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Hydrological Sciences

Featured catchment series: The North is not forgotten!

Featured catchment series: The North is not forgotten!

This is the first post of “Featured Catchment”, a series of posts in the HS Blog that present experimental catchments across Europe and beyond. Here, the authors of the posts will explain the main characteristics (e.g., climate, geology, topography, land use) of their catchments, why hydrologic research is important in their study areas, describe the applied methodologies (field instrumentation and hydrological models), main findings and both current and future challenges.

The North is not forgotten! Ecohydrology at the subarctic Pallas research supersite

A unique insight to Arctic hydrology

A special character of the Pallas catchment comes from its northern location at 68°N, about 130 km north from the Arctic Circle in subarctic Finland. To our knowledge Pallas is the most northern research catchment not influenced by permafrost, which makes it a possible analog to permafrost catchments of the future once they lose their frozen soil base. Recent unprecedented rates of environmental change in the Arctic has alerted the scientific community, but at the same time the number of active high-latitude research catchments has been in persistent decline. To answer the call for hydrological research of the north, we started our ecohydrology work at the Pallas in 2014.

Site introduction aboard a drone; view of the snowy landscape with key hydrologically relevant numbers.

Northern Stable Isotope Monitoring program

Northern lights above the lodging facilities of Parks and Wildlife Finland keep the spirits high between days of cold field work.

We look at northern ecohydrology through a lens of a comprehensive northern stable water isotope monitoring program. Our mission is to get a detailed overview of the full Arctic water cycle, from oceans to rainfall and the subsequent partitioning between vegetation, groundwater and headwater streams, by using stable isotopes of water (2H, 18O).

Specifically, the Northern Stable Isotope Monitoring program at the Pallas catchments consists of:

  • continuous high-frequency in-situ stable water isotope monitoring of atmospheric water vapour and stream water (Academy of Finland funded postdoctoral scientist Hannah Bailey and by UArctic Chairship postdoctoral scientist Dr. Kaisa-Riita Mustonen)
  • extensive snow stable water isotope monitoring program to measure spatial and temporal variability in the isotopic composition of snowpack and snowmelt (PhD project of Kashif Noor)
  • soil water flux isotope measurements using lysimeters, soil coring, and experimental tracer approaches to characterize the water movement in the shallow subsurface (PhD project of Filip Muhic)
  • Water isotope sampling from plants to better understand the role of vegetation in the short growing season of the northern water cycle.

Hydrological collaborations with interdisciplinary environmental science

Example of a monitoring station on a peatland in the valley bottom.

Another special feature of the site is the interdisciplinary environmental research carried out by five Finnish national research institutes (FMI, LUKE, SYKE and GTK) in the Pallas region. Pallas comprises one of the most important climate and ecosystem research station in the circumpolar region. The extremely high-quality atmospheric water and greenhouse gas (GHG) measurements in the area (four Eddy-covariance flux stations within 10km2 and a high-precision atmospheric concentration measurement station both operated by FMI) compliments the hydrological research activities. Ongoing collaborative research projects aim to:

  • Investigate the influence of soil water condition in GHG exchange and carbon balance from boreal forest soils (FMI, Dr. Annalea Lohila)
  • Monitor carbon and GHG emission from headwater streams to study the influence of instream microbiology and hydrological connectivity of the stream and the landscape (University of Oulu, Dr. Jussi Jyväsjärvi)
  • Understand how hydrology and soil microbes are controlling soil GHG production potential in subarctic landscape (FMI, LUKE and University of Helsinki)
  • Monitor snow, vegetation and soil moisture by using drones (PhD project of Leo-Juhani Meriö, University of Eastern Finland and Dr. Timo Kumpula)
  • Determine the atmospheric fallout derived black carbon in snow and melting waters (Dr. Outi Meinander, FMI)

Ongoing work and current challenges

Unravelling the complex relationship of water and carbon in the North
Where can we find the hotspots for hydrology and biogeochemical activity? The usual suspects are the stream and its riparian zone, and groundwater exfiltration areas, such as springs and seepages. We hypothesize that better understanding of hydrological flow path activation in space and in time will help explain the carbon and nitrogen dynamics and GHG emissions from northern landscapes.

Conceptual idea of key processes and fluxes linking the water and carbon cycle in the Pallas study catchment.

Understanding our data through numerical modelling
Our long-term objective is to develop a numerical model to simulate the hydrological (aided by stable isotopes of water) and carbon cycle in the north. We argue that numerical modelling based on extensive and long-term biogeochemistry and hydrometric datasets is the best available tool for data integration across our collaborative disciplines in hydrology, ecology, and atmospheric sciences. For example, the PhD project of Anna Jaros is using integrated hydrological modelling to study the role of groundwater in sustaining peatland ecosystem.

Snow and ice – hydrological and practical challenges

We like to dig a bit deeper – working on pits to measure snow density and sample snow for water isotopes.

We need to keep up the struggle with the harsh cold northern environment. How do instruments survive and how do we get samples taken in the dead of the winter, when temperatures are below -35 °C and amount of daylight is minimal? Winter conditions prevail for more than half of the year, and we need to be able to monitor that half too to understand the system as a whole. We currently lack understanding of key processes during winter, such as hydrological and biogeochemical activity during winter below the snow and ice cover, influence of seasonal frost on hydrological partitioning of snowmelt, and isotope hydrology of snowpack and snowmelt.

Time lapse of spring 2018 snowmelt at stream gauging station. The highest flows in the catchment result from spring snowmelt, and we see how the peak flow occurs at very late stages of snowmelt. What happens in between the snowmelt initiation and the peak flow? Where is water stored, what parts of the catchment contribute to streamflow?

Got interested? Please get in touch to start a collaboration in exploring northern latitudes with Arctic attitudes! www.oulu.fi/water/pallas

Funded research projects:

– Pallas is a key site of Academy of Finland funded Arctic Interactions (ArcI Profi4) strategic research profile of the University of Oulu, led by Prof Björn Klöve
– High-resolution Arctic water isotope (δ18O & δ2H) cycles record and reveal sea ice-atmosphere-hydrologic (SIAH) interactions. Academy of Finland award, Jeffrey Welker.
– Pan-Arctic Precipitation Isotope Network (PAPIN), EU INTERACT award, led by Jeffrey Welker.
– What happens to snow when it melts? Academy of Finland Postdoctoral Researcher grant, Pertti Ala-aho.
– What is the role of other-than-peaty-soils for the catchment-scale methane balance and what are the hydrological linkages to CH4 production-oxidation processes. Academy of Finland project UPFORMET, PI Annalea Lohila
– Supersite for Arctic environmental research – a new study area for ​​Arctic hydrology, Maa- ja Vesitekniikan tuki ry, PI Hannu Marttila
– Surface-groundwater interaction in boreal peatland-esker systems: conceptualization of hydrogeological process, integrated numerical modelling and assessment of climate change. Kvantum institute, Strategic research project of the University of Oulu, PI Prof Bjørn Kløve
– Interactions between groundwaters from bedrock and eskers in Northern areas. K. H. Renlund Foundation, PI Hannu Marttila

Edited by Matthias Sprenger

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Guest author Pertti Ala-aho is a Postdoc at University of Oulu and investigates the environmental importance of snowmelt water in the Arctic and other snow-influenced regions. He gained his PhD in 2014, and has since worked in international collaborations in Alaska, Siberia, Canada, Scotland, and Scandinavia. Ala-aho combines numerical modeling with stable water isotope tracer techniques to track snow along its journey from origin (oceans) to snowmelt and its role as ecosystem water source.

 

Guest author Hannu Marttila is a Senior Research Fellow and leading Northern Hydrology group at Water, Energy and Environmental Research Unit in Oulu. His research focuses on hydrological processes and catchment management issues in northern landscapes with strong cross-disciplinary work across science fields. Marttila has been participating and managed several Academy of Finland, EU and foundation based projects. He is a chairman in Hydrology division at Finnish Water Association and hydrology subject editor for Boreal Environmental Research Journal.

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