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Abstract. Given the short span of instrumental precipitationrecords in the South American Altiplano, longer-term hydroclimatic recordsare needed to understand the nature of climate variability and to improvethe predictability of precipitation, a key natural resource for thesocioeconomic development in the Altiplano and adjacent arid lowlands. Inthis region grows Polylepis tarapacana, a long-lived tree species that is very sensitive tohydroclimatic changes and has been widely used for tree-ring studies in thecentral and southern Altiplano. However, in the northern sector of thePeruvian and Chilean Altiplano (16–19∘ S)still exists a gap of high-resolution hydroclimatic data based on tree-ringrecords. Our study provides an overview of the temporal evolution of thelate-spring–mid-summer precipitation for the period 1625–2013 CE at thenorthern South American Altiplano, allowing for the identification of wet ordry periods based on a regional reconstruction from three P. tarapacana chronologies. Anincrease in the occurrence of extreme dry events, together with a decreasingtrend in the reconstructed precipitation, has been recorded since the 1970sin the northern Altiplano within the context of the last ∼4 centuries. The average precipitation over the last 17 years stands outas the driest in our 389-year reconstruction. We reveal a temporal andspatial synchrony across the Altiplano region of dry conditions since themid-1970s. Independent tree-ring-based hydroclimate reconstructions andseveral paleoclimatic records based on other proxies available for thetropical Andes record this synchrony. The influence of El Niño–SouthernOscillation (ENSO) on the northern Altiplano precipitation was detected byour rainfall reconstruction that showed past drier conditions in our studyregion associated with ENSO warm events. The spectral properties of therainfall reconstruction showed strong imprints of ENSO variability atdecadal, sub-decadal, and inter-annual timescales, in particular from thePacific NIÑO 3 sector. Overall, the recent reduction in precipitation incomparison with previous centuries, the increase in extreme dry events andthe coupling between precipitation and ENSO variability reported by thiswork is essential information in the context of the growing demand for waterresources in the Altiplano. This study will contribute to a betterunderstanding of the vulnerability and resilience of the region to theprojected evapotranspiration increase for the 21st century associated withglobal warming.
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Reconstructing extreme precipitation in the Sacramento River Watershed using tree-ring based proxies of cold-season precipitation
Extreme precipitation and consequent floods are some of California's most damaging natural disasters, but they are also critical to the state's water supply. This motivates the need to better understand the long-term variability of these events across the region. This study examines the possibility of reconstructing extreme precipitation occurrences in the Sacramento River Watershed (SRW) of Northern California using a network of tree-ring based moisture proxies across the Western US. We first develop a gridded reconstruction of the cold-season standardized precipitation index (SPI) west of 100°W. We then develop an annual index of regional extreme precipitation occurrences in the SRW and use elastic net regression to relate that index to the gridded, tree-ring based SPI. These regressions, built using SPI data across the SRW only and again across a broader region of the Western US, are used to develop reconstructions of interannual variability in extreme precipitation frequency back to 1400 CE. The SPI reconstruction is skillful across much of the West, including the Sacramento Valley and Central Oregon. The reconstructed SPI also captures historical interannual variations in extreme SRW precipitation, although individual events may be under- or over-estimated. The reconstructions show more SRW extremes from 1580 to 1700 and 1850 to 1915, a dearth of extremes prior to 1550, and a 2–8 year oscillation after 1550. Using tree-ring proxies beyond the SRW often dampens the reconstructed extremes, but these data occasionally help to identify known extreme events. Overall, reconstructions of SRW extreme precipitation can help to understand better the historic variability of these events.
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- Award ID(s):
- 1702273
- PAR ID:
- 10296568
- Date Published:
- Journal Name:
- Water resources research
- Volume:
- 57
- Issue:
- 4
- ISSN:
- 1944-7973
- Page Range / eLocation ID:
- e2020WR028824
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/https://doi.org/10.1029/2020WR028824
