NOAA/WDS Paleoclimatology - Pederson - Prospect Mountain - CYOV - ITRDB NY034

Six water emergencies have occurred since 1981 for the New York City region (NYC) despite: 1) its perhumid climate, 2) substantial conservation of water since 1979 and 3) meteorological data showing little severe or extreme drought since 1970. We reconstruct 472 years of moisture availability for the NYC watershed to place these emergencies in long-term hydroclimatic context. Using nested reconstruction techniques, 32 tree-ring chronologies comprised of 12 species account for up to 66.2% of the average May-August Palmer Drought Severity Index. Verification statistics indicate good statistical skill from 1531-2003. The use of multiple tree species, including rarely-used species that can sometimes occur on mesic sites like Liriodendron tulipifera, Betula lenta and Carya spp., seems to aid reconstruction skill. Importantly, the reconstruction captures pluvial events in the instrumental record nearly as well as drought events and is significantly correlated to precipitation over much of the northeastern US. While the mid-1960s drought is a severe drought in the context of the new reconstruction, the region experienced repeated droughts of similar intensity, but greater duration during the 16th and 17th centuries. The full record reveals a trend towards more pluvial conditions since ca 1800 that is accentuated by an unprecedented, 43-year pluvial event that continues through 2011. In the context of the current pluvial, decreasing water usage, but increasing extra-urban pressures, it appears that the water supply system for the greater NYC region could be severely stressed if the current water boom shifts towards hydroclimatic regimes like the 16th and 17th centuries.

自1981年以来，纽约都会区（New York City region, 简称NYC）已发生6起供水紧急事件，尽管该区域具备以下特征：1）超湿润的气候环境；2）自1979年起持续开展大规模水资源保护工作；3）气象观测数据显示1970年以来极少出现严重或极端干旱事件。本研究重建了纽约都会区流域472年的水分可利用性序列，以将上述供水紧急事件置于长期水文气候背景下开展分析。研究采用嵌套重建技术，基于涵盖12个树种的32组树木年轮年表，可解释5月至8月平均帕尔默干旱严重指数（Palmer Drought Severity Index）中最高达66.2%的变异。验证统计结果表明，该重建序列在1531年至2003年间具备良好的统计效能。研究选用了包括鹅掌楸（Liriodendron tulipifera）、黑桦（Betula lenta）以及山核桃属（Carya spp.）在内的多种树种，其中部分为较少用于重建分析的物种，且这些物种有时可生长于中生境中，这一选材策略似乎有助于提升重建的统计效能。值得注意的是，本重建序列对器测记录中洪涝事件的还原效果几乎与干旱事件相当，且与美国东北部大部分区域的降水序列显著相关。尽管在本次重建的背景下，1960年代中期的干旱属于严重干旱事件，但该区域在16世纪和17世纪曾经历过强度相当、但持续时间更长的多次干旱事件。完整的重建序列显示，约自1800年以来，区域气候呈现向更湿润条件转变的趋势，而这一趋势因一场持续至2011年、长达43年的前所未有的湿润事件而被进一步强化。在当前湿润气候背景下，尽管区域用水需求有所下降，但城市外围的供水压力持续增加，若当前的湿润气候格局转向16至17世纪的水文气候模态，大纽约都会区的供水系统或将面临严重的运行压力。