Subarctic catchment water storage and carbon cycling – Leading the way for future studies using integrated datasets at Pallas, Finland

Hannu Marttila,Jussi Vuorenmaa,Anssi Rauhala,Annalea Lohila,Timo Kumpula,Leo‐Juhani Meriö,Mika Aurela,Anna Autio,Anton Kuzmin,Kashif Noor,Danny Croghan,Jeffrey M Welker,Valtteri Hyöky,Timo Penttilä,Pasi Korpelainen,Filip Muhic,Pertti Ala‐Aho,Hannah Bailey,E S Klein ,Kaisa‐Riikka Mustonen

doi:10.1002/hyp.14350

Abstract

AbstractSubarctic ecohydrological processes are changing rapidly, but detailed and integrated ecohydrological investigations are not as widespread as necessary. We introduce an integrated research catchment site (Pallas) for atmosphere, ecosystems, and ecohydrology studies in subarctic conditions in Finland that can be used for a new set of comparative catchment investigations. The Pallas site provides unique observational data and high‐intensity field measurement datasets over long periods. The infrastructure for atmosphere‐ to landscape‐scale research in ecosystem processes in a subarctic landscape has recently been complemented with detailed ecohydrological measurements. We identify three dominant processes in subarctic ecohydrology: (a) strong seasonality drives ecohydrological regimes, (b) limited dynamic storage causes rapid stream response to water inputs (snowmelt and intensive storms), and (c) hydrological state of the system regulates catchment‐scale dissolved carbon dynamics and greenhouse (GHG) fluxes. Surface water and groundwater interactions play an important role in regulating catchment‐scale carbon balances and ecosystem respiration within subarctic peatlands, particularly their spatial variability in the landscape. Based on our observations from Pallas, we highlight key research gaps in subarctic ecohydrology and propose several ways forward. We also demonstrate that the Pallas catchment meets the need for sustaining and pushing the boundaries of critical long‐term integrated ecohydrological research in high‐latitude environments.

Highlights

High-latitude areas are facing an unprecedented transition in the near future as warming air, precipitation changes, and sea ice cover reductions continue to drive broad-scale and long-term change across the northern areas (Bailey et al, 2021; Bekryaev et al, 2010; Bintanja & Selten, 2014; Buchwall et al, 2020; Cohen et al, 2014; Ernakovich et al, 2014; Lee et al, 2011; Liston & Hiemstra, 2011; Neumann et al, 2019)
In the Pallas area, the observed seasonal variability in precipitation δ18O values ranges between À23‰ and À8‰, and in-stream water δ18O values range between À14‰ and À10‰ (Figure 2), and exhibit strong seasonal fluctuation and variation along the stream continuum (Figure 3)
Spring isotope values show smaller variability compared with groundwater samples, indicating hydrological mixing along the hillslope transect from recharge to discharge

Summary

Introduction

High-latitude areas are facing an unprecedented transition in the near future as warming air, precipitation changes, and sea ice cover reductions continue to drive broad-scale and long-term change across the northern areas (Bailey et al, 2021; Bekryaev et al, 2010; Bintanja & Selten, 2014; Buchwall et al, 2020; Cohen et al, 2014; Ernakovich et al, 2014; Lee et al, 2011; Liston & Hiemstra, 2011; Neumann et al, 2019). Ecosystem-atmosphere GHG exchange and meteorological conditions (precipitation, air temperature, potential evaporation, incoming and reflected solar radiation) are measured by the FMI at the Kenttärova forest site, Lompolojänkkä mire, and Pallasjärvi lake shore within the Pallas catchment, using eddy covariance flux stations (Table 1).

Results

Conclusion