembling a current mannequin that reveals widespread deglaciation in mid-latitudes by 2100. Nonetheless, with this mannequin and others, there are uncertainties concerning any linear relationship between temperature and glacier loss, notably in areas like Iceland that have temperature extremes deviating from the worldwide common.
A examine performed on Bruarjokull, a glacier in Iceland, evaluated this uncertainty additional, and located that the linear relationship can’t be readily defined by native observations alone. This implies the necessity to examine Icelandic glaciers as a community. The examine, based mostly on this writer’s thesis challenge at Leiden College Faculty within the Netherlands, used satellite tv for pc imagery and information from the closest climate station to make a mannequin of the realm lack of the glacier from 1984 to 2020. Such retrospective fashions, known as hindcasts, can be utilized to validate fashions for projections of future adjustments.
Conventional strategies of learning glaciers contain time-consuming and resource-intensive bodily measurements, so researchers generally use mathematical fashions to conduct their work as a substitute. Two sorts of mathematical fashions are related on this context: deterministic and statistical fashions. Deterministic fashions are a sort of mathematical mannequin that use bodily legal guidelines to simulate the conduct of a system. Statistical fashions, alternatively, are based mostly on correlations between noticed information, and are carried out to make predictions or estimates.
Complicated deterministic fashions on a worldwide scale aren’t conscious of native climate situations, so statistical fashions have emerged as a possible various to learning glacier soften. One instance of such a statistical mannequin is within the 2001 guide Glaciers and Local weather Change, by climatologist Hans Oerlemans. He discovered that steady local weather situations nonetheless led to glacier soften within the European Alps. One other instance comes from a current examine revealed within the journal Nature that evaluated glacier retreat of the Naradu Glacier within the Western Himalaya. This examine, led by Central College of Rajasthan Professor Rajesh Kumar, got here to the conclusion that lowering precipitation is a extra necessary driver of glacier soften there than rising temperature.
Previous to the newest examine from Iceland, members of our analysis staff tried to copy the outcomes of Kumar and his colleagues, utilizing their information and methodology. After months of information manipulation and trying to contact the authors to achieve extra info, we had been unable to acquire any of the outcomes revealed of their paper. This problem led us to grow to be curious concerning the methodology itself, and we selected to copy it with new information for Bruarjokull glacier in Iceland.
Iceland is dwelling to a few of the world’s largest ice caps, together with Langjokull and Vatnajokull. These ice caps and their outlet glaciers are vital elements of the nation’s freshwater provide, tourism trade and ecosystem. Nonetheless, local weather change is inflicting them to soften at a fast price, main some to say that Iceland’s glaciers will disappear within the subsequent 150 years.
The examine based mostly on Bruarjokull discovered precipitation fairly than temperature to be the important thing local weather driver of glacier space. This discovering contrasts with stories that point out temperature is the important thing local weather driver of Icelandic glaciers. However the examine additional finds that linear modeling of Bruarjokull space as a operate of precipitation can’t be reliably used for short-term or long-term forecasting of glacier extent.
The nuance lies the place one seems to be on the mannequin residuals—the variations between noticed and predicted values of information. The residuals are used when assessing the standard of a mannequin as a diagnostic measure. On this case, the examine signifies that glacier-meteorological dynamics could also be solely partially modeled linearly, however that the mannequin efficiently explains underlying developments within the area-precipitation relationship.
Whereas this may sound like a contradiction, it highlights one thing greater. A examine in Greenland equally discovered that particular person glacier dynamics are defined non-linearly. Nonetheless, they present that normalized glacier change is homogeneous over higher areas. In different phrases, glaciers don’t must be modeled individually to mannequin ice loss as a operate of local weather in that area. This brings us again to the worldwide glacier fashions, which might run with decreased computational prices, and mannequin complexity for areas with local weather anomalies exterior the worldwide common. Whether or not or not regional modeling applies to Icelandic glaciers can’t be strictly decided from the current findings, however this does spotlight an thrilling new alternative.
Different strategies, particularly non-linear statistical fashions or synthetic neural networks, can be utilized for native glacier research. This highlights the necessity for extra refined, complete and costly information higher fitted to learning glaciers (versus normal climate station information that was used within the examine). Obstacles together with glaciers’ typically distant and treacherous environments counsel that it might not be doable to amass the info mandatory for statistical fashions to precisely predict glacier soften. On this case, we could must rethink the strategies used for learning Icelandic glaciers, given the boundaries of the info. By doing so, we are able to discover connections amongst regional glacier networks and higher inform international fashions.
Domino Jones is an undergraduate pupil at Leiden College Faculty within the Netherlands, majoring in Earth, Power and Sustainability.
GlacierHub is a local weather communication initiative led by Ben Orlove, an anthropologist on the Columbia Local weather College. A lot of GlacierHub’s writers are Local weather College college students or alumni.
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