Application of the HBV model for the future projections of water levels using dynamically downscaled global climate model data

The Hydrologiska Byråns Vattenbalansavdelning (HBV) model was used to project the future water levels of the Mackenzie River at selected stations. The Weather Research and Forecasting (WRF) model was utilized to dynamically downscale the Global Climate Model data. The calibrated and validated HBV model was run with the WRF downscaled CanESM2 data and with the PCIC data for the historical (1979–2005) period, and then compared with the observed flow data at the Fort Simpson station and the Arctic Red River station. The simulated streamflow showed a good correlation with the observed streamflow (R2 value was around 0.85). The HBV model was then forced with the bias-corrected WRF downscaled daily rainfall and temperature data driven by the CanESM2 RCP 4.5 and RCP 8.5 climate scenarios to simulate the future streamflow for the 2041–2070 period. Rating curves were used to convert streamflow to water levels. At the Fort Simpson station, mean flow was projected to decrease by about 5% under both RCP 4.5 and RCP 8.5 scenarios, whereas the peak flow was likely to reduce by about 12 and 9% for RCP 4.5 and RCP 8.5 scenarios, respectively, in the 2050s. The projected lower water levels could affect the navigability and the northern ferry operations of the Mackenzie River.

Towards more physically constrained freshwater injection via eddy permitting simulations of the last glacial cycle

<p>Freshwater, in the form of glacial runoff, is hypothesized to play a critical role in centennial to millennial scale climate variability, eg. the Younger Dryas and Dansgaard Oeschger events. Freshwater injection, or hosing, model experiments demonstrate that freshwater has the capability to generate abrupt climate transitions.  However, in an attempt to mitigate the inability of most models to resolve the smaller-scale features relevant to freshwater transport (such as boundary currents and mesoscale eddies), these hosing experiments commonly apply the entirety of the freshwater directly to the regions of deepwater formation (DWF). Our results indicate that this can inflate the freshwater signal in those regions by as much as four times. We propose a novel method of freshwater injection for such low-resolution models that spatially distributes the freshwater in accord with the results of eddy-permitting modelling. Furthermore, this “freshwater fingerprint” method not only impacts the timing of simulated climate transitions but also can allow us to evaluate how much we are overestimating the effects of freshwater when injected directly into sites of DWF.</p><p> </p><p>The freshwater fingerprints we develop are based on a suite of freshwater injection experiments performed using an eddy permitting Younger Dryas configuration of the MITGCM. Freshwater injection locations include the Mackenzie River, Gulf of St. Lawrence, Gulf of Mexico and a location off the coast of Norway, with flux amounts bounded by glacial reconstructions. These simulations indicate that freshwater from the Mackenzie River and Fennoscandia have the largest impact on salinity in most of the conventional sites of DWF (GIN and Labrador Seas, and in these simulations, predominantly the northern North Atlantic due to extensive sea ice), while freshwater from the Gulf of St. Lawrence is effective at freshening only the northern North Atlantic. The Gulf of Mexico has little impact on any DWF region we consider, mostly because the lower but continual flux in our simulations does not allow freshwater to penetrate northward past the Gulf Stream. The dilution of the freshwater signal as it is transported from the site of injection to the DWF zones leads to a reduction in the effective freshwater forcing, making hosing directly over DWF zones even with realistic freshwater amounts unrealistic. Thus, we construct freshwater fingerprints from these simulations by extracting the freshwater anomaly spatial pattern averaged over the last 5 simulation years, vertically integrating the field and normalizing it.</p><p><br>The freshwater fingerprint is then implemented in the COSMOS Earth Systems Model, which is run at resolutions typical for paleoclimate simulations (non-eddy permitting). Initial results show that freshwater from the Mackenzie River using our  fingerprint method leads to a more gradual cooling than if the meltwater is released directly over the hosing region (50-70N). We conclude that hosing over DWF zones, even with realistic freshwater amounts, produces an unrealistically large climate response. Additional results for the remaining injection locations and with the fingerprint implemented in a simpler climate model will be presented.</p>

The stock and age of pyrogenic carbon in boreal forest soils of the Mackenzie Basin, Northern Canada

<p>Wildfires occur regularly in the boreal forests of Northern Canada and an increasing frequency and intensity due to the global climate change is projected. A by-product of these forest fires is pyrogenic carbon (PyC) as a residue of incomplete combustion. The quantity and age of PyC in boreal forest soils, however, are largely unknown although boreal soils contribute to a large extent to the global soil organic carbon (SOC) stocks. The Mackenzie River is a major export pathway for PyC between terrestrial and marine environments, with exported PyC ages on geological timescales. This indicates that soil may play an important role as an intermediate pool prior to the PyC export. We sampled eleven forest soils (with nine replicates) in the Canadian Taiga Plains and Shield within the Mackenzie River basin. Our sample sites were located in regions with soils under continuous permafrost in the Inuvik region (northern sites) and under sporadic and discontinuous permafrost in the South Slave Lake regions (southern sites). All sites were unaffected by fire for at least four decades. We used the hydrogen pyrolysis (HyPy) method to separate the PyC<sub>HyPy</sub> from the non-fire-derived SOC in the upper 0-15 cm to determine PyC<sub>HyPy</sub> stocks and performed radiocarbon dating upon both bulk soil and isolated PyC<sub>HyPy</sub>. The total SOC stocks were lower in the soil from the southern sites with on average 26 ± 20 Mg ha<sup>-1</sup> (10-153 Mg ha<sup>-1</sup>) compared to 57 ± 29 Mg ha<sup>-1</sup> (16-188 Mg ha<sup>-1</sup>) in the northern sites. The radiocarbon dating revealed much older PyC<sub>HyPy</sub> compared to the bulk soil SOC radiocarbon age, supporting the persistent nature of PyC and stabilization in soils. The PyC<sub>HyPy </sub>found in the soil of the southern sites, however, was much younger with ages in the range of 495-3 275 radiocarbon years BP than in the northern sites with ages on the range of 2 083-10 407 radiocarbon years BP. The larger SOC stocks and higher ages of PyC<sub>HyPy</sub> in the soils of the northern sites indicate the importance of permafrost conditions for the whole carbon cycle of boreal forests soils.</p>

Importance of environmental flows in the Wimmera catchment, Southeast Australia

In this paper the environment, climate, vegetation, indigenous and European settlement history, stream flow patterns, water quality and water resources development in western Victoria, Australia are studied. The last part of the paper focuses on the MacKenzie River, a tributary of the Wimmera River located on the northern slopes of the Grampians Ranges in western Victoria, Australia. Water release along the MacKenzie River was regulated to improve water quality, stream condition and river health especially in the downstream reaches. The upstream section tends to receive water most days of the year due to releases to secure the requirements of water supply for the city of Horsham and its recreational and conservation values, which is diverted into Mt Zero Channel. Below this the middle and downstream sections receive a more intermittent supply. Annually, a total of 10,000 dam3 of water is released from Wartook Reservoir into the MacKenzie River. Of this volume, only about 4,000 dam3 was released explicitly for environmental purposes. The remaining 6,000 dam3 was released to meet consumptive demands and to transfer water to downstream reservoirs. The empirical data and models showed the lower reaches of the river to be in poor condition under low flows, but this condition improved under flows of 35 dam3 per day, as indicated. The results are presented to tailor discharge and duration of the river flows by amalgamation of consumptive and environmental flows to improve the condition of the stream, thereby supplementing the flows dedicated to environmental outcomes. Ultimately the findings can be used by management to configure consumptive flows that would enhance the ecological condition of the MacKenzie River.