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The glacier sedimentary system
Published in Richard J. Chorley, Stanley A. Schumm, David E. Sugden, Geomorphology, 2019
Richard J. Chorley, Stanley A. Schumm, David E. Sugden
Glacier meltwater is derived from melting on the surface and within a glacier. Surface sources are more important than internal sources by an order of magnitude and are usually highly seasonal in character reflecting the effect of summer ablation on the glacier surface. In effect the bulk of the annual precipitation of a glacier may be discharged in only a few summer months. Meltwater of internal and basal origin is small in comparison but may be produced throughout the- year. Internal sources involve ice melting in conduits and water produced by internal deformation of ice at the pressure melting point. Basal water is derived from geothermal heat melting the base of ice at the pressure melting point. On average this heat is enough to melt a layer of ice about 6 mm in thickness. Although not strictly meltwater, a varying proportion of the water flowing through a glacier in summer may be derived from rainfall or groundwater flow in a glacier catchment.
Food
Published in John C. Ayers, Sustainability, 2017
Although a higher atmospheric concentration of carbon dioxide may aid photosynthesis and crop growth, this effect is more than offset by the increased temperatures and decreased soil moisture it will cause5 (Long et al. 2006). For example, crop yields decrease sharply when temperatures exceed ~30°C (86°F) (Schlenker and Roberts 2009). Furthermore, extreme weather events such as the drought in Australia and the 2010 heat wave in Russia caused many of the crop failures of the past decade, and scientists believe at least some of those events were caused or worsened by climate change,6 and that extreme weather events will increase in frequency as climate change intensifies. In the longer term, climate change will cause profound changes in water availability in many geographic regions. For example, regional warming will cause alpine glaciers to decrease in volume and to melt earlier in the year, reducing the amount of melt-water supplied to lowlands in the spring and summer when it is most needed for agriculture (Barnett, Adam, and Lettenmaier 2005). This is already occurring in the U.S. west where farmland fed by glacial meltwaters from the Rocky Mountains is drying up, hydropower production is falling, and the intensity of regional droughts and forest fires is increasing (Struzik 2014).
Climate Change and Drought: Building Resilience for an Unpredictable Future
Published in Saeid Eslamian, Faezeh Eslamian, Handbook of Drought and Water Scarcity, 2017
Hamideh Maleksaeidi, Marzieh Keshavarz, Ezatollah Karami, Saeid Eslamian
The analysis of model-simulated soil moisture [107,126], drought indices [20,27], and precipitation minus evaporation [100] suggests increased risk of drought in the twenty-first century. For example, Burke et al. [21] simulated changes in the PDSI over the twenty-first century. They projected an overall drying trend, accelerating through the twenty-first century, with particularly strong drying over Amazonia, the United States, northern Africa, southern Europe, and eastern Asia. According to these projections, the percentage of area under “severe” drought will increase from around 10% at the beginning of the twenty-first century to around 40% at the end. The frequency of “severe” drought events will double by the end of the century and their mean duration will increase by a factor of around five [21]. Also, IPCC [60] predicted that in 2050, the annual average river flow would increase by 10%–40% at high latitudes and decrease by 10%–30% over some dry regions at mid-latitudes and semiarid low latitudes, which are already water-stressed areas. Few studies have projected explicitly the hydrological drought incidence. Van Lanen et al. [121] revealed that climate change is projected to worsen high temperatures and drought due to reducing streamflow during summer in downstream regions that are supplied by meltwater from major mountain ranges in southern Europe. Globally, Arnell [8] estimated that by the 2050s, about 670–1500 million people living in water-stressed watersheds would experience a significant reduction in water availability due to climate change. Most of these people would be around the Mediterranean and in the Middle East, central Asia and southern Africa.
Genesis of hummocks found in tunnel valleys: an example from Hörda, southern Sweden
Published in GFF, 2018
Gustaf Peterson, Mark D. Johnson, Sandra Dahlgren, Tore Påsse, Helena Alexanderson
Meltwater production from glaciers is expected to increase as a result of a warming climate (Tedesco et al. 2012). Moreover, sudden drainage of subglacial and supraglacial lakes at the Greenland and Antarctic ice sheets of up to billions of cubic meters of water creates a highly dynamic glacial hydrological system (Stearns et al. 2008; Dow et al. 2015; Palmer et al. 2015; Willis et al. 2015). The evolution of the hydrologic systems in former ice sheets during periods with increased amounts of meltwater is still a field about which little is known (Greenwood et al. 2016). However, geomorphologic mapping and sedimentological studies of imprints and deposits from the subglacial hydrological system of formerly glaciated regions have the capacity to deepen our understanding of ice-sheet response to increased meltwater production.
The United Nations World Water Development Report 2022 on groundwater, a synthesis
Published in LHB, 2022
Across continental northern latitudes, as well as in mountainous and polar regions, global warming alters meltwater flow regimes from ice and snow, impacting groundwater recharge. In temperate regions, warming results in less snow accumulation and earlier snowmelt, as well as more winter precipitation falling as rain and an increased frequency of rain-on-snow events. The aggregate impact of these effects is a reduced seasonal duration and magnitude of recharge, which lowers water storage in catchments and amplifies severe summer low flows, so that streamflow becomes inadequate to meet domestic and agricultural water requirements and to maintain ecological functions (105).