Interrogating glacier mass balance response to climatic change since the Little Ice Age: reconstructions for the Jotunheimen region, southern Norway

IF 2.4 3区 地球科学 Q2 GEOGRAPHY, PHYSICAL
Boreas Pub Date : 2021-10-15 DOI:10.1111/bor.12562
John F. Hiemstra, Giles H. F. Young, Neil J. Loader, Penny R. Gordon
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引用次数: 1

Abstract

Developing a long-term understanding of the cryosphere is important in the study of past climatic change. Here we used a nested approach combining diverse instrumental (monthly meteorological data from four weather stations, as well as gridded data) and proxy data (based on blue intensity measurements from local tree ring records) to create a reconstruction of past summer temperature for the central Jotunheimen area in southern Norway. This record was then used to reconstruct annual glacier mass balance from 1962, the start of the yearly measurements, back to 1722, immediately prior to the regional Little Ice Age maximum. Our reconstruction of the ‘average’ Jotunheimen cumulative glacier mass balance is based on three representative glaciers (Storbreen, Hellstugubreen and Gråsubreen) that were synthesized into one composite record which we term ‘Gjennomsnittsbreen’ (‘mean glacier’ in Norwegian) to filter out localized controls on the behaviour of individual glaciers. While not ignoring the role of precipitation on glacier mass balance, our reconstruction demonstrates that glaciers in this region exhibit a strong summer temperature control and appear to have been declining more or less continuously since the mid-18th century. However, it also shows that this long-term trend of overall retreat in Jotunheimen is punctuated by relatively short-lived periods of neutral or occasionally positive glacier mass balance, signifying periods of stillstand or small-scale glacier advance. These periods or ‘events’ in our reconstruction were compared with an independent record of 12 moraine-building events developed using lichenometry. A minimum of 10 of the moraine-building events identifiable in our reconstruction were also identifiable in the lichenometric data which affords confidence in the performance of our interrogative model. A critical implication of this successful glacier mass balance reconstruction based on just summer temperature is that for Jotunheimen – in contrast to Norwegian maritime glaciers further to the west – there is no need (as was proposed in some previous studies) to invoke large, prolonged increases in winter snowfall to explain glacier advances, not even for events such as the Little Ice Age.

Abstract Image

小冰期以来冰川质量平衡对气候变化的响应:挪威南部Jotunheimen地区的重建
发展对冰冻圈的长期认识对于研究过去的气候变化是重要的。在这里,我们使用了一种巢式方法,结合了各种仪器(来自四个气象站的月度气象数据,以及网格数据)和代理数据(基于当地树木年轮记录的蓝色强度测量),来重建挪威南部Jotunheimen中部地区过去的夏季温度。这一记录随后被用来重建从1962年开始的年度测量的年度冰川质量平衡,一直追溯到1722年,就在区域小冰期高峰之前。我们对Jotunheimen累积冰川物质平衡的“平均”重建是基于三个代表性冰川(Storbreen, Hellstugubreen和gr subreen),这些冰川被合成为一个综合记录,我们称之为“Gjennomsnittsbreen”(挪威语中的“平均冰川”),以过滤掉对单个冰川行为的局部控制。虽然没有忽略降水对冰川物质平衡的作用,但我们的重建表明,该地区的冰川表现出强烈的夏季温度控制,并且自18世纪中期以来似乎一直在或多或少地持续下降。然而,这也表明,Jotunheimen整体退缩的长期趋势被相对较短的冰川质量平衡中性或偶尔为正的时期所打断,这意味着静止或小尺度冰川前进的时期。我们重建的这些时期或“事件”与使用地衣测量法记录的12个冰碛形成事件的独立记录进行了比较。在我们的重建中可识别的冰碛形成事件中,至少有10个在地衣测量数据中也可识别,这为我们的疑问模型的性能提供了信心。这一成功的基于夏季温度的冰川质量平衡重建的一个关键含义是,对于Jotunheimen来说——与更西面的挪威海洋冰川相反——没有必要(正如之前的一些研究中提出的那样)援引冬季降雪的大规模、长期增加来解释冰川的进展,甚至连小冰河期这样的事件也没有必要。
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来源期刊
Boreas
Boreas 地学-地球科学综合
CiteScore
5.90
自引率
4.50%
发文量
36
审稿时长
>12 weeks
期刊介绍: Boreas has been published since 1972. Articles of wide international interest from all branches of Quaternary research are published. Biological as well as non-biological aspects of the Quaternary environment, in both glaciated and non-glaciated areas, are dealt with: Climate, shore displacement, glacial features, landforms, sediments, organisms and their habitat, and stratigraphical and chronological relationships. Anticipated international interest, at least within a continent or a considerable part of it, is a main criterion for the acceptance of papers. Besides articles, short items like discussion contributions and book reviews are published.
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