Producing hydrologic scenarios from raw climate model outputs using an asynchronous modelling framework

Statistical post-processing of climate model outputs is a common hydroclimatic modelling practice aiming to produce climate scenarios that better fit in-situ observations and to produce reliable stream flows forcing calibrated hydrologic models. Such practice is however criticized for disrupting the physical consistency between simulated climate variables and affecting the trends in climate change signals imbedded within raw climate simulations. It also requires abundant good-quality meteorological observations, which are not available for many regions in the world. A simplified hydroclimatic modelling workflow is proposed to quantify the impact of climate change on water discharge without resorting to meteorological observations, nor for statistical post-processing of climate model outputs, nor for calibrating hydrologic models. By combining asynchronous hydroclimatic modelling, an alternative framework designed to construct hydrologic scenarios without resorting to meteorological observations, and quantile perturbation applied to streamflow observations, the proposed workflow produces sound and plausible hydrologic scenarios considering: (1) they preserve trends and physical consistency between simulated climate variables, (2) are implemented from a modelling cascades despite observation scarcity, and (3) support the participation of end-users in producing and interpreting climate change impacts on water resources. The proposed modelling workflow is implemented over four subcatchments of the Chaudière River, Canada, using 9 North American CORDEX simulations and a pool of lumped conceptual hydrologic models. Forced with raw climate model outputs, hydrologic models are calibrated over the reference period according to a calibration metric designed to function with temporally uncorrelated observed and simulated streamflow values. Perturbation factors are defined by relating each simulated streamflow quantiles over both reference and future periods. Hydrologic scenarios are finally produced by applying perturbation factors to available streamflow observations.

Effect of Salinity on Evaporation from Water Surface in Bench-Scale Testing

Freshwater and hypersaline lakes in arid and semi-arid environments are crucial from agricultural, industrial, and ecological perspectives. The purpose of this paper was to investigate the effect of salinity on evaporation from water surfaces. The main achievement of this research is the successful capture of simulated climate–surface interactions prevalent in the Canadian Prairies using a custom-built bench-scale atmospheric simulator. Test results indicated that the evaporative flux has a large variation during spring (water/brine: 1452/764 10−4 g·s−1·m−2 and 613/230 × 10−4 g·s−1·m−2 night) and summer (1856/1187 × 10−4 g·s−1·m−2 day and 1059/394 × 10−4g·s−1·m−2 night), and small variation in the fall (1591/915 × 10−4 g·s−1·m−2 and 1790/1048 × 10−4 g·s−1·m−2 night). The primary theoretical contribution of this research is that the evaporation rate from distilled water is twice that of saturated brine. The measured data for water correlated well with mathematical estimates; data scatter was evenly distributed and within one standard deviation of the equality line, whereas the brine data mostly plotted above the equality line. The newly developed 2:1 water–brine correlation for evaporation was found to follow the combination equations with the Monteith model best matching the measurements.

Responses of Terrestrial Mosses to Simulated Climate Change in a Secondary Evergreen Broad-leaved Forest in Southern China

Tropical regions are biodiversity hotspots and are well suited to explore the potential influence of global climate change on forest ecosystems. Bryophytes have essential ecological functions in tropical forest ecosystems. Knowledge of the potential impact of global warming and possible changes in water availability patterns on terrestrial bryophytes is limited. We transplanted eight moss species from two elevations (900 and 500 m) to warmer and drier elevations (500 and 100 m) during a half-year observation period on Tai Mo Shan, southern China. The simulated climate change resulted in a marked decrease in growth and a negative effect on the health of the transplanted species. Few moss species survived six months after transplanting to the warmer and drier lowlands, and their health status deteriorated severely. Three moss species, Sematophyllum subhumile, Pseudotaxiphyllum pohliaecarpum, and Brachythecium buchananii, were highly susceptible to changes in temperature and moisture and might be used as suitable bioindicators. As the tropics are expected to become hotter and drier, terrestrial mosses might be negatively affected or even be at risk of extinction. The cascading negative effects on the forest ecosystem might be induced by the dying back or even disappearance of terrestrial moss species. Thus, conservation of bryophyte communities is important to sustain and improve the stability and resilience of tropical forest ecosystems to climate change.

How does simulated climate change affect the susceptibility of SOM to priming by LMWOS in the Subarctic?

<p>Soil organic matter (SOM) stabilization plays an important role in the long-term storage of carbon (C). However, many ecosystems are undergoing climate change, which will change the soil C balance via altered plant communities and productivity that change C inputs, and altered C losses via changes in SOM decomposition. The ongoing change of aboveground plant communities in the Subarctic (“greening”) will increase rhizosphere inputs containing low molecular weight organic substances (LMWOS), which will likely affect C-starved microbial decomposers and their subsequent contribution to SOM mineralization (priming effect).In the present study, we simulated the effects of climate change with N fertilization (simulating warming enhanced nutrient cycling) and litter additions (simulating arctic greening) in Abisko, Sweden. The 6 sampled field-treatments included a full factorial combination of 3-years of chronic N addition and litter additions, as well as, a single year of extreme climate change (3x N fertilizer or litter additions in one growth season). We found that N treatments changed plant community composition and productivityand that the associated shift in belowground LMWOS induced shifts in the soil microbial community. In the chronic N fertilization treatments, plant productivity, and therefore belowground LMWOS input, increased. This coincided with a tendency for more bacterial dominated decomposition (lower fungi/bacterial growth ratio). However, N treatments had no effect on soil C mineralization, but increased gross N mineralization.</p><p>These responses in belowground communities and processes driven by rhizosphere input prompted the next question: how does simulated climate change affect the susceptibility of SOM to priming by LMWOS? To assess this question and determine the microbial mechanisms underpinning priming of SOM mineralization, we added a factorial set of additions including <sup>13</sup>C-glucose with and without mineral N, and <sup>13</sup>C-alanine semi-continuously (every 48 hours) to simulate the effect of rhizosphere LMWOS on SOM mineralization and microbial activity. We incubated these samples for 2 weeks and assessed the priming of soil C and gross N mineralization, bacterial and fungal growth rates, PLFAs, enzyme activities, and microbial C use efficiency (CUE). We found that alanine addition primed soil C mineralization by 34%, which was higher than soil C priming induced by glucose and glucose with N. Furthermore, glucose primed fungal growth, whereas the alanine primed bacterial growth, but microbial PLFAs did not respond to either treatment. The C enzyme acquisition activity was higher than N enzyme acquisition activity in all the treatments, while P enzyme acquisition activity was higher than C for all the treatments. Surprisingly, this suggested a chronic microbial limitation by P, which was unaffected by field and lab treatments. LMWOS additions generally reduced microbial CUE. Responses of microbial mineralization of N from SOM to LMWOS suggested a directed microbial effort towards targeting resources that limited bacterial or fungal growth, suggesting that microbial SOM-use shifted to N-rich components (selective microbial “N-mining”), in contrast with enzyme results. Surprisingly, alanine primed the highest N mineralization compared other additions indicating that there was strong N-mining even if N was sufficient.</p>

The last deglaciation simulated with a coupled atmosphere/ocean/ice sheet/solid earth model

<p>It is challenging to model the last deglaciation, as it is characterized by abrupt millennial scale climate events, such as ice-sheet surges, that are superimposed on long-term climate changes, such as a global warming and the decay of a substantial part of the glacial ice sheets. Within PMIP, several groups have simulated the last deglaciation with CMIP-type models prescribing ice sheets from reconstructions. Whereas this type of simulations accounts for the effects of ice-sheet changes including meltwater release on climate, the prescribed ice sheet evolution is typically not consistent with the simulated climate evolution. Here we present a set of deglacial simulations that include fully interactive ice sheets that respond to changes in the climate. The setup also allows for feedbacks between ice sheets and climate and , hence, allows for a more realistic representation of the mechanisms of the last deglaciation, as the simulated climate and ice sheet changes are fully consistent..</p><p>The model consists of the coarse resolution set-up of MPI-ESM coupled to the ice sheet model mPISM (Northern Hemisphere and Antarctica) and the solid earth model VILMA. The model includes interactive icebergs and an automated calculation of the land-sea mask and river routing directions. A set of synchronously coupled simulations were started from an asynchronously coupled spin-up at 26ky and integrated throughout the deglaciation into the Holocene. The only prescribed external forcing are atmospheric concentrations of greenhouse gases and earth orbital parameters. One goal of this ensemble was to find the optimal combination of model parameters for the simulation of the deglaciation.</p><p>The model simulates the decay of the ice sheets, the rise of sea level, the flooding of shelf seas and the opening of passages. A large fraction of the ice sheet retreat is due to dynamical events (e.g. the final decay of the ice sheets on Barents Shelf or the Hudson Bay). Superimposed on the relatively slow glacial/interglacial transition are abrupt climate changes, triggered for example by recurrent ice sheet surges. These surges correspond to Heinrich Events tand result in a weakening of the AMOC. Three source regions for ice sheet surges occur during these simulations: from the Laurentide ice sheet through Hudson Strait, from the Laurentide ice sheet northward directly to the Arctic ocean, and from the Fennoscandian ice sheet into the Norwegian Sea. The characteristic climate response shows a large dependence on the surge location.</p><p>The simulated changes in strength of the AMOC are except for millennial-scale reduction events only moderate. However, during glacial periods, brine release is the central process for deep water formation in both hemispheres, in contrast to the Holocene. dDuring the deglaciation the ventilation of the deep ocean is strongly reduced, leading to a strong increase of the simulated deep water ages. This effect lasts longest in the deep North Pacific and extends in some simulations into the Holocene.</p>