Abstract
Speleothems deposited from cave drip waters retain, in their calcite lattice, isotopic records of past environmental changes. Among other proxies, δ18O is recognized as very useful for this purpose, but its accurate interpretation depends on understanding the relationship between precipitation and drip water δ18O, a relationship controlled by climatic settings. We analyzed water isotope data of 17 caves from different latitudes and altitudes in relatively small but diverse Croatian karst regions in order to distinguish the dominant influences. Drip water δ18O in colder caves generally shows a greater resemblance to the amount-weighted mean of precipitation δ18O compared to warmer sites, where evaporation plays an important role. However, during glacial periods, today’s ‘warm’ sites were cold, changing the cave characteristics and precipitation δ18O transmission patterns. Superimposed on these settings, each cave has site-specific features, such as morphology (descending or ascending passages), altitude and infiltration elevation, (micro) location (rain shadow or seaward orientation), aquifer architecture (responsible for the drip water homogenization) and cave atmosphere (governing equilibrium or kinetic fractionation). This necessitates an individual approach and thorough monitoring for best comprehension.
Highlights
Understanding the mechanisms and extent of past environmental changes is a key consideration for predicting global climate changes
We investigated the dominant factors controlling the transmission of the isotopic signal from precipitation to cave drip water in different climate settings, and how this information can be
Nova Grgosova (NG) cave; (b) Delnice station representing continental settings with orographic effect on LOK cave; (c) Zavižan station for high-altitude conditions with a strong orographic effect (ZB, Velebita Cave System (VEL), SIR, Lukina jama (LUK)); (d) Gračac station as representative for continental sites with a rain-shadow effect (DB, SIR, LUK); (d) Gračac station as representative for continental sites with a rain-shadow effect (DB, GB, DC caves); and (e) Vela Sestrica station representing conditions of low-altitude caves located on GB, DC caves); and (e) Vela Sestrica station representing conditions of low-altitude caves located on the islands and along the coast (MOD, Strašna peć (SP), Medvjeda špilja (MED), VRD, Kraljičina Spilja (KRA), MML, VML)
Summary
Understanding the mechanisms and extent of past environmental changes is a key consideration for predicting global climate changes. Establishing cave hydroclimate monitoring is critical to assess variability in these two parameters It is not always the case [8], caves are usually considered environments with stable microclimate parameters, with relative humidity (RH) close to 100%, and air temperature equal to the surface mean annual air temperature (MAAT), without seasonal variations. When such conditions are met in particular parts of the cave, underground environmental changes respond to long-term climate changes and are recorded in the isotopic composition of slow-growing speleothems. We investigated the dominant factors controlling the transmission of the isotopic signal from precipitation to cave drip water in different climate settings, and how this information can be. 4 inrange [45]).mountains (see Figure 4 in [45])
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