| 1. |
- Akperov, Mirseid, et al.
(författare)
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Responses of Arctic cyclones to biogeophysical feedbacks under future warming scenarios in a regional Earth system model
- 2021
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9318 .- 1748-9326. ; 16:6
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Tidskriftsartikel (refereegranskat)abstract
- Arctic cyclones, as a prevalent feature in the coupled dynamics of the Arctic climate system, have large impacts on the atmospheric transport of heat and moisture and deformation and drifting of sea ice. Previous studies based on historical and future simulations with climate models suggest that Arctic cyclogenesis is affected by the Arctic amplification of global warming, for instance, a growing land-sea thermal contrast. We thus hypothesize that biogeophysical feedbacks (BF) over the land, here mainly referring to the albedo-induced warming in spring and evaporative cooling in summer, may have the potential to significantly change cyclone activity in the Arctic. Based on a regional Earth system model (RCA-GUESS) which couples a dynamic vegetation model and a regional atmospheric model and an algorithm of cyclone detection and tracking, this study assesses for the first time the impacts of BF on the characteristics of Arctic cyclones under three IPCC Representative Concentration Pathways scenarios (i.e. RCP2.6, RCP4.5 and RCP8.5). Our analysis focuses on the spring- and summer time periods, since previous studies showed BF are the most pronounced in these seasons. We find that BF induced by changes in surface heat fluxes lead to changes in land-sea thermal contrast and atmospheric stability. This, in turn, noticeably changes the atmospheric baroclinicity and, thus, leads to a change of cyclone activity in the Arctic, in particular to the increase of cyclone frequency over the Arctic Ocean in spring. This study highlights the importance of accounting for BF in the prediction of Arctic cyclones and the role of circulation in the Arctic regional Earth system.
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| 2. |
- Wu, Minchao, et al.
(författare)
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Impacts of land use on climate and ecosystem productivity over the Amazon and the South American continent
- 2017
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 12:5
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Tidskriftsartikel (refereegranskat)abstract
- The Amazon basin is characterized by a strong interplay between the atmosphere and vegetation. Anthropogenic land use and land cover change (LULCC) affects vegetation and the exchange of energy and water with the atmosphere. Here we have assessed potential LULCC impacts on climate and natural vegetation dynamics over South America with a regional Earth system model that also accounts for vegetation dynamics. The biophysical and biogeochemical impacts from LULCC were addressed with two simulations over the CORDEX-South America domain. The results show that LULCC imposes local and remote influences on South American climate. These include significant local warming over the LULCC-affected area, changes in circulation patterns over the Amazon basin during the dry season, and an intensified hydrological cycle over much of the LULCC-affected area during the wet season. These changes affect the natural vegetation productivity which shows contrasting and significant changes between northwestern (around 10% increase) and southeastern (up to 10% decrease) parts of the Amazon basin caused by mesoscale circulation changes during the dry season, and increased productivity in parts of the LULCC-affected areas. We conclude that ongoing deforestation around the fringes of the Amazon could impact pristine forest by changing mesoscale circulation patterns, amplifying the degradation of natural vegetation caused by direct, local impacts of land use activities.
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| 3. |
- Zhang, Wenxin, et al.
(författare)
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Tundra shrubification and tree-line advance amplify arctic climate warming : results from an individual-based dynamic vegetation model
- 2013
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 8:3
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Tidskriftsartikel (refereegranskat)abstract
- One major challenge to the improvement of regional climate scenarios for the northern high latitudes is to understand land surface feedbacks associated with vegetation shifts and ecosystem biogeochemical cycling. We employed a customized, Arctic version of the individual-based dynamic vegetation model LPJ-GUESS to simulate the dynamics of upland and wetland ecosystems under a regional climate model-downscaled future climate projection for the Arctic and Subarctic. The simulated vegetation distribution (1961-1990) agreed well with a composite map of actual arctic vegetation. In the future (2051-2080), a poleward advance of the forest-tundra boundary, an expansion of tall shrub tundra, and a dominance shift from deciduous to evergreen boreal conifer forest over northern Eurasia were simulated. Ecosystems continued to sink carbon for the next few decades, although the size of these sinks diminished by the late 21st century. Hot spots of increased CH4 emission were identified in the peatlands near Hudson Bay and western Siberia. In terms of their net impact on regional climate forcing, positive feedbacks associated with the negative effects of tree-line, shrub cover and forest phenology changes on snow-season albedo, as well as the larger sources of CH4, may potentially dominate over negative feedbacks due to increased carbon sequestration and increased latent heat flux.
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