60-year trends of δ18O in global precipitation reveal large scale hydroclimatic variations

https://doi.org/10.1016/j.gloplacha.2020.103335Get rights and content

Highlights

  • Break points in long-term GNIP δ18O time series affirm alterations in atmospheric oscillations

  • Atlantic and Pacific Oscillation influences were reflected in the δ18O precipitation time series

  • Sinusoidal δ18O trends in oceanic island stations reveal multidecadal hydroclimatic patterns

Abstract

Sixty years of monthly data series of δ18O in precipitation revealed distinctive decadal long-term patterns and break points for the isotope composition of global precipitation. Our results showed that at the multi-decadal scale, δ18O in precipitation displayed changes due to large-scale hydroclimate processes, and particularly, from atmospheric oscillations. Break point and segmented regression trend analyses for δ18O and air temperature revealed influences of the North Atlantic Oscillation (NAO) on the long-term isotope variability for most continental stations in Northern Hemisphere. Long-term trends of δ18O and precipitation amount for Southern Hemisphere stations were mostly indicative of changes in regional hydroclimate processes driven by the larger scale Atlantic and Pacific atmospheric oscillations. For oceanic island stations, the δ18O variations could be described by sinusoidal trends with a ~ 20–40 years-time cycle and δ18O amplitude of ~1–2‰, suggesting these stations have a higher sensitivity to multi-decadal atmospheric circulation. Our findings reveal that coordinated long-term monitoring of stable isotopes in precipitation, coupled with basic meteorological parameters such as air temperature and precipitation amount, are essential to better understand the impact of larger scale hydroclimate variation on regional and local climate variability, and to help interpret long-term hydroclimatic changes of the past, present and future.

Introduction

Atmospheric oscillations across the planet have a strong impact on hydroclimate processes at different spatial scales (Baldini et al., 2008; Kurtz, 2015). These global oscillations have frequencies ranging from weeks to multidecadal periods; some of them can be predicted whereas others cannot (Mantua and Hare, 2002; Baldini et al., 2008; Kurtz, 2015; Comas-Bru et al., 2016). The North Atlantic Oscillation (NAO), the Pacific Decadal (PDO), and Atlantic Multi-decadal (AMO) are the most important decadal and multi-decadal oscillations that control inter-annual climate variability at global scales (Sutton and Hodson, 2005; Kurzt 2015; Wang et al., 2017).

The NAO is known to modulate inter-annual atmospheric variability in the Northern Hemisphere and is a key driver of climate and weather in mid- to high- latitudinal North Atlantic regions, but at unpredictable periodicities from multi-daily to decadal (Baldini et al., 2008). The NAO “index” is determined from normalized pressure anomalies at the Azores and Iceland and is often interlinked to East Atlantic influence. Weak NAO activities (NAO-) deviate air masses towards the Mediterranean and eventually back to Central Europe, as observed in the decades before the late 1980's. Strong NAO activities (NAO+) diminished the influence of Atlantic moisture over the past few decades (Comas-Bru et al., 2016; Deininger et al., 2016). These variations in NAO activities are related to changes in air temperature and precipitation in a site and time-specific way (Comas-Bru et al., 2016; Deininger et al., 2016). NAO has also been linked to cyclonic activities (Vb-cyclones) in the Northern Hemisphere (Hofstätter and Blöschl, 2019).

In the Southern Hemisphere, Pacific atmospheric air mass circulation is largely associated with the El Niño-Southern Oscillation (ENSO), which brings hotter and drier weather during El Niño phase whereas cooler and wetter conditions prevail during La Niña phase (Mantua and Hare, 2002). Some scientists relate ENSO to PDO and consider PDO to be a long-lived El Niño-like pattern of Pacific climate variability, but others consider both as time independent modes with distinctive spatial and temporal characteristics of North Pacific temperature variability (Mantua and Hare, 2002). In any case, both oscillations are important determinants of climate in the mid-latitudes and may be responsible for air and sea water temperature rise since the early 1980's (Mantua and Hare, 2002). The AMO has a strong impact on global air mass circulation and particularly on rainfall patterns, acting with various frequencies and different regional patterns (Sutton and Hodson, 2005; Wang et al., 2017).

Stable isotope ratios (18O/16O, 2H/H) of precipitation collected from stations worldwide are well-known sensitive indicators of hydroclimatic variations, and depending on the precipitation collection frequency (e.g. events, monthly composites) and timeframe (years, decades) can be used as proxies to study large scale atmospheric circulations (Baldini et al., 2008; Liu et al., 2010; Kurtz, 2015; Comas-Bru et al., 2016). Stable isotopes in precipitation may also reflect decadal and lower frequency atmospheric oscillations (e.g. El Nino, El Nina, NAO, Pacific North American) (Liu et al., 2011; Brown et al., 2006), however, long isotope time series are generally needed to detect multi-decadal climatic oscillations (Kurtz, 2015; Gao et al., 2016). Additionally, the isotope composition of precipitation driven by global air mass circulation may be further modified by local and regional hydroclimatic processes, such as sub-cloud evaporation, convective and moisture recycling processes (Dansgaard, 1964; Rozanski et al., 1982, Rozanski et al., 1992; Araguás-Araguás et al., 2000; Brown et al., 2006; Aggarwal et al., 2012, Aggarwal et al., 2016; Wang et al., 2017). Accordingly, stable isotopes (δ18O and δ2H) have been used as long-term (hundreds to thousands of years) proxies of hydroclimate variation in ice cores, tree rings, speleothems, etc. (Raymo et al., 2006; Azzoug et al., 2012; Finkenbinder et al., 2016). Paleoclimate proxies integrate past precipitation events over various time frames; however, many proxies cannot be used for detecting distinctive changes in hydroclimate variations over monthly or annual decadal scales.

To gain a better understanding of hydroclimate variations over the past decades, we focused on long-term (60-year) records and trends of δ18O in precipitation as well as air temperature and precipitation for 21 meteorological stations worldwide located in diverse climate and geographical zones. The isotope and climatic data were used to detect hydroclimate variations that influence the isotope composition of global precipitation. Our findings contribute to reducing uncertainties in our understanding of global long-term temporal variations of stable isotopes in precipitation and offer some directions for hydrological predictions and climatic modelling. Based on our results we were able to identify gaps in the organization of future global observation strategies and proposed helpful directions for the long-term monitoring of stable isotopes in precipitation.

Section snippets

Study area and data collection

Long-term world-wide records of stable isotopes in monthly composites of precipitation and associated meteorological data were obtained from the International Atomic Energy Agency (IAEA) Global Network for Isotopes in Precipitation (GNIP) (IAEA/WMO, 2020). We selected a subset of 21 GNIP stations, whose data spanned the isotopic observation period from 1960 to 2018 (Fig. 1) and had <50% of data gaps across the time period. These long-term GNIP stations included inland and continental regions in

Continental stations in Europe and Northern America

GNIP stations located on the American and European continents in the Northern Hemisphere (Groningen, Stuttgart, Vienna, Ankara, Antalya, Gibraltar, Grimsel, Bern and Ottawa) had different climate types (Fig. 1, Fig. 2). While Valentia is an island in the North Atlantic, similarly to Dansgaard (1964) we considered it to be in this group due to the proximity to the European continent. Groningen, Stuttgart, Valentia and Vienna stations are in temperate fully humid climates (Cf) with mean annual

Recommendations

The analysis of the long-term GNIP data series for δ18O in precipitation revealed both complex and diverse isotopic patterns and trends that could not be simplistically related to climate type or “climate change”. This large diversity in long-term global δ18O variations is perhaps better explained by the sensitivity of δ18O to these and other regional and global hydroclimate processes, which are not easily unified in time or space without continuous or higher-frequency isotope monitoring. While

Summary

While longer, more frequent, and complete δ18O (and δ2H) observations are needed, the detected trends, break points with shifts, and polynomial trends are in good agreement with known changes in large scale climate oscillations modes. We suggest that with improved and continuous coordinated long-term monitoring, isotopes in precipitation are an excellent proxy of past, present and even future large-scale hydroclimate processes, such as atmospheric oscillations acting in Northern and Southern

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References (55)

  • L. Baldini et al.

    Spatial variability in the European winter precipitation δ18O-NAO relationship: Implications for reconstructing NAO- mode climate variability in the Holocene

    Geophys. Res. Lett.

    (2008)
  • G.J. Bowen

    Spatial analysis of the intra-annual variation of precipitation isotope ratios and its climatological corollaries

    J. Geophys. Res.-Atmos.

    (2008)
  • J. Brown et al.

    Modelling data δ18O in tropical precipitation and the surface ocean for present-day climate

    J. Geophys. Res.-Atmos.

    (2006)
  • W.S. Cleveland

    LOWESS: a program for smoothing scatter plots by robust locally weighted regression

    Am. Stat.

    (1981)
  • L. Comas-Bru et al.

    The effect of the East Atlantic pattern on the precipitation δ18O-NAO relationship in Europe

    Clim. Dyn.

    (2016)
  • V. Conrad

    Usual formulas for continentality and their limits of validity

    Am. Geophys. Union Trans.

    (1946)
  • W. Dansgaard

    Stable isotopes in precipitation

    Tellus

    (1964)
  • M. Deininger et al.

    North Atlantic Oscillation controls on oxygen and hydrogen isotope gradients in winter precipitation across Europe; implications for paleoclimate studies

    Clim. Past

    (2016)
  • S.R. Esterby

    Review of methods for the detection and estimation of trends with emphasis on water quality applications

    Hydrol. Process.

    (1996)
  • R.D. Field

    Observed and modelled controls on precipitation δ18O over Europe: from local temperature to the Northern Annular Mode

    J. Geophys. Res.

    (2010)
  • K. Froehlich et al.

    Deuterium excess in precipitation of Alpine regions - moisture recycling

    Isot. Environ. Health Stud.

    (2008)
  • J. Gao et al.

    Southern Tibetan Plateau ice core δ18O reflects abrupt shifts in atmospheric circulation in the late 1970s

    Clim. Dyn.

    (2016)
  • J.R. Gat

    Oxygen and hydrogen isotopes in the hydrologic cycle

    Ann. Rev. Earth Planet. Sci.

    (1996)
  • J.R. Gat

    Atmospheric waters

  • S. Goursaud et al.

    Water stable isotope spatio-temporal variability in Antarctica in 1960–2013: observations and simulations from the ECHAM5-wiso atmospheric general circulation model

    Clim. Past

    (2018)
  • M. Hofstätter et al.

    Vb cyclones synchronized with the Arctic‐/North Atlantic Oscillation

    Journal of Geophysical Research: Atmospheres

    (2019)
  • J. Jouzel et al.

    Water isotopes as tools to document oceanic sources of precipitation

    Water Resour. Res.

    (2013)
  • Cited by (17)

    • Nutrient dynamics in temperate European catchments of different land use under changing climate

      2023, Journal of Hydrology: Regional Studies
      Citation Excerpt :

      These meteorological drivers directly affect changes in the snow regime (less persistent snowpack, reduction of the snow water equivalent) in the Czech Republic (Jeníček et al., 2021) and in many European catchments (Fontrodona et al., 2018). Additionally, hydrological changes can be driven by variations in the North Atlantic Oscillation (NAO), which strongly influences European weather and precipitation distribution resulting in the frequency of droughts and floods (IPCC, 2021, Vystavna et al., 2020b, 2021b). Moreover, the flow decline was mostly pronounced in the two anthropogenically impacted catchments (Fig. 2) with less forest coverage (Fig. 1, Table 1), shorter water residence time (Fig. SI-3) and less active water storage (Fig. SI-5).

    • Shallow Quaternary groundwater in the Lake Chad basin is resilient to climate change but requires sustainable management strategy: Results of isotopic investigation

      2022, Science of the Total Environment
      Citation Excerpt :

      The conservative δ18O and δ2H isotopes in precipitation showed prevailing hydroclimate processes that occur before recharging (Stadnyk et al., 2005). A slight enrichment of the isotopic values in time (0.4 ‰ for δ18O and 0.9 ‰ for δ2H) and a decrease in the d-excess at the N'Djamena station is comparable to these observed in Cape Town, South Africa (Vystavna et al., 2020, 2021). This change is related to the air temperature growth intensification of sub-cloud evaporation and the contribution of 18O-enriched vapor due to the evaporation of surface water under the warming conditions (Vystavna et al., 2020, 2021).

    View all citing articles on Scopus
    View full text