It is generally observed that precipitation is gradually depleted in 18O and 2H isotopes as elevation increases (‘altitude’ effect) or when moving inland from seacoasts (‘continental’ effect); the regionally accurate estimation of these large-scale effects is important in isotope hydrological or paleoclimatological applications. Nevertheless, seasonal and spatial differences should be considered. Stable isotope composition of monthly precipitation fallen between January 2016 and December 2018 was studied for selected stations situated along an elevation transect and a continental transect in order to assess the isotopic ‘altitude’ and ‘continental’ effects in modern precipitation across the Adriatic–Pannonian region. Isotopic characteristics argue that the main driver of the apparent vertical depletion of precipitation in heavy stable isotopes is different in summer (raindrop evaporation) and winter (condensation), although, there is no significant difference in the resulting ‘altitude’ effect. Specifically, an ‘altitude’ effect of −1.2‰/km for δ18O and −7.9‰/km for δ2H can be used in modern precipitation across the Adriatic–Pannonian region. Isotopic characteristics of monthly precipitation showed seasonally different patterns and suggest different isotope hydrometeorological regimes along the continental transect. While no significant decrease was found in δ18O data moving inland from the Adriatic from May to August of the year, a clear decreasing trend was found in precipitation fallen during the colder season of the year (October to March) up to a break at ~400 km inland from the Adriatic coast. The estimated mean isotopic ‘continental’ effect for the colder season precipitation is −2.4‰/100 km in δ18O and −20‰/100 km in δ2H. A prevailing influence of the Mediterranean moisture in the colder season is detected up to this breakpoint, while the break in the δ18O data probably reflects the mixture of moisture sources with different isotopic characteristics. A sharp drop in the d-excess (>3‰) at the break in precipitation δ18O trend likely indicates a sudden switch from the Mediterranean moisture domain to additional (mainly Atlantic) influence, while a gradual change in the d-excess values might suggest a gradual increase of the non-Mediterranean moisture contribution along the transect.
Abstract. Tritium (3H) as a constituent of the water molecule is an
important natural tracer in hydrological sciences. The anthropogenic tritium
introduced into the atmosphere unintentionally became an excellent tracer of
processes on a time scale of up to 100 years. A prerequisite for tritium
applications is to know the distribution of tritium activity in
precipitation. Here we present a database of isoscapes derived from 41
stations for amount-weighted annual mean tritium activity in precipitation
for the period 1976 to 2017 on spatially continuous interpolated 1 km×1 km grids for the Adriatic–Pannonian region (called the AP3H_v1 database), with a special focus on post-2010
years, which are not represented by existing global models. Five stations
were used for out-of-sample evaluation of the model performance,
independently confirming its capability of reproducing the spatiotemporal
tritium variability in the region. The AP3H database is capable of
providing reliable spatiotemporal input for hydrogeological application at
any place within Slovenia, Hungary, and their surroundings. Results also show a
decrease in the average spatial representativity of the stations regarding
tritium activity in precipitation from ∼440 km in 1970s, when
bomb tritium still prevailed in precipitation, to ∼235 km in the 2010s. The post-2010 isoscapes can serve as benchmarks for
background tritium activity for the region, helping to determine potential
future local increases in technogenic tritium from these backgrounds. The
gridded tritium isoscape is available in NetCDF-4 at
https://doi.org/10.1594/PANGAEA.896938 (Kern et al., 2019).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.