Holocene climatic change in the Alaskan Arctic as inferred from oxygen-isotope and lake-sediment analyses at Wahoo Lake
Holocene climatic change in the Alaskan Arctic as inferred from oxygen-isotope and lake-sediment analyses at Wahoo Lake
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DOI：
10.1177/0959683617702230
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发表时间：
2017-04
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影响因子：
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通讯作者：
R. Vachula;M. Chipman;F. Hu
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作者：
R. Vachula;M. Chipman;F. Hu
尽管最近在理解高纬度气候变异性方面取得了进展，但阿拉斯加北极地区的古气候记录很少。我们在瓦虎湖进行了同位素和沉积物分析，以推断阿拉斯加东北部全新世的气候变异性。来自该湖及其进出口溪流的水δ18O和δD值表明，冬季降水在现代水输入中占主导地位，蒸发对湖泊水文收支的影响有限。Pisidium的同位素组成在过去的11500年中表现出显著的变化，δ18O在−18.7‰到−16.2‰之间，δ13C在−7.1‰到−2.3‰(维也纳Pee Dee Belemnite(VPDB))之间。δ18O升高，沉积物组成从11.5千卡增加到8.9千卡。BP反映了蒸发~(18)O的富集度和干旱条件。湖泊水位上升的证据是Pisidium的消失和约6.3千卡的低碳酸盐Gyttja的过渡。BP和邻近陆架的沉积物沉积开始增加5.3千卡。BP。从湖面记录推断，这些变化与阿拉斯加内陆和南部的有效湿度增加相吻合，可能与大范围的大气环流变化有关。在陆架沉积物中，碳酸盐丰度在3.5kcal时显著增加。BP，δ18O在2.1kcal时从−18.0‰增加到−16.5‰。BP，可能是由于气温和/或夏季降水增加所致。在2.1千卡之后。BP，δ18O波动，总体趋势是下降至0.9千卡的−17.2‰。BP。我们的δ18O记录中的晚全新世变化与百年至千年尺度的区域冰川波动显示出一致的模式，表明δ18O极小值与低温和冬季降雪增加的组合有关。瓦虎湖全新世有机质丰度的变化也显示出与太阳总辐射的广泛相似之处，这意味着亚轨道太阳变化在调节区域气候和水生生产力方面发挥了作用。
Despite recent progress in understanding high-latitude climate variability, paleoclimate records are scarce from the Alaskan Arctic. We conducted isotopic and sediment analyses at Wahoo Lake to infer Holocene climate variability in northeastern Alaska. Water δ18O and δD values from the lake and its inlet/outlet streams suggest that winter precipitation dominates modern water inputs and that evaporation has limited influence on the lake’s hydrological budget. The isotopic composition of Pisidium exhibits marked variations during the past 11,500 years, with δ18O ranging between −18.7‰ and −16.2‰ and δ13C between −7.1‰ and −2.3‰ (Vienna Pee Dee Belemnite (VPDB)). Elevated δ18O and sediment composition from 11.5 to 8.9 kcal. BP suggest evaporative 18O enrichment and arid conditions. Rising lake levels are evidenced by the disappearance of Pisidium and a transition to low-carbonate gyttja ca. 6.3 kcal. BP and by the onset of sediment deposition on an adjacent shelf by 5.3 kcal. BP. These changes coincided with enhanced effective moisture in interior and southern Alaska as inferred from lake-level records and may be related to broad-scale atmospheric circulation changes. In the shelf sediments, carbonate abundance increases markedly at 3.5 kcal. BP, and δ18O increases from −18.0‰ to −16.5‰ at 2.1 kcal. BP, possibly resulting from increased temperature and/or summer precipitation. After 2.1 kcal. BP, δ18O fluctuates with an overall decreasing trend to −17.2‰ at 0.9 kcal. BP. Late-Holocene variations in our δ18O record display coherent patterns with regional glacier fluctuations at centennial to millennial scales, suggesting that δ18O minima were related to a combination of low temperatures and enhanced winter snowfall. Holocene variations in organic matter abundance at Wahoo Lake also show broad similarities to total solar irradiance, implying that suborbital solar variability played a role in modulating regional climate and aquatic productivity.