Increased attention directed at the permafrost region has been prompted by resource development and climate change. This review surveys advances in permafrost hydrology since 2000. Data shortage and data quality remain serious concerns. Yet, there has been much progress in understanding fundamental hydrologic processes operating in a wide range of environments, from steep mountainous catchments, to the Precambrian Shield with moderate relief, to the low-gradient terrain of plains, plateaus and wetlands. Much of the recent research has focused on surface water, although springs and groundwater contribution to streamflow have also been studied. A compendium of water-balance research from 39 high-latitude catchments reveals the strengths and limitations of the available results, most of which are restricted to only a few years of study at the small watershed scale. The response of streamflow to climate receives continued if not increasing attention, from the occurrence of extreme hydrologic events to the changing regimes of river flow at a regional scale. The effect of climate change and the role of permafrost on the changing discharge of large boreal rivers are major topics for further investigation. Extended field and modelling research on physical processes will improve knowledge of permafrost hydrology and enhance its relevance to societal needs. Copyright # 2008 John Wiley & Sons, Ltd.

Progress in permafrost hydrology in the new millennium

The areal extent of permafrost in China has been reduced by about 18.6 % during the last 30 years. Due to the combined influences of climate warming and human activities, permafrost has been degrading extensively, with marked spatiotemporal variability. Distribution and thermal regimes of permafrost and seasonal freeze-thaw processes are closely related to groundwater dynamics. Permafrost degradation and changes in frost action have extensively affected cold-regions hydrogeology. Progress on some research programs on groundwater and permafrost in two regions of China are summarized. On the Qinghai-Tibet Plateau and in mountainous northwest China, permafrost is particularly sensitive to climate change, and the permafrost hydrogeologic environment is vulnerable due to the arid climate, lower soil-moisture content, and sparse vegetative coverage, although anthropogenic activities have limited impact. In northeast China, permafrost is thermally more stable due to the moist climate and more organic soils, but the presence or preservation of permafrost is largely dependent on favorable surface coverage. Extensive and increasing human activities in some regions have considerably accelerated the degradation of permafrost, further complicating groundwater dynamics. In summary, permafrost degradation has markedly changed the cold-regions hydrogeology in China, and has led to a series of hydrological, ecological, and environmental problems of wide concern.

Permafrost and groundwater on the Qinghai-Tibet Plateau and in northeast China

Hydrological factors in the interpretation of stable isotopic proxy data present and past: a European perspective

[1] Groundwater discharge to rivers has increased in recent decades across the circumpolar region and has been attributed to thawing permafrost in arctic and subarctic watersheds. Permafrost-driven changes in groundwater discharge will alter the flux of dissolved organic carbon (DOC) in rivers, yet little is known about the chemical composition and reactivity of dissolved organic matter (DOM) of groundwater in permafrost settings. Here, we characterize DOM composition of winter flow in 60 rivers and streams of the Yukon River basin to evaluate the biogeochemical consequences of enhanced groundwater discharge associated with permafrost thaw. DOC concentration of winter flow averaged 3.9 ± 0.5 mg C L−1, yet was highly variable across basins (ranging from 20 mg C L−1). In comparison to the summer-autumn period, DOM composition of winter flow had lower aromaticity (as indicated by specific ultraviolet absorbance at 254 nm, or SUVA254), lower hydrophobic acid content, and a higher proportion of hydrophilic compounds (HPI). Fluorescence spectroscopy and parallel factor analysis indicated enrichment of protein-like fluorophores in some, but not all, winter flow samples. The ratio of DOC to dissolved organic nitrogen, an indicator of DOM biodegradability, was positively correlated with SUVA254and negatively correlated with the percentage of protein-like compounds. Using a simple two-pool mixing model, we evaluate possible changes in DOM during the summer-autumn period across a range of conditions reflecting possible increases in groundwater discharge. Across three watersheds, we consistently observed decreases in DOC concentration and SUVA254 and increases in HPI with increasing groundwater discharge. Spatial patterns in DOM composition of winter flow appear to reflect differences in the relative contributions of groundwater from suprapermafrost and subpermafrost aquifers across watersheds. Our findings call for more explicit consideration of DOC loss and stabilization pathways associated with changing subsurface hydrology in watersheds underlain by thawing permafrost.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2012GB004341

Dissolved organic matter composition of winter flow in the Yukon River basin: Implications of permafrost thaw and increased groundwater discharge

. The cryosphere reacts sensitively to climate change, as evidenced by the widespread retreat of mountain glaciers. Subsurface ice contained in permafrost is similarly affected by climate change, causing persistent impacts on natural and human systems. In contrast to glaciers, permafrost is not observable spatially and therefore its presence and possible changes are frequently overlooked. Correspondingly, little is known about permafrost in the mountains of the Hindu Kush Himalaya (HKH) region, despite permafrost area exceeding that of glaciers in nearly all countries. Based on evidence and insight gained mostly in other permafrost areas globally, this review provides a synopsis on what is known or can be inferred about permafrost in the mountains of the HKH region. Given the extreme nature of the environment concerned, it is to be expected that the diversity of conditions and phenomena encountered in permafrost exceed what has previously been described and investigated. We further argue that climate change in concert with increasing development will bring about diverse permafrost-related impacts on vegetation, water quality, geohazards, and livelihoods. To better anticipate and mitigate these effects, a deepened understanding of high-elevation permafrost in subtropical latitudes as well as the pathways interconnecting environmental changes and human livelihoods are needed.

/pdf/review-article-inferring-permafrost-and-permafrost-thaw-in-5e7qdnplfp.pdf

Review article: Inferring permafrost and permafrost thaw in the mountains of the Hindu Kush Himalaya region

Groundwaters, surface runoff and river discharge have been studied at the Fish Hole area of the Big Fish River catchment, near Aklavik, N.W.T, to quantify the seasonal variations in groundwater contributions to baseflow in a permafrost basin. Geochemical and isotope methods are used to distinguish three principal water types: (1) subpermafrost Na-Cl thermal waters (16?C) discharging from bedrock along the river, (2) shallow, Ca-SO4 groundwaters, and (3) low-salinity, Ca-HCO3, suprapermafrost drainage. Cl and SO4 concentrations in river water show that baseflow is largely derived from groundwater sources (Na-Cl and CaS04 components), with less than 30% contributed from surface water runoff in any season. Thermal groundwaters discharge year-round at a calculated 1.6 m3 s-~. The shallow, Ca-SO4 groundwater is the dominant component of baseflow in summer but is absent in winter baseflow. Discharge analysis based on a single flow measurement (25.5 m3 s-1 in June, 1997) and Cl-dilution allows calculation of total river discharge. This is shown to vary from a low of 2.2 m3 s-' in the winter, to 1050 m3 s-~ during early spring melt.

Lois Harwood

Papers

Groundwater Contributions to Discharge in a Permafrost Setting, Big Fish River, N.W.T., Canada