Multi-temporal mapping of the Upper Rhone Valley (Valais, Switzerland): fluvial landscape changes at the end of the Little Ice Age (18th–19th centuries)

Since the end of the Little Ice Age (LIA), formerly glaciated areas have undergone considerable changes in their morphodynamics due to external forces and system-internal dynamics. Using multi-temporal high-resolution digital elevation models (DEMs) from different remote sensing techniques such as historical digital aerial images and light detection and ranging (LiDAR), and the resulting DEMs of difference (DoD), spatial erosion and accumulation patterns can be analyzed in proglacial areas over several decades. In this study, several morphological sediment budgets of different test sites on lateral moraines and different long-term periods were determined, covering a total period of 49 years. The test sites show high ongoing morphodynamics, and therefore low vegetation development. A decrease as well as an increase of the mean annual erosion volume could be demonstrated at the different test sites. All test sites show a slope–channel coupling and a decrease in the efficiency of sediment transport from slopes to channels. These developments are generally subject to conditions of increasing temperature, decreasing short-term precipitation patterns and increasing runoff from adjacent mountain streams. Finally, the study shows that sediment is still available on the investigated test sites and the paraglacial adjustment process is still in progress even after several decades of deglaciation (~133 years).

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Glacial reduction in the Gran Paradiso Massif (Western Italian Alps): multitemporal dynamic inventory since the Little Ice Age

10.5194/egusphere-egu2020-10734 ◽

2020 ◽

Author(s):

Simona Gennaro ◽

Maria Cristina Salvatore ◽

Linda Alderighi ◽

Riccardo Cerrato ◽

Carlo Baroni

Keyword(s):

Little Ice Age ◽

Quantitative Data ◽

Reduction Rate ◽

Temporal Analysis ◽

Ice Age ◽

European Alps ◽

Italian Alps ◽

Multi Temporal ◽

Gran Paradiso ◽

The Impact

Alpine glaciers are sensitive key markers of climate variations, as their geometry and shape are the results of adjustments in response to changes of their mass balance. Since the Little Ice Age the European Alps, as well as other mountain ranges, experienced a phase of generalized retreat, accentuated during the last decades. The availability of quantitative data on glaciers variations from major mountain regions represent relevant tools for better understanding the glacier behaviour in response to ongoing climatic changes. Here we present new data on Holocenic variations of glaciers hosted in the Gran Paradiso Massif, the first Italian National Park (Western Italian Alps).We built the multi-temporal digital inventory of the Gran Paradiso Massif glaciers covering a time period of over 150 years, considering distinct time steps spanning from the Little Ice Age (LIA) to 2015. The multi-temporal dataset was built including glaciers outlines (derived from high resolution orthophotos and historical maps) and the data related to frontal variations (coming from annual glaciological surveys conducted by the Italian Glaciological Committee). Database was managed in GIS environment and populated following the guidelines suggested by the WGMS. Multi-temporal analysis supplied new quantitative data on the strong glacial decline occurred since the LIA and dramatically accelerated since the 90s.During the LIA the Gran Paradiso Massif hosted more than 120 glaciers extended for about 112 km2 reduced to 73 units in 2015 covering only about 32 km2.Our data underline a loss of about 50 &#177; 4 m w.e. and ELA variations of about 166/130 &#177; 5/4 m (considering AAR/AABR methods, respectively) from the maximum LIA position and 2006. The strong contraction and fragmentation of the studied glaciers is underlined by area loss of over 71% (with a reduction rate of -0.36% y-1) from the LIA to 2015, as well as by the increase in the number of glacial bodies smaller than 0.1 km2, and by the increase in the number of extinct glaciers (33 in 2015 respect to 1957). Furthermore, during the last decades, new data obtained show a dramatic acceleration in the contraction rates of the glacial bodies, which can lead to impressive landscape changes and to a relevant increase of geomorphological hazard.The multitemporal data show a very detailed evolution of Gran Paradiso glaciers also considering ice- mass loss and can contribute to modelling glaciers response to climate changes in a sensitive area of the Italian Alps, considering its location at the border of a &#8220;dry zone&#8221;. Improving the knowledge on the glacial resource could contribute in better understanding the impact of warming climate on mountain hydrology, as well as to increase the awareness of the population and authorities to be resilient in a near future with strong reduction of meltwater runoff.

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Greenhouses, hot water bottles, cycles and the future of New Zealand climate

Proceedings of the New Zealand Grassland Association ◽

10.33584/jnzg.2009.71.2772 ◽

2009 ◽

pp. 61-67

Author(s):

W.P. De Lange

Keyword(s):

New Zealand ◽

Thermal Energy ◽

Infrared Radiation ◽

Little Ice Age ◽

Hot Water ◽

Ice Age ◽

The Sun ◽

Weather Patterns ◽

Time Periods ◽

Almost All

The Greenhouse Effect acts to slow the escape of infrared radiation to space, and hence warms the atmosphere. The oceans derive almost all of their thermal energy from the sun, and none from infrared radiation in the atmosphere. The thermal energy stored by the oceans is transported globally and released after a range of different time periods. The release of thermal energy from the oceans modifies the behaviour of atmospheric circulation, and hence varies climate. Based on ocean behaviour, New Zealand can expect weather patterns similar to those from 1890-1922 and another Little Ice Age may develop this century.

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