调查最后一次冰期劳伦泰德冰原的地表质量平衡

IF 3.8 2区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY
Kirstin Koepnick, Minmin Fu, Eli Tziperman
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引用次数: 0

摘要

摘要尽管经过数十年的研究,气候反馈在更新世冰川周期中的作用仍未被完全理解。在此,我们利用同位素瞬态气候模式实验(iTraCE)计算了劳伦泰德冰原(LIS)在上一次冰川期的地表质量平衡(SMB)。利用地表能量平衡框架计算年融化量,并将融雪和液态降水的再冻结参数化纳入其中。与 ICE-6G 重建结果相比,iTraCE 计算出的 SMB 高估了从末次冰川极盛时期(LGM;21 ka)到大约 15-14 ka 期间的总冰量损失率;随后,完全强迫气候模式实验更符合 ICE-6G 冰量损失率。我们发现,LIS 的融化率主要是由大量净短波和长波辐射通量的微小残差决定的。融化率以及 SMB 对反照率和下沉长波辐射的微小变化非常敏感。只需将反照率提高 1.9% 或将下沉长波辐射降低 1.45%(完全在这些变量的不确定性范围内),就可以消除从 SMB 推断出的质量损失率与重建的 19-15 ka 年质量损失率相比被大幅高估的现象。气候模式离线计算出的 SMB 与冰质量重建结果不一致,与冰流造成的消融作用无关,因为冰流无法通过这种分析计算出来。融化率的极端敏感性表明,大气环流模式(GCMs)仍然难以可靠地计算 SMB,这对我们试图了解更新世冰期是一个重大障碍。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Investigating the surface mass balance of the Laurentide Ice Sheet during the last deglaciation
Abstract. In spite of decades of research, the role of climate feedbacks in the Pleistocene glacial cycles is still not fully understood. Here, we calculate the surface mass balance (SMB) of the Laurentide Ice Sheet (LIS) throughout the last deglaciation using the isotope-enabled transient climate model experiment (iTraCE). A surface energy balance framework is used to calculate yearly melt, and a parameterization of the refreezing of snow melt and liquid precipitation is incorporated. The SMB calculated from iTraCE overestimates the total ice mass loss rate in comparison to the ICE-6G reconstruction from the Last Glacial Maximum (LGM; 21 ka) until about 15–14 ka; subsequently, the fully forced climate model experiment better fits the ICE-6G ice volume loss rate. We find the melt rate for the LIS to be primarily set by the small residual of large net shortwave and longwave radiative fluxes. The melt, and hence the SMB, are very sensitive to small changes in the albedo and downwelling longwave radiation. By increasing albedo by a mere 1.9 % or by decreasing downwelling longwave radiation by only 1.45 % (well within the uncertainty range of these variables), the large overestimation of the rate of mass loss deduced from the SMB compared to reconstructed rates of mass loss from 19–15 ka can be eliminated. The inconsistency of the climate model-derived, offline SMB calculation and the ice mass reconstructions exists irrespective of the role of ablation caused by ice flow, which cannot be calculated using this analysis. The extreme sensitivity of the melt rate suggests that General Circulation Models (GCMs) still struggle to reliably calculate the SMB, presenting a significant roadblock in our attempt to understand the Pleistocene ice ages.
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来源期刊
Climate of The Past
Climate of The Past 地学-气象与大气科学
CiteScore
7.40
自引率
14.00%
发文量
120
审稿时长
4-8 weeks
期刊介绍: Climate of the Past (CP) is a not-for-profit international scientific journal dedicated to the publication and discussion of research articles, short communications, and review papers on the climate history of the Earth. CP covers all temporal scales of climate change and variability, from geological time through to multidecadal studies of the last century. Studies focusing mainly on present and future climate are not within scope. The main subject areas are the following: reconstructions of past climate based on instrumental and historical data as well as proxy data from marine and terrestrial (including ice) archives; development and validation of new proxies, improvements of the precision and accuracy of proxy data; theoretical and empirical studies of processes in and feedback mechanisms between all climate system components in relation to past climate change on all space scales and timescales; simulation of past climate and model-based interpretation of palaeoclimate data for a better understanding of present and future climate variability and climate change.
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