4. Research findings and applications
To our knowledge, CHRS is the only hydrological research site situated
above the tree timberline (i.e., >3,000-3,100 m asl) in the
Central American and Caribbean region. The Central American region is
transected by a NW–SE mountain range that divides the region into the
Caribbean and Pacific slopes with similar precipitation regimes
(Sánchez-Murillo et al., 2020a). The unique geographic location of Costa
Rica within this mountainous region, with moisture inputs from the
Caribbean Sea (windward) and the Pacific Ocean (complex leeward
topography), offers an ideal scenario for the use water stable isotopes
to develop hydrological research (Sánchez-Murillo et al., 2020b).
Combined analysis of air mass back trajectories and the temporal
precipitation isotopic variations for CHRS revealed the effective
contribution of maritime moisture from the Caribbean Sea (90%
frequency) and the Pacific Ocean (10% frequency), with the preferential
contribution from the Caribbean due the influence of the north‐east
trade winds travelling over the central and south‐eastern Caribbean Sea
towards CHRS (Fig 2b,c; Esquivel-Hernández et al., 2019). CHRS data are
also key to identify inputs from the central Pacific Ocean and local
evapotranspiration fluxes. Overall, as water vapour encounters the main
mountain range, orographic distillation and convergence increase,
resulting in depleted precipitation arriving from the Pacific domain
(Fig 2b; Sanchez-Murillo et al., 2020a). The lesser contribution of
recycled water vapour arriving at CHRS is indicated by thed -excess variations in precipitation (d- excess
values>10‰, Fig. 2c).
The first isotopic characterization of the surface water system of CHRS
indicate that the evaporation conditions in the glacial lakes are highly
influenced by input from precipitation that is in isotopic equilibrium
with local water vapour, yielding low evaporation to inflow ratios
(< 20%, Esquivel-Hernández et al., 2018). Due to their
position near the equator and high elevation, lake water temperature of
Lake Ditkevi shows seasonal variations but weak thermal stratification
(Fig. 2a). Overall, the attenuation effect observed in the isotopic
composition (δ18O) and d -excess of lake water
most likely resulted from the relatively long residence times of
precipitation, stream, and subsurface water (Fig. 2b,c). However, when
compared to precipitation, lake and surface water reflects the
evaporation effects as the corresponding evaporation lines (ELs) diverge
from the local meteoric water line (LMWL) of the study region (Fig. 3).
Therefore, because of the isotopic enrichment, the slopes of the ELs
fall between the slope of the LMWL and the slope of local evaporation
line (LEL) calculated using pan evaporation data (Fig.3;
Esquivel-Hernández et al., 2018).
The intensity of sources or sinks of methane remain critically
understudied in high elevation biomes and scarce data are currently
available in the literature for the neotropical Páramo ecosystems. CHRS
meteorological data were essential to identify key drivers of methane
fluxes in soils of the Chirripó National Park. Overall, the identified
soil and vegetation gradients revealed that sites without
drainage-impeding soil layers or with the facilitating presence of
vigorous Chusquea vegetation led to relatively stronger sinks of
methane as compared to fields with wetter, less aerated soils (Chai et
al., 2020). CHRS data has also served as baseline information to improve
the limited paleoclimate data in Central America and to provide reliable
estimates of hydroclimate and environmental change in this region (Wu et
al., 2019a,b).