Resolving combined influences of inflow and evaporation on western Greenland lake water isotopes to inform paleoclimate inferences
Resolving combined influences of inflow and evaporation on western Greenland lake water isotopes to inform paleoclimate inferences
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DOI：
10.1007/s10933-020-00114-4
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发表时间：
2020-02-05
影响因子：
2.1
通讯作者：
Thomas, E. K.
中科院分区：
文献类型：
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作者：
Cluett, A. A.;Thomas, E. K.
降水中氧（δ O-18）和氢（δ H-2）的稳定同位素被广泛用于全球水文循环的示踪，并经常从高纬度湖泊沉积物中的湖水来源代用品中推断。湖水同位素代理存档降水三角洲O-18和三角洲H-2值，调制湖泊水文过程，这可能会在功能上分为影响源水同位素值（即流入三角洲O-18和三角洲H-2）和集水区综合蒸发的过程。这些控制分别形成降水同位素和有效降水信号从湖水同位素代用记录的解释的基础。传统上，一个单一的控制湖水同位素变化是假定为一个给定的记录。然而，这些控制的敏感性取决于区域水文气候和当地水文，这可能会随着时间的推移而变化。我们量化的相对影响流入三角洲O-18和蒸发O-18富集湖水三角洲O-18响应空间变化的干旱，使用测量的湖水三角洲H-2和三角洲O-18从140个格陵兰西部湖泊位于拉布拉多海和格陵兰西部冰盖边缘之间。我们计算了源水三角洲O-18湖沃茨（三角洲I）使用最近开发的贝叶斯方法和量化的蒸发流入比（E/I）使用修改后的Craig-Gordon模型。在整个研究区域内，δ I的变化为11.1ppm，加上蒸发O-18富集高达20 ppm，E/I范围从几乎没有蒸发损失（E/I < 0.10）到干燥（E/I > 1）。湖泊可以大致归类为主要敏感流入或蒸发，对应于他们的位置沿着干旱梯度，并有显着的趋势，在三角洲I和E/I整个研究区。三角洲I和E/I的大量本地变化表明，流域水文决定了三角洲I和E/I的敏感性，干旱的变化，并意味着在一个小区域内的水文端员湖泊可以提供季节性降水同位素值和无冰季节蒸发的补充记录。对湖水同位素值进行现代控制的去卷积为根据古湖泊同位素数据进行定量和季节性古气候推断提供了必要的支持，这将改善对北极水文循环长期变化的限制。
Stable isotopes of oxygen (delta O-18) and hydrogen (delta H-2) in precipitation are widely employed tracers of the global hydrologic cycle, and are frequently inferred from lake-water-derived proxies in sediments of high-latitude lakes. Lake-water isotope proxies archive precipitation delta O-18 and delta H-2 values, modulated by lake hydrological processes, which may be functionally classified into processes that affect source water isotope values (i.e. inflow delta O-18 and delta H-2) and catchment-integrated evaporation. Respectively, these controls form the basis of interpretations of precipitation isotope and effective precipitation signals from lake-water isotope proxy records. Conventionally, a single control on lake water isotope variability is assumed for a given record. Yet sensitivity to these controls depends on regional hydroclimate and local hydrology, which may change through time. We quantified the relative impacts of variations in inflow delta O-18 and evaporative O-18 enrichment on lake water delta O-18 in response to spatially variable aridity, using measurements of lake water delta H-2 and delta O-18 from 140 western Greenland lakes located between the Labrador Sea and western Greenland Ice Sheet margin. We calculated source water delta O-18 of lake waters (delta I) using a recently developed Bayesian method and quantified evaporation-to-inflow ratios (E/I) using a modified Craig-Gordon model. delta I varied by 11.1 parts per thousand across the study region, superimposed by evaporative O-18 enrichment of up to 20.0 parts per thousand and E/I ranging from nearly no evaporative loss (E/I < 0.10) to desiccation (E/I > 1). Lakes can be broadly classified as predominantly sensitive to inflow or evaporation, corresponding to their location along the aridity gradient, and there are significant trends in both delta I and E/I across the study area. Substantial local variability in delta I and E/I suggests catchment hydrology determines the sensitivity of delta I and E/I to changes in aridity, and implies that hydrological end-member lakes within a small region may provide complementary records of seasonal precipitation isotope values and ice-free-season evaporation. Deconvolving modern controls on lake water isotope values provides essential support for quantitative and seasonal paleoclimate inferences from paleolimnological isotope data, which will improve constraints on the long-term variability of the Arctic hydrologic cycle.