Lakes, rivers and streams in northern boreal and arctic regions are subject to ongoing changes in water distribution and availability, organic and inorganic chemical loading and processing, and ecosystem structure and composition in response to changing climatic and landscape conditions. Multiple drivers of change include (but are not limited to) warmer temperatures, permafrost thaw, and extended ice-free seasons; altered precipitation and hydrology; and changing flora, fauna, wildfire, and land use. Circumboreal and panarctic understanding of ongoing and projected change in aquatic systems requires detailed process information collected at representative locations, as well as the ability to scale that information spatially across vast unmeasured areas and forward through time. Hence, there is a need to integrate quantitative process-study results and long-term monitoring data with spatially explicit synoptic and remotely sensed information in order to project future conditions. This session welcomes presentations that integrate current and past measurements of aquatic ecosystems with spatial and temporal drivers of change to improve broad scale understanding of current conditions and future trajectories of change in northern inland waters. Related topics include terrestrial release and aquatic biogeochemical processing of carbon, nutrients, suspended solids, and toxins; change in water and materials exports to receiving waters and coastal areas; burial in sediments and atmospheric gas exchange; change inland water surface area and distribution; and change in aquatic community structure and dynamics.
Lead Organizer: Robert Striegl, US Geological Survey, Water Mission Area, Earth System Processes Divsion, Boulder, Colorado, USA (robstriegl@gmail.com)
Co-organizers:
Suzanne Tank, Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada (suzanne.tank@ualberta.ca)
Jan Karlsson, Climate Impacts Research Centre (CIRC), Department of Ecology and Environmental Science, Umeå University, 901 87 Umeå, Sweden (jan.p.karlsson@umu.se)
Presentations
08:30 AM
EVOLVING CONCEPTUAL MODELS OF CLIMATE CHANGE IMPACTS ON AQUATIC BIOGEOCHEMISTRY IN THE ARCTIC (5996)
Tutorial/Invited: Tutorial
Primary Presenter: James McClelland, Marine Biological Laboratory (jmcclelland@mbl.edu)
Concerns about climate change impacts in the Arctic and potential feedbacks to global warming have stimulated an explosion of research in the 21st century. A few basic conceptual models have been instrumental in guiding this research. These models have evolved over time, but legacies from earlier models have, to some extent, also presented barriers to new thinking. This tutorial will consider the conceptual models that have framed research and thinking about climate change impacts on aquatic biogeochemistry in the Arctic as well as permafrost regions more generally. We will explore how early models emphasizing effects of permafrost thaw (particularly active layer deepening) are evolving to embrace multiple factors that influence water chemistry over space and time. These include, but are not limited to, regional differences in geology, vegetation, and soil organic matter; groundwater contributions; thermokarst; shrubification; changing precipitation regimes; and asynchronous shifts in seasonality. We will also address tenacious misconceptions that may be hindering progress and consider steps toward next-generation models that are needed to facilitate future advancements.
08:45 AM
Integrating stream metabolism and biogeochemical fluxes across scales in an Arctic catchment (5829)
Primary Presenter: Ryan Sponseller, Umea University (ryan.sponseller@umu.se)
Climate change is reshaping the face of Arctic landscapes, including patterns of terrestrial productivity, soil processes, and hydrologic fluxes. Such changes have broad consequences for the supply of carbon and nutrients across land-water boundaries. At the same time, the capacity for streams and rivers to respond to these supplies may alter the downstream fate of these elements in the Arctic landscape. Here we synthesize research from the Miellajokka Catchment in northern Sweden to explore the contraints on stream ecosystem metabolism and assess how its variation may influence carbon and nitrogen cycling at multiple spatial and temporal scales. Continuous estimates of gross primary production (GPP) and ecosystem respiration (ER) across this drainage network reveal a diversity of seasonal patterns, which reflect the joint influences of physical constraints and nutrient limitation on rates of stream biological activity. At diel time scales, GPP can in turn create significant biogeochemical signals that are meaningful to broader-scale flux estimates. At seasonal scales, variation in the development of metabolic capacity in streams further governs the extent to which biological processes can influence carbon and nitrogen fluxes downstream. Finally, at interannual scales, differences in the timing and character of spring snowmelt can influence rates of metabolic activity and biogeochemical fluxes throughout the open water season. Collectively, our observations highlight the potential for stream ecosystem processes to influence biogeochemical cycles in a changing Arctic.
09:00 AM
SEASONAL RESPONSE OF WATER QUALITY TO CLIMATIC VARIABILITY IN TWO SMALL HEADWATER CATCHMENTS, MACKENZIE RIVER WATERSHED, NORTHWEST TERRITORIES, CANADA (6107)
Primary Presenter: Erika Hille, Queens University (erika.hille@queensu.ca)
Contemporary climate change and permafrost thaw are influencing the physical hydrology and water quality of Arctic freshwater systems. In the Western Canadian Arctic, thaw-driven mass wasting has set the context for most water quality studies. Few studies have examined aquatic systems not impacted by physical disturbances to the permafrost. As a result, our understanding of how water quality varies spatially (in response to changes in permafrost thaw and terrain conditions) and temporally (in response to seasonal variability in precipitation, thaw, and flow pathways) is limited. The purpose of this investigation is to examine the seasonal chemistry of two small Arctic rivers not influenced by physical permafrost disturbances. Rengleng River and Caribou Creek are situated within a region of continuous permafrost. The recent emergence of late-winter discharge at both sites is unique for small rivers in this region and suggests an increase in groundwater flow contributions. In 2021, water samples were collected up to three times monthly from late-winter to late-summer and analyzed for carbon, nitrogen, phosphorus, and mineral ions. To ascertain the source of winter streamflow, water samples were analyzed for 14C Age. Supplementary water quality data is available for 2019 and 2020. Meteorological, flow, active layer extent, and detailed terrain information is also available. We examine how water quality responds to winter discharge, spring snowmelt, and seasonal fluctuations in active layer thickness, as well as the physical characteristics of each watershed.
09:15 AM
THE IMPORTANCE OF INLAND WATER CO<sub>2<sub>, CH<sub>4<sub>, N<sub>2<sub>O TO SUMMERTIME GREENHOUSE GAS EXCHANGE WITH THE ATMOSPHERE IN ARCTIC TUNDRA LOWLANDS (5903)
Primary Presenter: Melanie Martyn Rosco, Vrije Universiteit Amsterdam (m.martynrosco@vu.nl)
Inland waters in Arctic landscapes act as conduits of terrestrial material by transporting and processing it, subsequently exchanging the greenhouse gases (GHG) carbon dioxide (CO<sub>2</sub>), methane (CH<sub>4</sub>) and nitrous oxide (N<sub>2</sub>O) with the atmosphere. To quantify the role of inland water emissions in the Arctic GHG budget, it is necessary to assess their emissions in relation to the terrestrial sink capacity. We present measurements of dissolved CO<sub>2</sub>, CH<sub>4</sub> and N<sub>2</sub>O from lake, pond and low order fluvial systems across two summers (2016-2017) in the Indigirka River lowlands. During May-July 2017, the region experienced a large flood of which we captured the tail end. Using remote sensing images to up-scale inland water emissions to an area of approximately 18 km<sup>2</sup> we calculated combined carbon (C) emissions, CO<sub>2</sub>-C and diffusive CH<sub>4</sub>-C. Considering N<sub>2</sub>O emissions in terms of their radiative forcing showed that they were negligible compared to CO<sub>2</sub> and CH<sub>4</sub> emissions. Our results shows that in the northeast Siberian Arctic tundra, CO<sub>2</sub> and CH<sub>4</sub> emissions from inland waters are a significant component (potentially up to 25 %) of the landscape C exchange with the atmosphere. Accurately integrating these into regional carbon budgets is essential for forecasting, climate-impact-assessment and to better constrain the feedback to climate warming.
09:30 AM
GREENHOUSE GAS PRODUCTION IN LAKES AS INFLUENCED BY THEIR TERRESTRIAL ENVIRONMENT ACROSS A NORTH-SOUTH GRADIENT: FROM TUNDRA THROUGH BOREAL FOREST TO PRAIRIES (5566)
Primary Presenter: Vilmantas Prėskienis, University of Quebec in Chicoutimi (preskienis@yahoo.com)
Boreal forests of Western Canada are bordered by two treelines (southern at 53°N, northern at 62°N), both of which are moving northwards with the ongoing climate change. This study of organic matter cycling in 23 lakes crossing 6 ecological regions (from tundra to Prairies) is a part of a multidisciplinary project bringing together the Dene and Inuit communities with laboratories specialising in biogeochemistry and palaeolimnology. To identify differences in greenhouse gas (GHG) production across these ecoregions, limnological data collected in situ were complimented by anoxic incubation experiments, measuring CO2 and CH4 production rates. Lakes with deciduous forest catchments (transition from boreal forest to Prairies) had the highest GHG production rates, possibly caused by a combination of more labile terrestrial organic matter inputs and warmer temperatures (than the lakes within coniferous forests and tundra), and a tendency to stratification (relative to more open grassland lakes). Overall, the southern lakes had higher productivity and higher CH4 concentrations, while surface N2O concentrations were higher in northern lakes. Surprisingly, northern boreal lakes were also prone to eutrophication – likely as a consequence of forest fires, increasingly common in these areas. Warmer water temperatures, stronger stratification, northward migration of deciduous trees and Arctic greening will likely lead to increased primary production and accumulation of GHG, followed by potentially deteriorating water quality with negative impacts on fish and northern communities.
09:45 AM
An innovative outlook on the interplay between lake methane emissions and their response to climate (6446)
Primary Presenter: Cristian Gudasz, Umeå University (cristian.gudasz@umu.se)
Methane emissions from lakes play a significant role in global fluxes and are essential to understanding climate sensitivity and feedback. However, uncertainties in quantifying this contribution still persist. Complex interactions between lake hypsography, climate, and biogeochemistry largely govern methane emissions from lakes. These interactions make it difficult to predict even at the individual lake scale due to the strong nonlinear nature of these relationships. Furthermore, well established understanding at individual lake scales does not necessarily translate similarly at Earth System scales asdrivers that control ecological variation in lakes are different from local to continental scales. We use coupled climate and dynamic process-based models, along with lake hypsography, to overcome this hurdle. The models describe lake physics and basic biogeochemistry, and allow us to resolve daily and yearly methane diffusive and ebullitive emission fluxes encompassing baseline, average and maximum range conditions in millions of lakes worldwide. Our analysis involved the examination of methane emissions and its apparent temperature sensitivity, using spatial and temporal aggregation, globaly and across key climatic zones. Our approach reveals relationships and patterns that may not be apparent from statistical analysis alone and helps address fundamental questions on the role of lakes and sensitivity to climate at Earth System scales.
SS021A Responses of Boreal and Arctic Inland Waters to Changing Climatic and Landscape Conditions
Description
Time: 8:30 AM
Date: 7/6/2023
Room: Sala Menorca B