Property:Theory movie

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A
The flow of water in rivers over loose sediments can lead to self organizing patterns, such as the ripples presented in this simulation. Generally, as the strength of the flow of water increases, low-flow bed forms evolve from a flat surface, to ripples, and then dunes. As higher flows occur, anti-dunes and eventually pools and chutes form. For more information see the related papers: doi: 10.1002/wrcr.20457 doi: 10.1002/wrcr.20303 doi: 10.1029/2012WR011911  +
Liquid water is thought to move through alpine glaciers as diffuse and channelized flow, and is governed by the pressure field created by the weight of overlying ice. This 2-D model combines the governing equations for both types of flow to model the movement of water in the the Gornergletscher, an alpine glacier in Switzerland. A video of the talk Mauro Werder gave at the CSDMS 2013 annual meeting on glacial hydrology is available on the CSDMS website, https://csdms.colorado.edu/wiki/CSDMS_2013_annual_meeting_Mauro_Werder  +
In Arctic landscapes, recent warming has significantly altered geomorphic process rates. Along the Beaufort Sea coastline bounding Alaska’s North Slope, the mean annual coastal erosion rate has doubled from ~7 m/yr for 1955-1979 to ~14 m/yr for 2002-2007 (Mars and Houseknecht, 2007). Locally the erosion rate can reach 30 m/yr. We aim to understanding the processes that influence coastal erosion rates; since we want to predict the response of the coast and its adjacent landscape to a rapidly changing climate, with implications for sediment and carbon fluxes, oilfield infrastructure, and animal habitat. The evolution of the permafrost bluffs on the North Slope is controlled by three conditions: length of the sea ice free season, warming sea water and wave and storm surge. During the sea ice-free season, relatively warm waters melt a notch into the ice-rich silt that comprises the 4-m tall bluffs. The bluffs ultimately fail by toppling of polygonal blocks bounded by mechanically weak ice-wedges that are spaced roughly 10-20 m apart. The toppled blocks then temporarily armor the coast against further attack. The annual coastal retreat rate is controlled by the length of the sea ice-free season, water and air temperatures, and the wave history. Honoring the high ice content of the bluff materials, it is thought that subaerial melt plays a minor role, and that the notching of the base of the bluff acts as an melting dirty ice berg. In quantitative iceberg melting models the local instantaneous melt rate goes as the product of the temperature difference between seawater and bluff material, and the wave height. Calculated instantaneous melt rate can be adjusted to account for the ambient temperature of the permafrost and the presence of non-ice material in the bluffs. Once a block is sufficiently undercut to become unstable it will fail and topple. The latter process can be described as a torque balance.  +
Sea ice has retreated far into the Arctic Ocean in the last few years, with 2007 being record low over the last 30 years. The animations shows the evolution of sea ice through winter-spring-summer and fall for 2009, which was the secondmost low year.  +
Erosion rates along permafrost coastlines of Alaska’s North Slope have been increasing over the past few decades (from 1953 onwards). The coast around Drew Point, roughly between Point Barrow and Prudhoe Bay along the Beaufort Sea, consists of ice-rich bluffs of about 3-5m high. Thermal energy accounts for most of the erosion potential along these ice-rich permafrost coastlines, so predictive models of coastal erosion require an understanding of how sea-ice and sea surface temperatures evolve, both through the summer ice-free season and interannually. To describe patterns of nearshore SST in the Beaufort Sea a team of USGS, INSTAAR and the Naval Postgraduate School deployed wave and ocean temperature sensors offshore from the National Petroleum Reserve in Alaska (NPR-A) during the summer of 2009. These sensors were placed in a shore-normal array between 0.2 and 10 km offshore, in water depths ranging from ~1m to 7m. Second, data is available from meteorological stations on the Alaskan North Slope to summarize the regional weather patterns that drive observed changes in ocean waves and temperatures over this time period. And lastly, we use satellite data to summarize sea ice position and sea surface temperatures over the past decade. As long as the sea ice is still hugging the coast, which can be upto Halfway July, erosion is very limited. Subsequently, early in the summer when sea ice remains near the coast, the nearshore open water area is sheltered from mixing and warms to its highest temperatures of the summer. Water nearshore can become very warm, up to 10 degrees C, and consequently high thermal erosion occurs along the coast. As the sea ice margin retreats in mid-summer, summertime storsm homogenizes the temperatures offshore, collapsing the offshore temperature gradient to less than 0.5 degrees C per km and dropping the nearshore temperatures by almost 5 degrees C. Thermal erosion potential is consequently reduced later in the summer. In the Fall season the sea surface water temperature drops to about 2 to -1 degrees C and there may be less potential for erosion.  
B
Barrier Islands migrate over the shelf in response to sea level changes. The island first progrades outward, during sea level fall and then retrogrades when sea level is coming up again. A elaborate discussion on classification can be found here: http://science.howstuffworks.com/environmental/conservation/issues/barrier-island.htm  +
Bed load transportation is a function of the fluid force per area, or shear stress on the stream bed. Shear stress is proportional to the specific weight of the fluid, the depth and the surface slope of the fluid. The frictional resisting force is proportional to the specific weight of the sediment and the diameter of the sediment.  +
Bed load transportation is a function of the fluid force per area, or shear stress on the stream bed. Shear stress is proportional to the specific weight of the fluid, the depth and the surface slope of the fluid. The frictional resisting force is proportional to the specific weight of the sediment and the diameter of the sediment.  +
Bed load transportation is a function of the fluid force per area, or shear stress on the stream bed. Shear stress is proportional to the specific weight of the fluid, the depth and the surface slope of the fluid. The frictional resisting force is proportional to the specific weight of the sediment and the diameter of the sediment.  +
Braided steams can occur in drainage basins that have high sediment content and/or in river environments that rapidly change channel depth and thus velocity such as alluvial fans, river deltas and peneplains.  +
Braided steams can occur in drainage basins that have high sediment content and/or in river environments that rapidly change channel depth and thus velocity such as alluvial fans, river deltas and peneplains.  +
C
Duperret et al. (2002) recently discussed bluff failure at Puys, 75 km to the northeast of the site of the video, Saint-Jouin-Bruneval. In that case they concluded that increased groundwater flow after heavy rain facilitated the collapse. Coastal Rock Cliff Erosion by Collapse at Puys, France: The Role of Impervious Marl Seams within Chalk of NW Europe Anne Duperret, Albert Genter, Rory N. Mortimore, Baptiste Delacourt and Mick R. De Pomerai Journal of Coastal Research , Vol. 18, No. 1 (Winter, 2002), pp. 52-61  +
With the inclusion of coastal processes the fluvial sediment becomes less stratified than when coastal processes that result in mixing aren't present.  +
Confluences are a common element of river networks, especially in the lower reaches and the deltaic floodplain. They are characterized by large-scale turbulent motions. Confluences are even more common in braided river networks, and play an important role in reworking and transporting bedload material.  +
D
A debris flow is a fast moving mass of unconsolidated, saturated debris that looks like flowing concrete. They differentiate from a mudflow by terms of the viscosity of the flow. Flows follow a steepest descent generally, although they are known the “climb” opposite valley walls in extreme cases. The front of the debris flow, or the toe, forms a lobe, marking flow front. This lobe often contains a great deal of the larger sediments including cobbles and boulders. Early pulses or previous debris flows form levees that channel the flow until they are breached. The presence of older levees indicates the recurrence and characteristics of debris flows in a particular area. This can be an important indicator of past debris flow activity for developing land on alluvial fan terrace surfaces. But, flows can carry clasts ranging in size from clay particles to boulders, and may contain woody debris. During later phases of the event, more viscous mud that contains sands, silts, and fines runs through the flowpath. Debris flows can be triggered by large amounts of rainfall, snow melt, or glacial/permafrost melt, or a combination of all. Speed of debris flows can vary from 0.5 m/s to 16 m/s in extreme conditions. Variables in the conditions that affect debris flow characteristics are slope, available sediment and vegetation in the flowpath. Debris flow are extremely destructive to life and property. This particular event happened on July 2nd, 2006. This is during the middle of the Southern Hemisphere's Austral Winter, but the temperature was unseasonally high at 32º C! It was the warmest July day ever recorded (pers. comm. W. Keller). This debris flow event is attributed to hydrothermal alteration of the local mountain flank and the melting of permafrost.  +
Fluvial system alternates between sediment storage and release due to autogenic slope fluctuations on the deltaic surface. Shoreline progradation rates increase during release events and slow during sediment storage. This process is entirely autogenic (internally generated, i.e., no external controls were changing to induce this process).  +
E
Basin and Landscape Dynamics (Badlands) is a parallel TIN-based landscape evolution model, built to simulate topography development at various space and time scales. The model is presently capable of simulating hillslope processes (linear diffusion), fluvial incision ('modified' SPL: erosion/transport/deposition), spatially and temporally varying geodynamic (horizontal + vertical displacements) and climatic forces which can be used to simulate changes in base level, as well as effects of climate changes or sea-level fluctuations.  +
F
This movie loops through sea ice concentration in the Chukchi and Beaufort Sea. Sea ice concentration (SSC) is measured by satellites on a daily basis. SSC has been measured from 1979 onwards, and thus provides us with a relatively long time-series to assess changes in the Arctic climate. The animation loops through the year 2007, which was a relatively warm year with a low sea ice minimum. The presence of sea ice impacts the time that waves and storm surge can affect the coast. Another parameter that affects waves and storm surge is the fetch-the distance that wind blows over open water. Here we show how we calculate each day the distance to the sea ice edge over all relevant directions (the grey lines). Then we pick the the average wind direction measured at the Barrow airfield for that day, and determine the fetch length in that specific direction (the red line).  +
G
A calving glacier (also called tidewater glacier) is a glacier that ends in a body of water. Calving glaciers occur in Alaska, Arctic Canada, Patagonia, as well as along the Greenlandic Ice Sheet and Antarctica. It is these systems that produce icebergs floating in the world oceans. Calving glaciers behave very differently than land-based glaciers. Their velocity accelerates at the terminus, and they are much more dynamic than land-based glaciers. Calving glaciers need a large accumulation area to compensate for the ice mass lost by calving. Calving rates of tidewater glaciers in Alaska were found to be controlled by the depth of the water at the glacier front (Brown et al., 1982). Vc=CHw+D Vc = calving speed (m/yr) C = calving coefficient (27.1 +/- 2 per yr for a study of 13 Alaskan glaciers) Hw = water depth at the glacier front (m) D = constant (0 m/yr for a study of 13 Alaskan glaciers) Calving glaciers can advance and retreat at great rates. Some of the Alaskan calving glaciers retreated over > 100 km in the last two centuries.  +