scholarly journals On the effect of short-term climate variability on mountain glaciers: insights from a case study

2013 ◽  
Vol 59 (217) ◽  
pp. 992-1006 ◽  
Author(s):  
Daniel Farinotti
Keyword(s):  
Climatic Variability ◽  
Swiss Alps ◽  
Ice Dynamics ◽  
Mountain Glaciers ◽  
Temperature And Precipitation ◽  
Glacier Ice ◽  
Long Term Trends ◽  
Model Set ◽  
Set Up

AbstractStudies addressing the response of glaciers to climate change have so far analyzed the effect of long-term trends in a particular set of meteorological variables only, implicitly assuming an unaltered climatic variability. Here a framework for distinguishing between year-to-year, month-to-month and day-to-day variability is proposed. Synthetically generated temperature and precipitation time series following the same long-term trend but with altered variability are then used to force an ice-dynamics model set up for Rhonegletscher, Swiss Alps. In the case of temperature, variations in the day-to-day variability are shown to have a larger effect than changes at the yearly scale, while in the case of precipitation, variability changes are assessed as having negligible impact. A first set of scenarios is used to show that compared to reference, doubling the temperature variability can reduce glacier ice volume by up to 64% within half a decade. A second set derived from the results of the European ENSEMBLES project, however, shows that such changes are expected to remain below 8% even for extreme scenarios. Although the latter results relativize the importance of the effect in the near future, the analyses indicate that at least caution is required when assuming ‘unchanged variability’.

scholarly journals Strengths and challenges for transient Mid- to Late Holocene simulations with dynamical vegetation

2019 ◽  
Vol 15 (3) ◽  
pp. 997-1024 ◽  
Author(s):  
Pascale Braconnot ◽  
Dan Zhu ◽  
Olivier Marti ◽  
Jérôme Servonnat
Keyword(s):  
Northern Hemisphere ◽  
Forest Cover ◽  
Heat Content ◽  
Forest Composition ◽  
Model Quality ◽  
Temperature And Precipitation ◽  
Transient Simulations ◽  
Long Term Trends ◽  
Set Up

Abstract. We present the first simulation of the last 6000 years with a version of the IPSL Earth system model that includes interactive dynamical vegetation and carbon cycle. It is discussed in the light of a set of Mid-Holocene and preindustrial simulations performed to set up the model version and to initialize the dynamical vegetation. These sensitivity experiments remind us that model quality or realism is not only a function of model parameterizations and tunings but also of experimental setup. The transient simulations shows that the long-term trends in temperature and precipitation have a similar shape to the insolation forcing, except at the Equator, at high latitudes, and south of 40∘ S. In these regions cloud cover, sea ice, snow, or ocean heat content feedbacks lead to smaller or opposite temperature responses. The long-term trend in tree line in the Northern Hemisphere is reproduced and starts earlier than the southward shift in vegetation over the Sahel. Despite little change in forest cover over Eurasia, a long-term change in forest composition is simulated, including large centennial variability. The rapid increase in atmospheric CO2 in the last centuries of the simulation enhances tree growth and counteracts the long-term trends induced by Holocene insolation in the Northern Hemisphere and amplifies it in the Southern Hemisphere. We also highlight some limits in the evaluation of such a simulation resulting from model climate–vegetation biases, the difficulty of fully assessing the result for preindustrial or modern conditions that are affected by land use, and the possibility of multi-vegetation states under modern conditions.

scholarly journals Neural Networks Applied to Estimating Subglacial Topography and Glacier Volume

2009 ◽  
Vol 22 (8) ◽  
pp. 2146-2160 ◽  
Author(s):  
Garry K. C. Clarke ◽  
Etienne Berthier ◽  
Christian G. Schoof ◽  
Alexander H. Jarosch
Keyword(s):  
Neural Network ◽  
Regional Scale ◽  
Ice Thickness ◽  
Ice Dynamics ◽  
Ice Caps ◽  
Mountain Glaciers ◽  
The Neural Network ◽  
Glacier Ice ◽  
Subglacial Topography ◽  
Artificial Neural Network Ann

Abstract To predict the rate and consequences of shrinkage of the earth’s mountain glaciers and ice caps, it is necessary to have improved regional-scale models of mountain glaciation and better knowledge of the subglacial topography upon which these models must operate. The problem of estimating glacier ice thickness is addressed by developing an artificial neural network (ANN) approach that uses calculations performed on a digital elevation model (DEM) and on a mask of the present-day ice cover. Because suitable data from real glaciers are lacking, the ANN is trained by substituting the known topography of ice-denuded regions adjacent to the ice-covered regions of interest, and this known topography is hidden by imagining it to be ice-covered. For this training it is assumed that the topography is flooded to various levels by horizontal lake-like glaciers. The validity of this assumption and the estimation skill of the trained ANN is tested by predicting ice thickness for four 50 km × 50 km regions that are currently ice free but that have been partially glaciated using a numerical ice dynamics model. In this manner, predictions of ice thickness based on the neural network can be compared to the modeled ice thickness and the performance of the neural network can be evaluated and improved. From the results, thus far, it is found that ANN depth estimates can yield plausible subglacial topography with a representative rms elevation error of ±70 m and remarkably good estimates of ice volume.

Long-Term Operating Results: Ash Monofill

2003 ◽  
Author(s):  
Richard W. Goodwin
Keyword(s):  
Heavy Metal ◽  
Residue Management ◽  
Water Addition ◽  
Beneficial Reuse ◽  
Field Compaction ◽  
Long Term Trends ◽  
Sound Engineering ◽  
Set Up ◽  
Management Recommendations

An ash monofill was studied from 1997 to 2001. Monitoring results of the lined landfill showed viability of liner since groundwater standards were not exceeded. Raw leachate of RCRA heavy metal leachate results show Chromium reaching groundwater standards while Lead, Cadmium and Zinc slightly exceed these standards. An upset incident of premature set-up of lime-laden ash caused a back-up and overflow condition in 1994. Adding water of solubilization and field compaction achieves optimal geo-technical properties and reduces heavy metal leachate. This water addition would have also reduced fugitive dust concerns. These principles of sound engineering management of MWC residues were well-known and widely publicized. If the landfill operator had applied these principles the upset incident could have been avoided. Long-term trends of RCRA heavy metal leachate results show compliance with groundwater standards, although Lead, Cadmium and Zinc exceed these standards. Application of sound engineering placement practice would have reduced these long-term trends. USA Regulatory officials should consider incorporating these principles into residue management recommendations, following Environment Canada’s example. Recognition and implementation of these principles would confirm that incinerator ash can be properly managed — to alleviate concerns — justifying their beneficial reuse.

scholarly journals Strength and limits of transient mid to late Holocene simulations with dynamical vegetation

2018 ◽  
Author(s):  
Pascale Braconnot ◽  
Dan Zhu ◽  
Olivier Marti ◽  
Jérôme Servonnat
Keyword(s):  
Northern Hemisphere ◽  
Internal Variability ◽  
Forest Composition ◽  
Model Quality ◽  
Complete Evaluation ◽  
Long Term Trends ◽  
Set Up ◽  
The Tropics ◽  
Scientific Questions

Abstract. We discuss here the first 6000 years long Holocene simulations with fully interactive vegetation and carbon cycle with the IPSL Earth system model. It reproduces the long term trends in tree line in northern hemisphere and the southward shift of Afro-Asian monsoon precipitation in the tropics in response to orbital forcing. The simulation is discussed at the light of a set of mid Holocene and pre industrial simulations performed to set up the model version and to initialize the dynamical vegetation. These sensitivity experiments remind us that model quality or realism is not only a function of model parameterizations and tuning, but also of experimental set up. They also question the possibility for bi-stable vegetation states under modern conditions. Despite these limitations the results show different timing of vegetation changes through space and time, mainly due to the pace of the insolation forcing and to internal variability. Forest in Eurasia exhibits changes in forest composition with time as well as large centennial variability. The rapid increase of atmospheric CO2 in the last centuries of the simulation contributes to enhance tree growth and counteracts the long term trends induced by Holocene insolation in the northern hemisphere. A complete evaluation of the results would require being able to properly account for systematic model biases and, more important, a careful choice of the reference period depending on the scientific questions.

The relevance of the past unsustainable increase of glacier runoff for large-scale basins in different climatological settings 

2021 ◽  
Author(s):  
Melissa Mengert ◽  
Ben Marzeion
Keyword(s):  
Water Availability ◽  
Large Scale ◽  
Global Climate ◽  
Drainage System ◽  
Mass Change ◽  
Mountain Glaciers ◽  
Temperature And Precipitation ◽  
Long Term Storage ◽  
Seasonal Runoff

<p>Depending on the seasonality of temperature and precipitation, mountain glaciers seasonally store and release large amounts of freshwater. Therefore, glaciers have a strong influence on water availability in many regions of the world. In an ongoing global climate change, glaciers have an additional impact on water availability, as the net amount of stored ice changes in an unsustainable way. This results in glaciers not only altering the seasonal runoff, but also adding a net input into the drainage system.<br>To better understand the interplay between seasonal and long-term storage changes, we suggest to split the monthly seasonal mass balance into a sustainable fraction, which is derived by balancing solid precipitation by ablation proportional to positive temperatures, and an unsustainable fraction, which causes long-term glacier mass change.</p><p>Similarly, we consider the effect of glacier area changes, allowing us to separate seasonal runoff into components attributable to (unsustainable) area change, (unsustainable) mass change, or the (sustainable) seasonal runoff from the glacier.</p><p>By applying the concept to a reconstruction of global glacier change, we illustrate how the glacier input into river basins in different climatological settings has been affected by the glacier mass loss during the 20th century. </p>

Preliminary investigation of long-term changes in the stratospheric N2O abundances as a proxy for the Brewer-Dobson Circulation in a climate model, dynamical and chemical reanalyses and observations.

2021 ◽  
Author(s):  
Daniele Minganti ◽  
Simon Chabrillat ◽  
Quentin Errera ◽  
Maxime Prignon ◽  
Emmanuel Mahieu
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Seasonal Cycle ◽  
Climate Model ◽  
Swiss Alps ◽  
High Latitudes ◽  
Hemispheric Differences ◽  
Early Results ◽  
Long Term Trends

<p>The Brewer-Dobson Circulation (BDC) is a wintertime stratospheric circulation characterized by upwelling of tropospheric air in the tropics, poleward flow in the stratosphere, and downwelling at mid and high latitudes, with important implications for chemical tracer distributions, stratospheric heat and momentum budgets, and mass exchange with the troposphere. <br>Nitrous oxide (N2O) is continuously emitted in the troposphere, where has no sinks, and transported into the stratosphere, where is destroyed by photodissociaiton. The lifetime of N2O is approximately 100 years, which makes it an excellent long-lived tracer for transport studies in the stratosphere. <br>In this study, we investigate the long-term N2O changes in the stratosphere using a number a different datasets. We analyze the simulation from the state-of-the-art Chemistry-Climate Model WACCM (period: 1990-2014), together with the BASCOE Chemistry-Transport Model driven by five dynamical reanalyses (ERA5, ERA-Interim, JRA-55, MERRA, MERRA-2, period: 1996-2014), and the chemical reanalysis of Aura Microwave Limb Sounder version 3 (BRAM3, period: 2004-2013). We will also compare those gridded data to ground-based observations from Fourier transform infrared spectrometer at the Jungfraujoch station in the Swiss Alps. <br>The long-term trends of the N2O concentration are investigated using the Dynamic Linear Model (DLM). The DLM is a regression model based on the Bayesian inference, which allow fitting atmospheric data with four main components: a linear trend, a seasonal cycle, a number of proxies (solar cycle, ENSO, QBO ?) and an autoregressive process. DLM has the advantage that the trend and the seasonal and regression coefficients depend on time; DLM can therefore detect changes in the recovered trend, and modulations of the amplitude of the regressors with time. <br>Early results show that the datasets exhibit hemispheric differences in the long-term N2O changes in the lower stratosphere. In the Southern Hemisphere, the DLM fit of the N2O concentrations increases across the datasets, but the resulting trend is statistically significant only in limited regions of the stratosphere. In the Northern Hemisphere, the N2O fit does not change significantly in the considered period, resulting in a near-zero trend. These hemispheric differences are in line with previous studies of transport that identify different long-term trends of tracers and mean age of air between the hemispheres. <br>The fit through the DLM allows the amplitude of the seasonal cycle component to vary in time. Preliminary results indicate that the time variations depend on the hemisphere in the extra-tropical regions. In the Southern Hemisphere, the datasets generally show a constant amplitude of the seasonal cycle throughout the considered periods, with the largest values in the high latitudes in response to the polar vortex. In the Northern Hemisphere, the inter-annual variations of the seasonal cycle amplitude are stronger, with BRAM3 showing the largest modulations. In addition, larger differences arise in the amplitude of the seasonal component. WACCM simulates large amplitudes of the seasonal cycle, while the reanalyses show smaller values. <br>A more detailed analysis of the results will include ground-based observations, and the extension of the CTM runs to a longer period that matches the length of the WACCM run.</p>

Analysis the Vegetation and Soil Moisture in Beijing-Tianjin Area to Prevent Desertification by Long-Term Satellite Remote Sensing

2013 ◽  
Vol 385-386 ◽  
pp. 388-391
Author(s):  
Jun Li ◽  
Feng Zhi Dai ◽  
Yuan Li ◽  
Chun Yu Yu ◽  
Nozomu Hirose
Keyword(s):  
Soil Moisture ◽  
Control Strategy ◽  
Satellite Remote Sensing ◽  
Meteorological Data ◽  
The State ◽  
Temperature And Precipitation ◽  
Set Up ◽  
Protection And Control ◽  
And Control

The desertification to Chinas Beijing-Tianjin area is analyzed by using the state of vegetation, soil moisture and meteorological data that are collected by the satellites. The state of vegetation, soil moisture and long-term changes of temperature and precipitation in the selected study areas (that are near Beijing-Tianjin area) is analyzed and compared, from which the trend of desertification is predicted. Thus the effective long-term protection and control strategy can be set up.

Images of the Adversary: NATO Assessments of the Soviet Union, 1953–1964

2009 ◽  
Vol 11 (2) ◽  
pp. 89-116
Author(s):  
Evanthis Hatzivassiliou
Keyword(s):  
Soviet Union ◽  
North Atlantic ◽  
Study Groups ◽  
Military Force ◽  
The North ◽  
Nikita Khrushchev ◽  
The Soviet Union ◽  
Long Term Trends ◽  
Set Up

The article presents the analysis of the study groups set up by the North Atlantic Treaty Organization (NATO) to assess the non-military aspects of Soviet power and potential during the era of Nikita Khrushchev. Following Stalin's death, the Western alliance tried to form a comprehensive view of the strengths and weaknesses of the USSR's economy and political system. This was part of NATO's effort to adjust to the realities of a long Cold War, the outcome of which would not be decided by military force alone. The NATO reports were largely successful in describing the long-term trends of the Soviet economy and the weaknesses of the Soviet system. However, they usually failed to anticipate specific, though significant and potentially dangerous, initiatives of the Soviet regime. On balance they were a crucial input for NATO ministers, and their importance in the shaping of Western policies needs to be evaluated carefully.

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