5-7 Proglacial Lake Effects On Downstream Sedimentation In New Zealand’s Southern Alps

Session: Advances in Mountain Hydrology: Connecting Cryosphere, Surface, and Subsurface Processes

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Glacial debris is a productive source of sediment. Glacial melt resulting in the formation of proglacial lakes is an emergent phenomenon of anthropogenic climate change. Globally, there is a lack of data addressing proglacial lake effects on downstream riverine and lacustrine sedimentation. It is unclear whether proglacial lakes as sediment traps restrict glacial debris in downstream river systems. This study evaluated in situ (2004-2023) river turbidity data and Sentinel-2 satellite imagery lake turbidity data (2016-2024) from three river systems in New Zealand’s Southern Alps, a region in which glacial melt is relatively recent. Sentinel-2 imagery was modeled to return Normalized Difference Turbidity Index (NDTI) values for individual lakes. Statistical trend and regression analysis was evaluated between systems and methods of data collection in order to compare both system behavior and relatedness between rivers and lake turbidity. This study found that river system turbidity trends and values are not consistent between lakes and rivers. It is possible that due to lakes and rivers responding differently to sedimentation, lakes are poor predictors of whole watershed turbidity, or that NDTI is an inaccurate form of remote sensing measurement. Glacial watersheds with upstream proglacial lakes were found to be less turbid than those without. Glacial watersheds as a whole were found to be far more turbid than non-glacial watersheds, regardless of extenuating anthropogenic factors. Glacial meltwater signals were detected in both glacial watersheds with and without upstream proglacial lakes. These findings demonstrate proglacial lakes to be effective mitigators of glacial sedimentation in comparison to other glacial watersheds, but not to the extent that glacial debris fluctuations can be fully disrupted.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-6478

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