Abstract
Isotopic composition of precipitation (2H/1H and 18O/16O isotope ratios, tritium content) is nowadays widely used in numerous applications of environmental isotopes—most notably in hydrology, climatology and biogeochemistry. Here we present a long record (44 years) of stable isotope composition and tritium content in monthly precipitation available for the Krakow station (southern Poland). Krakow is the only site in Poland for which long-term record of the isotopic composition of monthly precipitation is available. The tritium data are discussed here in the context of generally declining levels of bomb tritium in the global atmosphere and growing influence of technogenic emissions of this isotope. Two aspects of temporal variability of stable isotope composition of precipitation collected in Krakow are discussed here: (i) seasonality and (ii) interannual changes of δ18O and δ2H signal. Whereas the seasonality of stable isotope signal is generated mainly by seasonally varying the degree of rainout of air masses bringing moisture from the source regions (subtropical Atlantic Ocean) to the centre of the European continent, the North Atlantic Oscillation seems to govern interannual changes of δ18O and δ2H on the decadal timescale. Progressing warming of the local atmosphere, in the order of 1.8 °C in the past four decades, leaves its imprint in stable isotope signal measured in Krakow precipitation; the slope of isotope–temperature relationship is in the order of 0.50‰/°C for δ18O and 3.5‰/°C for δ2H.
Highlights
Isotopic composition of precipitation (2H/1H and 18O/16O isotope ratios, tritium content) is nowadays widely used in applications of environmental isotopes—most notably in hydrology, climatology and biogeochemistry
The record has two parts: (i) the period from January 1975 to December 2018 for which the tritium content in monthly precipitation was measured in Krakow and (ii) the period from January 1961 to January 1975 for which reconstructed values of tritium content in Krakow precipitation are presented
This correlation equation was applied to extrapolate Krakow data back in time from 1974 to 1961. This extrapolation is needed for defining input function of bomb tritium to groundwater systems in applications of this isotope as dating tool in groundwater hydrology (e.g. Maloszewski and Zuber 1996)
Summary
Isotopic composition of precipitation (2H/1H and 18O/16O isotope ratios, tritium content) is nowadays widely used in applications of environmental isotopes—most notably in hydrology, climatology and biogeochemistry. The GNIP database is supplemented by information gathered through national networks monitoring isotopic composition of monthly precipitation on a country scale (e.g. Schürch et al 2003; Liu et al 2014; Tadros et al 2014; Stumpp et al 2014). Transport of tritiated isotopologues of water occurs mainly through discontinuities of the tropopause and as a result of its seasonal ascent. This mechanism generates summer maxima of tritium content in precipitation visible mainly at mid- and high latitudes. The natural tritium content in precipitation varies within the range of 5 to 10 T.U., depending on the location (Rózanski et al 1991; Clark and Fritz 1997)
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