Comment on ‘Mass gains of the Antarctic ice sheet exceed losses’ by H. J. Zwally and others
Comment on ‘Mass gains of the Antarctic ice sheet exceed losses’ by H. J. Zwally and others
复制标题
DOI：
10.1017/jog.2016.59
复制
发表时间：
2016-06
影响因子：
3.4
通讯作者：
T. Scambos;C. Shuman
中科院分区：
文献类型：
--
作者：
T. Scambos;C. Shuman
我们对Zwally等人最近在《冰川学杂志》（2015）上发表的一项研究（以下简称“Zwally 2015”）非常关注。这篇论文的结论是，南极冰盖的质量正在增加，这一结果与之前发表的大量研究结果不一致。在冰川学领域，目前最重要的问题莫过于增进我们对主要冰盖的冰质量平衡及其对海平面的影响的认识。这种增进了解的需要超出了冰川学界的范围，也包括决策者和普通公众。出于这个原因，我们认为有必要在这里指出用于得出2015年Zwally结果的方法存在问题的证据。在最近的南极物质平衡研究中，Zwally 2015的结论显然是一个异常值。结合1992-2001年的卫星雷达测高数据和2003 - 2008年的卫星激光测高数据，该报告声称，从2008年开始，在相当长的一段时间内，南极冰高度的净增长——以及由此产生的冰质量——已经超过了损失。我们对这篇论文的分析如下所示，揭示了导致正质量平衡的信号的最大组成部分是南极东部冰盖（EAIS）内部的地表高度增加，特别是在冰、云和陆地高程卫星（ICESat）激光测高期间。这取决于利用这些卫星数据确定的厘米a−1高程变化。Zwally 2015年基于ICESat数据（2003-08）对整个冰盖的预测结果为+ 82±25 Gt a−1，而自2012年以来发表的其他11项研究在类似时期的平均值约为- 80+ 60/ - 100 Gt a−1（图1）。最近没有其他评估报告明确指出整个大陆的冰量增加。冰质量平衡相互比较练习（IMBIE）（Shepherd等人，2012年）是对当时几乎所有高质量质量平衡估计的调和，包括Zwally 2015作者的早期结果。该研究报告称，在ICESat期间，整个南极洲的总体冰量平衡为- 72±43 Gt a - 1，仅EAIS地区的冰量平衡为+ 58±31 Gt a - 1。相比之下，在Zwally 2015中，EAIS的质量平衡为+ 136±28 Gt a−1，是调和后的IMBIE值的2.3倍。
We have significant concerns with a study recently published in the Journal of Glaciology by Zwally and others (2015), hereafter ‘Zwally 2015’. The paper concludes that the Antarctic ice-sheet mass is increasing, a result that is inconsistent with a large body of previously published work. No issue in the field of glaciology is currently more critical than the improvement of our understanding of ice mass balance for the major ice sheets and its consequent impact on sea level. This need for an improved understanding extends beyond the glaciological community and includes policy makers and the general public. For this reason, we feel that it is important to note here the evidence for problems with the methodologies used to arrive at the Zwally 2015 result. The Zwally 2015 conclusion is clearly an outlier among recent studies of Antarctic mass balance. Combining satellite radar altimetry spanning 1992–2001 and satellite laser altimetry from 2003 to 2008, it purports to show that as of 2008, and for an extended period, net gains in Antarctic ice elevation–and therefore ice mass–have exceeded losses. Our analysis of the paper, presented below, reveals that the largest component of the signal leading to the positive mass balance is a surface elevation increase in the East Antarctic ice sheet (EAIS) interior, particularly for the Ice, Cloud, and land Elevation Satellite (ICESat) laser altimetry period. This is dependent upon cm a− 1 elevation change determinations using those satellite data.Zwally 2015 report+ 82±25 Gt a− 1 for the ice sheet as a whole based on their ICESat data (2003–08), whereas the mean of eleven other studies published since 2012 for a similar period is approximately− 80+ 60/− 100 Gt a− 1 (Fig. 1). No other recent assessment reports an unambiguous ice mass gain for the whole continent. The Ice Mass Balance Intercomparison Exercise (IMBIE)(Shepherd and others, 2012) was a reconciliation of nearly all highquality mass-balance estimates at that time, and included earlier results from the Zwally 2015 authors. That study reported an overall ice mass balance for the ICESat period of− 72±43 Gt a− 1 for all of Antarctica, and+ 58±31 Gt a− 1 for the EAIS alone. For comparison, in Zwally 2015 the mass balance for the EAIS is+ 136±28 Gt a− 1, 2.3 times the reconciled IMBIE value.