Diandong Ren

Insights into spatial sensitivities of ice mass response to environmental change from the SeaRISE ice sheet modeling project I: Antarctica

Sophie Nowicki, Robert A. Bindschadler, Ayako Abe-Ouchi, Andy Aschwanden, Ed Bueler, Hyeungu Choi, Jim Fastook, Glen Granzow, Ralf Greve, Gail Gutowski, Ute Herzfeld, Charles Jackson, Jesse Johnson, Constantine Khroulev, Eric Larour, Anders Levermann, William H. Lipscomb, Maria A. Martin, Mathieu Morlighem, Byron R. Parizek, David Pollard, Stephen F. Price, Diandong Ren, Eric Rignot, Fuyuki Saito, Tatsuru Sato, Hakime Seddik, Helene Seroussi, Kunio Takahashi, Ryan Walker, and Wei Li Wang

Mudslide-caused ecosystem degradation following Wenchuan earthquake 2008

[1] We have applied a scalable and extensible geo-fluid model (SEGMENT) that considers soil mechanics, vegetation transpiration and root mechanical reinforcement, and hydrological processes to simulate two dimensional maps of the landslides occurrence following the 2008 Wenchuan earthquake. Modeled locations and areas generally agree with observations. The model suggests that the potential energy of earth was lowered by 1.52 x 10 15 J by these landslides. With this, the vegetation destroyed transfer ∼235 Tg C to the dead respiring pool and transforms 5.54 × 10 -2 Tg N into unavailable sediments pools and the atmosphere. The cumulative CO 2 release to the atmosphere over the coming decades is comparable to that caused by hurricane Katrina 2005 (∼105 Tg) and equivalent to ∼2% of current annual carbon emissions from global fossil fuel combustion. The nitrogen loss is twice as much as that released by the 2007 California Fire (∼2.5 x 10 -2 Tg). A significant proportion of the nitrogen loss (14%) is in the form of nitrous oxide, which can affect the atmospheric ozone layer.

Landslide Risk Analysis using a New Constitutive Relationship for Granular Flow

Abstract In this study, landslide potential is investigated, using a new constitutive relationship for granular flow in a numerical model. Unique to this study is an original relationship between soil moisture and the inertial number for soil particles. This numerical model can be applied to arbitrary soil slab profile configurations and to the analysis of natural disasters, such as mudslides, glacier creeping, avalanches, landslips, and other pyroclastic flows. Here the focus is on mudslides. The authors examine the effects of bed slope and soil slab thickness, soil layered profile configuration, soil moisture content, basal sliding, and the growth of vegetation, and show that increased soil moisture enhances instability primarily by decreasing soil strength, together with increasing loading. Moreover, clay soils generally require a smaller relative saturation than sandy soils for sliding to commence. For a stable configuration, such as a small slope and/or dry soil, the basal sliding is absorbed if the ...

Predicting storm-triggered landslides

Abstract An overview of storm-triggered landslides is presented. Then a recently developed and extensively verified landslide modeling system is used to illustrate the importance of two important but presently overlooked mechanisms involved in landslides. The models adaptive design makes the incorporation of new physical mechanisms convenient. For example, by implementing a land surface scheme that simulates macropore features of fractured sliding material in the draining of surface ponding, it explains why precipitation intensity is critical in triggering catastrophic landslides. Based on this model, the authors made projections of landslide occurrence in the upcoming 10 years over a region of Southern California, using atmospheric parameters provided by a highresolution climate model under a viable emission future scenario. Current global coupled ocean–atmosphere climate model (CGCM) simulations of precipitation, properly interpreted, provide valuable information to guide studies of storm-triggered lan...

A Storm-Triggered Landslide Monitoring and Prediction System: Formulation and Case Study

Abstract Predicting the location and timing of mudslides with adequate lead time is a scientifically challenging problem that is critical for mitigating landslide impacts. Here, a new dynamic modeling system is described for monitoring and predicting storm-triggered landslides and their ecosystem implications. The model ingests both conventional and remotely sensed topographic and geologic data, whereas outputs include diagnostics required for the assessment of the physical and societal impacts of landslides. The system first was evaluated successfully in a series of experiments under idealized conditions. In the main study, under real conditions, the system was assessed over a mountainous region of China, the Yangjiashan Creeping (YC) slope. For this data-rich section of the Changjiang River, the model estimated creeping rates that had RMS errors of ∼0.5 mm yr−1 when compared with a dataset generated from borehole measurements. A prediction of the creeping curve for 2010 was made that suggested significa...

Three positive feedback mechanisms for ice-sheet melting in a warming climate

Three positive feedback mechanisms that accelerate ice-sheet melting are assessed in a warming climate, using a numerical ice model driven by atmospheric climate models. The Greenland ice sheet (GrIS) is the modeling test-bed under accelerated melting conditions. The first feedback is the interaction of sea water with ice. It is positive because fresh water melts ice faster than salty water, owing primarily to the reduction in water heat capacity by solutes. It is shown to be limited for the GrIS, which has only a small ocean interface, and the grounding line of some fast glaciers becomes land-terminating during the 21st century. The second positive feedback, strain heating, is positive because it produces further ice heating inside the ice sheet. The third positive feedback, granular basal sliding, applies to all ice sheets and becomes the dominant feedback during the 21st century. A numerical simulation of Jakobshavn Isbrae over the 21st century reveals that all three feedback processes are active for this glacier. Compared with the year 2000 level, annual ice discharge into the ocean could increase by ∼1.4 km3 a −1 (∼5% of the present annual rate) by 2100. Granular basal sliding contributes ∼40% of this increase.

The Greenland Ice Sheet Response to Transient Climate Change

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Temperate Mountain Glacier-Melting Rates for the Period 2001–30: Estimates from Three Coupled GCM Simulations for the Greater Himalayas

Abstract The temperate glaciers in the greater Himalayas (GH) and the neighboring region contribute to the freshwater supply for almost one-half of the people on earth. Under global warming conditions, the GH glaciers may melt more rapidly than high-latitude glaciers, owing to the coincidence of the accumulation and ablation seasons in summer. Based on a first-order energy balance approach for glacier thermodynamics, the possible imposed additional melting rate was estimated from three climate simulations using the Geophysical Fluid Dynamics Laboratory Global Coupled Climate Model version 2.1 (GFDL-CM2.1), the Model for Interdisciplinary Research on Climate 3.2, high-resolution version (MIROC3.2-hires), and the Met Office’s Third Hadley Centre Coupled Ocean–Atmosphere General Circulation Model (HadCM3). The simulations were carried out under the Special Report on Emissions Scenarios (SRES) A1B scenario. For the 30-yr period of 2001–30, all three CGCMs indicate that the glacial regions most sensitive to re...

The devastating Zhouqu storm‐triggered debris flow of August 2010: Likely causes and possible trends in a future warming climate

On 8 August 2010 in the northwestern Chinese province of Gansu, a rainstorm-triggered debris flow devastated the small county of Zhouqu. A modeling study, using a new multiple-phase scalable and extensible geofluid model, suggests that the cause is an intersection of several events. These were a heavy rainstorm, not necessarily the result of global warming, which triggered the landslide and followed a drought that created surface cracks and crevasses; the geology of the region, notably the loess covering heavily weathered surface rock; and the bedrock damage, that deepened the surface crevasses inflicted by the 7.9 magnitude Wenchuan earthquake of 12 May 2008. Deforestation and topsoil erosion were critical contributors to the massive size of the debris flow. The modeling results underscore the urgency for a high-priority program of revegetation of Zhouqu County, without which the region will remain exposed to future disastrous, “progressive bulking” type landslides. Debris flows are more predictable types of landslides; consequently, a series of “pseudo climate change” model experiments of future extreme precipitation events are carried out using the Weather Research and Forecasting model, forced by temperature perturbations from an ensemble of climate models. In a possibly future warmer climate, extreme precipitation events are anticipated to be more severe, and this study has identified an atmospheric blocking pattern that might produce future extreme precipitation events in the peri-Tibetan Plateau (TP) area (located to the northeast of the TP). Importantly, observations from gravity field measuring satellites indicate that the larger geological environment of this region also is becoming increasingly unstable.

Sensitivity of Tropical Cyclone Tracks and Intensity to Ocean Surface Temperature: Four Cases in Four Different Basins

This study investigates the sensitivity of tropical cyclone (TC) motion and intensity to ocean surface fluxes that, in turn, are directly related to sea surface temperatures (SSTs). The Advanced Research version of the Weather Research and Forecast (WRF-ARW) model is used with an improved parameterisation of surface latent heat flux account for ocean salinity. The WRF-ARW simulations compare satisfactorily with the NCEP/NCAR reanalysis for atmospheric fields and remotely sensed precipitation fields, with the model providing details lacking in coarse resolution observations. Among four TCs investigated, except the one re-developed from a previous TC remnant, the stretching term dominates the relative vorticity generation, and a bottom-up propagation mechanism holds for the three TCs. For the Tropical Rainfall Measuring Mission (TRMM) precipitation, the spatial ranges are accurate but actual rainfall rates are significantly larger than those remotely sensed. This indicates the value of numerical simulation in quantitative rainfall precipitation estimation (QPE) for TCs. Sensitivity experiments are performed with altered SSTs and changes in tracks and intensity are examined. A TC-dependent threshold wind speed is introduced in defining total kinetic energy, a measure of TC intensity, so arbitrariness in domain setting is avoided and inter-basin comparisons are possible. The four TCs selected from different global basin show that the intensity increases with increasing SST. Within a domain, a power–law relationship applies. More important, warmer SST indicates a more rapid intensification, quicker formation and reduced warning issuance time for emergency services. The influence of SSTs on TC track is more complex and lacks a generic relationship. For the South Pacific basin, higher SSTs favour a more northerly track. These TCs occasionally cross continental Australia and redevelop in the southern Indian Ocean basin, affecting the resource-rich onshore and offshore industrial developments in northwest Western Australia. In the Atlantic basin (e.g. Katrina 2005), when SSTs increase, the TC tracks tend to curve over warm pools but generally have a shorter ocean-residence time. When the synthesised SST fields are raised 2°C above Katrina (i.e. >32°C), the possibility exists of generating two TCs in close proximity. That lack of unanimity of the impacts on TC tracks, in response to synthesised SSTs, partly arises from the complicated response of subtropical highs, which may be disintegrated into several pieces and dispersed with relatively lower pressure regions, which may become the shortcuts when a TC traces the periphery of the subtropical high.