Accounting for Winter Warming Events in the Ecosystem Model LPJ‐GUESS: Evaluation and Outlook
In: Journal of Geophysical Research - Biogeosciences, Jg. 129 (2024-03-01), Heft 3
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Zugriff:
Winter warming events (WWEs) are short‐lasting events of unusually warm weather, occasionally combined with rainfall, which can cause severe ecosystem impacts by altering ground temperatures and water fluxes. Despite their importance, how large‐scale ecosystem models perform in depicting the impacts of WWEs remain largely unknown. The frequency and intensity of WWEs will likely increase further in the future, making it necessary to understand their potential impacts on high‐latitude ecosystems. In this study, we evaluated the ability of the dynamic ecosystem model Lund‐Potsdam‐Jena General Ecosystem Simulator (LPJ‐GUESS) to represent the responses of subarctic ecosystems to future WWEs, and identified model gaps hindering more accurate estimates of these responses. In response to WWEs, the model simulated substantial ground cooling (up to 2°C in winter) due to reduced snow depth (insulation), with rain on snow (ROS) exerting a marginal influence on the ground temperature responses: these modeled responses are in apparent contradiction with the strong ground warming effect of ROS reported in most observational studies. The simulated ground cooling led to changes in biogeochemical fluxes that were substantial and often comparable in magnitude (but often opposite in direction) to those from altered winter climatologies. The mismatch between the modeled and the observed ground temperature responses to WWEs highlights LPJ‐GUESS's current limitations in realistically simulating some of the effects of WWEs. These limitations likely stem from the (a) absence of a surface energy balance, (b) lack of snow‐vegetation interactions, (c) daily time‐step, and (d) simplistic water retention scheme in LPJ‐GUESS. Winter warming events (WWEs) are episodes of exceptionally warm weather lasting from hours to days and often occur in combination with rainfall. The combined effect of multiple processes triggered by WWEs (involving, for example, changes in snow depth, and heat exchanges between air, rain and meltwater, and soils) results in profound changes in ground temperatures and water fluxes, which many ecosystem processes depend on (vegetation dynamics, organic matter decomposition, etc). WWEs will intensify in the future as the climate continues to warm. However, we do not know how well‐represented the effects of WWEs are in the ecosystem models used to study future changes in arctic ecosystems, which tend to oversimplify some complex physical processes. This study used a widely used ecosystem model, Lund‐Potsdam‐Jena General Ecosystem Simulator, to evaluate how well the model can simulate future ecosystem responses to more frequent and intense WWEs. The modeled ecosystem responses we observed were large, but contradicted field measurements. This can cause large uncertainties in predicting future changes in arctic ecosystems. We identified the processes lacking in the model that, if implemented, would likely improve the predictions of future ecosystem changes in response to climate change. We thoroughly evaluated, for the first time, the impacts of winter warming events (WWEs) on different ecosystem processes in Lund‐Potsdam‐Jena General Ecosystem Simulator (LPJ‐GUESS)We highlight LPJ‐GUESS's limitations in simulating some observed responses to WWE, adding uncertainties to predictions of ecosystem changesThe limitations stem from the lack of energy balance and snow‐vegetation interactions, daily time‐step, and simple water retention scheme We thoroughly evaluated, for the first time, the impacts of winter warming events (WWEs) on different ecosystem processes in Lund‐Potsdam‐Jena General Ecosystem Simulator (LPJ‐GUESS) We highlight LPJ‐GUESS's limitations in simulating some observed responses to WWE, adding uncertainties to predictions of ecosystem changes The limitations stem from the lack of energy balance and snow‐vegetation interactions, daily time‐step, and simple water retention scheme
Titel: |
Accounting for Winter Warming Events in the Ecosystem Model LPJ‐GUESS: Evaluation and Outlook
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Autor/in / Beteiligte Person: | Pascual, D. ; Johansson, M. ; Pongracz, A. ; Tang, J. |
Link: | |
Zeitschrift: | Journal of Geophysical Research - Biogeosciences, Jg. 129 (2024-03-01), Heft 3 |
Veröffentlichung: | 2024 |
Medientyp: | serialPeriodical |
ISSN: | 2169-8953 (print) ; 2169-8961 (print) |
DOI: | 10.1029/2023JG007464 |
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