Oladapo et al. (2026) Factors affecting the preservation of the isotopic fingerprint of glacial meltwater in mountain groundwater systems

Identification

• Journal: Journal of Hydrology
• Year: 2026
• Date: 2026-01-23
• Authors: Ayobami Oladapo, M. D. Frisbee, Ann Pearson, Darryl E. Granger
• DOI: 10.1016/j.jhydrol.2026.134990

Research Groups

• Dept. of Earth, Atmospheric, and Planetary Sciences, Purdue University, USA
• Department of Plant and Microbial Biology and The BioTechnology Institute, College of Biological Sciences, University of Minnesota, Twin Cities, USA

Short Summary

This study rigorously investigates factors affecting the preservation of glacial meltwater's isotopic fingerprint in mountain groundwater systems using isotopic tracers and a novel englacial mixing model. It reveals that hydrostratigraphic controls, slope aspect, and englacial mixing processes significantly influence this preservation, with distinct outcomes observed in Glacier National Park and Mount Hood.

Objective

• Does slope aspect affect the preservation of the isotopic fingerprint of glacial meltwater in groundwater?
• Is the isotopic fingerprint of glacial meltwater preserved in groundwater with increasing distance from the glacier?

Study Configuration

• Spatial Scale: Glacier National Park (GNP) and Mount Hood (MH), USA.
• Temporal Scale: Contemporary hydrological processes, with context of climate change impacts since the 1960s and 1970s.

Methodology and Data

• Models used: Stable isotopic mixing model, Englacial Mixing Model (EMM).
• Data sources: Field measurements of tritium (3H), chlorine-36 ratios (36Cl/Cl), and strontium-isotope ratios (87Sr/86Sr) from groundwater.

Main Results

• In Glacier National Park (GNP), slope aspect relationships are obscured by hydrostratigraphic controls on groundwater flow, and flowpath connectivity is limited by low-permeability rocks. The isotopic fingerprint of glacial meltwater is preserved by 36Cl/Cl but not 3H.
• In Mount Hood (MH), springs emerging from north-facing slopes preserve the isotopic fingerprint of glacial meltwater, while springs from south-facing slopes show stronger evidence for flowpath connectivity across spatial scales.
• An Englacial Mixing Model (EMM) is proposed, indicating that the isotopic fingerprint of subglacial flow and groundwater recharge is a complex mixture of glacial meltwater, snowmelt, and rain, strongly dependent on englacial mixing processes and the stage of glacial retreat.
• The EMM suggests that the isotopic fingerprint of springs in GNP is becoming increasingly influenced by seasonal snowmelt relative to glacial meltwater, whereas in MH, it is a dynamic mixture, but glacial meltwater is still preserved in some springs.

Contributions

• Provides the first rigorous investigation into factors affecting the preservation of glacial meltwater's isotopic fingerprint in mountain groundwater systems.
• Introduces the Englacial Mixing Model (EMM) to conceptualize the complex mixing of water sources (glacial meltwater, snowmelt, rain) within glaciers and their contribution to groundwater recharge.
• Demonstrates the varying influence of hydrostratigraphic controls, slope aspect, and englacial mixing on isotopic preservation across different alpine environments.
• Highlights the dynamic nature of groundwater recharge sources in response to glacial retreat and climate change.

Funding

Not specified in the provided text.

Citation

@article{Oladapo2026Factors,
  author = {Oladapo, Ayobami and Frisbee, M. D. and Pearson, Ann and Granger, Darryl E.},
  title = {Factors affecting the preservation of the isotopic fingerprint of glacial meltwater in mountain groundwater systems},
  journal = {Journal of Hydrology},
  year = {2026},
  doi = {10.1016/j.jhydrol.2026.134990},
  url = {https://doi.org/10.1016/j.jhydrol.2026.134990}
}