Guide Ice Flow

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"Ice Flow". Instruments: Synths, Percussion. Feel: Grooving, Intense. This is another piece where the Feel descriptors don't work all that well.
Table of contents

• Glaciologists Unveil Most Precise Map of Antarctic Ice Flow
• British Columbians & Our Governments
• THE ASHER SLIM FIT

Sliding velocity is controlled by basal shear stress and effective pressure, which is the difference between ice overburden pressure and water pressure Jiskoot et al. Subglacial till see Glacial Processes comprises unconsolidated, unsorted or poorly sorted sediments ranging from boulders to clay. In Norfolk, till sequences are over 20 metres thick. Fine sediments, such as clay and sand, are not cohesive and therefore deform readily when shear stress is applied to them if they have a high pore-water pressure so, like basal sliding, subglacial deformation depends on high basal water pressures.

If basal shear stress the gravitational driving dress is greater than the yield strength of the till, deformation occurs, resulting in some fantastic glaciotectonic sequences see picture gallery below and papers by Davies et al. Glaciers do not just flow in a steady state, however. We have cold-based glaciers , which have little flow velocity; polythermal glaciers, which are partly frozen to their bed; wet-based glaciers which have sheet flow as is described in the above sections ; ice streams , which have very rapid flow velocities; and surging glaciers , which have periods of rapid flow separated by quiescent periods of slow flow.

The key differences in temperate glacier flow is summarised in the table below. Each of these different flow regimes results in a set of different and diagnostic glacial landforms. Go to top or jump to Glacier thermal regime. References Davies, B. Dynamic Devensian ice flow in NE England: a sedimentological reconstruction.

Boreas , Davies, B. Quaternary Science Reviews , Jiskoot, H. Singh, P. Singh, and U. Haritashya, Editors. Pingback: How Does a Glacier Move? Matt Chernos. The road to a PhD Save my name, email, and website in this browser for the next time I comment. This site uses Akismet to reduce spam.

• Robbins Basic Pathology E-Book (Robbins Pathology).
• Ice streams.
• The Fireside Chats?

Learn how your comment data is processed. Glacier mass balance Glacier flow Internal deformation Basal sliding Subglacial deformation Different types of glacier flow References Comments Glacier mass balance Components of mass balance of a glacier. Boulder pavement at Whitburn Bay, County Durham. The boulders represent an erosional surface between two glacial tills. Carboniferous limestone boulder in till at Whitburn Bay.

The boulder is shaped by glacial erosion and scratched by contact with other rocks and ice. Channel of sand and gravel deposited at the ice-bed interface. Two tills rest on top of Magnesian Limestone bedrock at Whitburn Bay, overlain by deformed glaciofluvial sands sands deposited by a proglacial river. Note the large, faceted boulders at the boundary between the two tills. Folded and deformed sands overlying glacial till at Whitburn Bay, County Durham. This sand was deposited in front of the glacier proglacial , but then overridden by the ice.

Complexly interbedded, folded and deformed sands in Middle Pleistocene sediments at Warren House Gill. Deformed and faulted chalk clasts in Middle Pleistocene glacial tills in North Norfolk, indicating brittle deformation. Soft chalk clasts have been strectched and folded here in north Norfolk by glacial processes. Rafts of chalk have been thrust up on top of one another within glaciotectonised sediments in north Norfolk.

Share this. If you enjoyed this post, please consider subscribing to the RSS feed to have future articles delivered to your feed reader. Leave a Reply Cancel reply Your email address will not be published. An ice sheet whose base is above sea level is a terrestrial ice sheet; one with its base below sea level still in contact with the bedrock is called a marine ice sheet. A marine ice sheet is susceptible to changes in the ocean temperature as well as changes in air temperature.

The West Antarctic Ice Sheet is a mainly marine ice sheet, so is very vulnerable to small changes in ocean temperature. Some studies have suggested that an ice sheet can never be in a steady state on a reverse slope, once the ice sheet reaches a reverse slope, retreat cannot be reversed. Some studies disagree with this, however, suggesting that the presence of an ice shelf may help to stabilise a marine ice sheet on a reverse slope. In reality, an ice sheet is a single entity, rather than a set of blocks.

We have to consider the ice as blocks in order to solve the equations for ice flow over space. The ice is represented in the game with a layered texture. The radar is able to see through the ice, picking up changes in the properties of the ice it is travelling through. The layers represent changes in the make up of the ice. Ice with no impurities is completely clear, however, ice can appear a number of different colours depending on its composition and how you are looking at it! Ice streams are like giant rivers of ice. Like rivers, ice flow organises itself into tributaries and fast flowing main channels.

The ice streams drain the majority of the ice from the ice sheet, and changes in their behaviour can have massive impacts on the whole ice sheet. Ice streams can flow at s metres per year in Antarctica, compared with interior ice which flows at a few metres per year. Each level in the game represents an ice stream which drains the Antarctic Ice Sheet. The bedrock elevations beneath each ice stream vary in depth and shape, which means each ice stream will respond differently to the same change in ocean temperature.

A model of this format does not give a full representation of ice flow, hence, modellers now use 3D models of ice flow to capture the full complexity. The bedrock profiles for each ice stream are a simplified representation of what is actually present beneath each ice stream. The resolution of an ice sheet model is an important consideration as small scale lumps and bumps may help to stabilise a retreating ice sheet. At this point it starts to float, this floating part is called an ice shelf it looks a bit like a shelf you might put a book or a picture frame on!

British Columbians & Our Governments

The point at which it starts to float is called the grounding line. Ice shelves are susceptible to changes in the ocean and the atmosphere, they have a relatively low surface elevation, so temperatures are warmer. An extreme example of the impact of climate change on ice shelves was the collapse of the Larsen B Ice Shelf on the Antarctic Peninsula. It is believed that meltwater ponds exacerbated crevassing on the ice shelf, and this led to collapse of the ice shelf, and speed up of the ice streams that flowed into the ice shelf.

Land above sea level, provides the source of friction at the sides of the ice shelves. This in turn provides the buttressing effect of ice shelves. In the model, the mountains are a graphical representation of some of the mountain ranges present adjacent to the ice streams. So the presence of a mountain range in the view may not be completely representative of the location of the mountains. An iceberg in itself is a normal part of an ice sheet life cycle, however, it can cause great alarm in the media when a large amount of ice breaks off an ice shelf. If the ice front does not recover to its previous extent some time after the calving event, then it tells us that the ice front is retreating, and this is then when there is cause for concern.

Iceberg calving is a complex process, which we are still working on representing robustly in ice sheet models. It is a triggered by lots of different factors. In the game we simply remove a block when the ice shelf reaches a critical thickness, to give the penguin a spot to jump into the water. In the interior of the Antarctic Ice Sheet, air temperatures are very cold, so a small amount of air temperature change will not significantly impact on the size of the ice sheet directly.

It is the indirect effects that cause big changes in the ice sheet, such as changes in ocean circulation. Ocean water around the planet varies in its temperature and saltiness salinity. This changes its density, which helps cause ocean currents to form. When the water is dense it sinks, so these currents form at different levels in the ocean. Wind blowing across the surface of the ocean also helps to drive ocean currents, and changes in the wind can modify ocean currents that will impact on marine ice sheets. At the edges of the ice sheet, and under the ice shelf, the water is very cold and fresh as it is formed from melting ice.

This water is a few degrees warmer than the melted-ice-water, so if it comes into contact with an ice shelf, it will cause much higher melting of that ice shelf. Sometimes changing weather patterns cause wind directions and speeds to change, driving the water from the deep ocean to under the ice shelf.

A major impact of a warmer climate is a change in sea ice conditions. If the sea ice is reduced, the wind may have more ability to cause warmer water to flow beneath the ice shelves. While a small increase in air temperature will not have a big impact on the interior of the ice sheet, it does affect more coastal areas at lower elevations.

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• Ice-flow indicators.
• A Sharpened Arrow: Preparing an arrow for the Archers use!

The Antarctic Peninsula has seen some of the biggest rates of air temperature change in recent years, which has led to many ice shelves retreating and breaking up. Most notably, the Larsen B Ice Shelf broke up in over the course of a few weeks, leading to the ice flowing into the ice shelf speeding up. It is thought that meltwater ponds which formed on the surface helped to cause such a catastrophic break up. The full process of how climate change impacts on ice sheets is not represented in the game, it is only the result - an increase in melt rates from the warmer ocean water - which is represented.

As described above, the increase in water temperatures is triggered by changes in the whole climate system. The complexity of ocean currents beneath the ice shelf is also not represented in the game, this is a very complex system, and understanding the impact of changing ice sheet and ocean conditions is very challenging.