This project explored the feedback of Arctic warming and the ongoing loss of sea ice—phenomena collectively known as Arctic Amplification—and North Eurasian hydrology. Specifically, it aimed to estimate long-term variability in freshwater flow and heat flux from large river basins to the Arctic, despite sparse, short, and incomplete hydrological observations. A collaborative effort between two universities envisioned a new tool to support multidisciplinary research community in this area. The goal was to enable researchers to explore historical hydrological dynamics, understand their context within climate change, and assess their relationship with Arctic Amplification. We approached to connect spatial networks of tree-ring proxies, water balance modeling and advanced regression-based reconstruction methods.  The result was the creation of the Tree-Ring Integrated System for Hydrology (TRISH), a web-based platform that integrates global water balance model (NH-WBM) simulating variables such as discharge, runoff, precipitation, soil moisture, and water temperature, an interactive GIS mapping system, and statistical algorithms for diagnostic tree-ring time series.

            To design and test TRISH, we sampled tree rings from the Yenisei River basin and performed spatial reconstructions of its flow rates. To implement the tree-ring hydrologic modeling in cold climates, the project enhanced the NH-WBM simulations via updating instrumental hydrological observations and introducing new modules for snowmelt, deep groundwater, glacier runoff, and permafrost. Tree-ring reconstructions of the Yenisei River’s flow over the past 250-300 years revealed charges in seasonal and spatial discharge patterns that were more complex and heterogeneous than those suggested by instrumental data. Notably, we observed significant variations in winter discharge, especially in the upper reaches. Our findings indicate a remarkable increase (up to 70%) in winter flow at the Yenisei River headwaters, likely driven by permafrost degradation and rerouted subsurface water, which is exacerbated by both warming temperatures and intensified forest fires. The reconstruction also identified periods of abnormally high discharge during the 1750-1840s and 1980s-2020s, contrasting with a more stable low flow regime between 1850 and 1950. In contrast to the upper reaches, seasonal flow fluctuations were less pronounced in the lower reaches, although the long-term trends in annual flow were similar across the basin.

            These findings demonstrate the significant potential of integrating tree-ring data with modeled water balance information to assess runoff and streamflow trends in Siberian river basins—the largest freshwater contributors to the Arctic Ocean. This is particularly valuable for regions with limited instrumental discharge data and where natural flow regimes have been significantly altered by industrial activities. The tool also has an important application for water management, especially for transboundary waters and agriculture. For instance, the TRISH tool tested to quantify long-term trends in soil moisture, flow rates, and runoff within specific basins or administrative divisions.

            The project provided training for an M.S. student in dendrochronology, quantitative wood anatomy, and scientific coding, along with support for three B.S. students and two high school science teachers, all of whom contributed to tree-ring data processing. The results of the project have been published in open-access journals, including Environmental Research Letters, AMS Earth Interactions, Trees, and Environmental Modeling and Software. The tree-ring records, updated water temperature data, computational codes, and WBM-simulated hydrological variables generated during this study are publicly available through the NSF Arctic Data Center. The TRISH tool is fully operational and accessible at https://trish.sr.unh.edu/. Its capacity, as well as discussion on the feedback of Arctic amplification and midlatitude hydrology, has been widely disseminated through media, public lectures, seminars, outreach events, international conferences, and a specialized AGU workshop.

Last Modified: 07/16/2025
Modified by: Alexander Shiklomanov