Science vs Fiction

Ice Flows is based on science - but some elements are fiction in order to make the game fun to play. Here we separate the science from the fiction and give you some hints for answering some of the quiz questions in the game.

Click on the image below to find out more about different parts of the ice sheet!


Ice Flows - The Game

Science

The game is called Ice Flows - because it does! Ice behaves like a fluid and flows due to gravity, much like a blob of treacle does, though a bit slower…   Snow falls on the top of the ice sheet, and ice is lost at the edges and underneath through iceberg calving & melting.

If the inputs and outputs are equal, the ice sheet finds a balance – a “happy place” (or more scientifically, an equilibrium state), where the ice flows at a rate to balance these inputs and outputs.

The game is based on a simple ice sheet model which represents the way in which ice flows, and how that flow is altered by changes in the surrounding environment. Computer-based ice sheet simulation models are used by scientists to both understand how the ice behaves and to make projections for future behaviour.

Fiction

Ice flows slowly, from a few metres per year, to several metres per day. In the game, time and space are modified to make the game playable.

Time:

The game would take a very long time to play if we didn’t speed up time, the game time for one level represents thousands of years, though changes in ice sheets over decades can cause a significant contribution to sea level change.

Space:

If the height and length of the ice sheet were representative of the real ice sheet , you would need to line up a few hundred phones in order to see the whole ice sheet. Hence, the ice sheet has been stretched in height in comparison to its length. Each profile represents about 1500 kilometres in length, and about 4000 metres in height.

Ice flow:

Ice sheet models are very complex mathematical representations of ice flow, and are too complex to be programmed into a game people can play on a mobile phone. We have simplified the representation of ice flow to produce something that replicates the overall behaviour, but runs quickly on a phone. As a result, we have not attached any numbers to the sliders for the ocean temperature and snowfall as we don’t want people to think that this is producing any kind of projection for the future. It is merely there to demonstrate how an ice sheet works, and how it responds to changes in its environment.

We discuss our representation of ice flow on the blog: http://blogs.exeter.ac.uk/iceflowsgame/2016/05/07/how-ice-flows/

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Ice sheets

Science

Ice sheets build up over long periods of time, as snow falls and is compacted under the weight of snow falling on top. The compacted snow becomes ice and begins to flow. We can see the layers of ice building up in data from radar measurements. The deformation of these layers can tell us a lot about the ice sheet's behaviour.

Types of ice sheet:

Ice sheets grow on land and flow towards their coastal margins. If they are thick enough, the ice can ground in the water. 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.

Marine Ice Sheet Instability Hypothesis
Often the bedrock on which a marine ice sheet rests deepens inland, this is called a “reverse” or “retrograde” slope. An ice sheet which has this type of bed is vulnerable to the “Marine Ice Sheet Instability Hypothesis” where a small change in ocean temperatures may lead to a very large response from the ice sheet. 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.

Also, there are a number of other ways in which the effects may be offset, through an increase in snowfall, through internal variations in flow speed, or by a process where the bedrock “rebounds” due to the reduction in weight, reducing the slope.

Fiction

In our ice flow model, we represent the ice sheet as “blocks” which flow and stretch and melt as they flow. 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. This is to represent what a radar “sees” as it looks at the ice.

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!

More information

Fact Sheets:
British Antarctic Survey: https://www.bas.ac.uk/about/antarctica/geography/ice/
National Snow and Ice Data Center: https://nsidc.org/cryosphere/quickfacts/icesheets.html
Antarctic Glaciers: http://www.antarcticglaciers.org/antarctica/

Journal articles/news:
Antarctic model raises prospect of unstoppable ice collapse
Antarctic coast meltdown could trigger ice-sheet collapse

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Climate change

Science

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 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. In the deeper ocean around Antarctica there is an ocean current called Circumpolar Deep Water (CDW) which flows around the continent. 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. Sea ice forms a barrier between the wind and the ocean surface, damping the effect of the wind on the ocean currents. If the sea ice is reduced, the wind may have more ability to cause warmer water to flow beneath the ice shelves.

Ice shelf collapse:

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. 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 2002 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.

Fiction

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.

More information

Fact Sheets:
Antarctic Glaciers: http://www.antarcticglaciers.org/glaciers-and-climate/climate-change/
National Snow and Ice Data Center - Ice shelf breakup: https://nsidc.org/cryosphere/sotc/iceshelves.html
Intergovernmental Panel on Climate Change FAQ Brochure (30 MB) - FAQ 13.2 "Will the Greenland and Antarctic Ice Sheets Contribute to Sea Level Change over the Rest of the Century?": https://www.ipcc.ch/report/ar5/wg1/docs/WG1AR5_FAQbrochure_FINAL.pdf

Journal articles/news:
Vulnerable ice in the Weddell Sea
Stability of the West Antarctic ice sheet in a warming world

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Sea level

Science

The entire Antarctic Ice Sheet contains enough water to raise sea level by 58 metres. Much of this is in the larger “East Antarctic Ice Sheet”, where large parts of the bed are above sea level. The West Antarctic Ice Sheet is a largely marine ice sheet, however, so is vulnerable to changes triggered by changes in ocean circulation. If the West Antarctic Ice Sheet were to collapse it would raise sea level by about 3 metres. One part of the ice sheet collapsing, could trigger another part by raising global sea level and causing extra flotation in other parts of the ice sheet.

The floating parts - ice shelves and icebergs - have already displaced ocean water, so their melting doesn’t directly contribute to sea level rise. The input of freshwater to the ocean does, however, change the ocean’s overall density – it has been calculated that if all the ice shelves of Antarctica melted, it could raise sea level by a 3-5 centimetres. The Ronne-Filchner Ice Shelf contains about half of the ice shelf volume in Antarctica, so could contribute a few centimetres to global sea level if it melted.

Fiction

Sea level changes are not incorporated into the model, partly because, graphically, you wouldn’t see a few centimetres on the scale of the game domain. Also, a flowline model makes it difficult to calculate the sea level contribution from one system retreating as we can’t incorporate the knock-on effects of changes in other ice streams.

More information

Fact Sheets:
Antarctic Glaciers: http://www.antarcticglaciers.org/glaciers-and-climate/sea-level-rise-2/
Intergovernmental Panel on Climate Change FAQ Brochure (30 MB) - FAQ 13.2 "Will the Greenland and Antarctic Ice Sheets Contribute to Sea Level Change over the Rest of the Century?": https://www.ipcc.ch/report/ar5/wg1/docs/WG1AR5_FAQbrochure_FINAL.pdf

Journal articles/news:
Potential sea-level rise from Antarctic ice-sheet instability constrained by observations

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Ice Streams

Science

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 100s 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.

Fiction

We only consider ice flow along a “flowline”, in one direction, in reality the ice flow is much more complex, with changes either side of the flowline having an impact. 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.

More information

Fact Sheets:
British Antarctic Survey: https://www.bas.ac.uk/about/antarctica/geography/ice/
Antarctic Glaciers: http://www.antarcticglaciers.org/modern-glaciers/ice-streams/

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Ice shelves & Grounding lines

Science

As ice flows faster near the edges of a marine based ice sheet, it thins and eventually isn’t thick enough and, hence, heavy enough to ground on the bedrock anymore. 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!). The point at which it starts to float is called the grounding line. Ice shelves play an important role in moderating ice stream flow, the friction on the sides of an ice shelf “buttress” the ice streams, like buttresses stop cathedral walls from collapsing.

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.

Fiction

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. Because we always have ice flow from left to right in the game, we wouldn’t always see the mountain ranges that are behind our view point. So the presence of a mountain range in the view may not be completely representative of the location of the mountains.

More information

Fact Sheets:
British Antarctic Survey: https://www.bas.ac.uk/about/antarctica/geography/ice/
National Snow and Ice Data Center: https://nsidc.org/cryosphere/quickfacts/iceshelves.html
Antarctic Glaciers: http://www.antarcticglaciers.org/modern-glaciers/ice-shelves-sea-ice-icebergs/#SECTION_1

Journal articles/news:
Antarctic Ice Safety Band at Risk
Antarctic ice-sheet loss driven by basal melting of ice shelves

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Icebergs

Science

As the ice in an ice shelf stretches and thins, it becomes weak, and eventually a lump of ice breaks off – an iceberg “calves”.

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. In Antarctica, icebergs can be huge, for example iceberg “A-38” broke off the Ronne Ice Shelf in 1998, measuring ~150 kilometres long and ~50 kilometres wide, covering an area of ~ 7500 km2, approximately three times the size of Luxembourg.

An important message this game aims to get across is that melting & iceberg calving are a normal part of an ice sheet that is in steady-state. Melting & icebergs become a source of concern when the amount of ice lost is greater than that going in, and the ice sheet becomes smaller and sea level rises.

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.

Fiction

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.

More information

Fact Sheets:
British Antarctic Survey: https://www.bas.ac.uk/about/antarctica/geography/ice/
National Snow and Ice Data Center: https://nsidc.org/cryosphere/quickfacts/icebergs.html
Antarctic Glaciers: http://www.antarcticglaciers.org/modern-glaciers/ice-shelves-sea-ice-icebergs/#SECTION_2

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Ice floes

Science

The game is called ice flows, a subtle play on words with the term “ice floes”. Confusingly, an ice floe is a section of sea ice. Sea ice is a different entity to glacial ice, being formed by frozen sea water. Sea ice tends to be a few metres thick, floating on the ocean, and comes and goes with the seasons, though some survives from one year to the next. Ice floes are not to be confused with icebergs which have broken off an ice sheet.

Fiction

Sea ice is not represented in the game, though it plays an important role in driving and changing ocean circulation.

More information

Fact Sheets:
British Antarctic Survey: https://www.bas.ac.uk/about/antarctica/geography/ice/
National Snow and Ice Data Center: https://nsidc.org/cryosphere/quickfacts/seaice.html
Antarctic Glaciers: http://www.antarcticglaciers.org/modern-glaciers/ice-shelves-sea-ice-icebergs/#SECTION_3

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Penguins

Science

The role of penguins in the game is very much focussed around the game play, so should not be considered an accurate portrayal of how penguins behave and how they might be affected by changes in ice sheets! See the fiction section below.

Penguins are mainly affected by changes in sea ice distribution, but can be affected by icebergs which affect sea ice distribution and block access to the water.

Penguins & sea ice:

Most Antarctic penguin species nest on rock, so losses of ice on land can create more breeding habitat. However, emperor penguins nest on fast ice (sea ice attached to land or ice shelves), and need this to be stable throughout the breeding season to raise chicks successfully. In some years ice breaks up earlier and all the chicks die.

Penguins breathe air but feed in the water, so extensive ice can act as a barrier to foraging. If there is too much ice around the colony birds may have to walk for miles to the ice margin find food. Walking is slower than swimming, and this can mean chicks are fed less often and grow more slowly/starve when too much ice is around the colony.

The prey species of penguins in the Antarctic include krill and icefish. These feed on algae and invertebrates under the sea ice, respectively, so a loss of sea ice can mean less prey for penguins. Some sea ice can also be useful to rest on whilst at sea (which saves energy) and to avoid predators (like leopard seals and killer whales). A mosaic of sea ice around colonies is therefore optimal to provide access to water, abundant prey and platforms to rest on. The optimal amount of sea ice varies among species: Adélies and emperors like sea ice, chinstraps tolerate it while gentoos tend to avoid it.

During winter, Adélie penguins and emperor penguins feed on the ice edge. If this marginal ice zone moves south due to ice melting, the day length available to forage gets shorter, and as penguins mostly forage during the daytime this may makes it harder for them to balance their energy budgets.

Penguins & icebergs

Breaking up of ice shelves can produce colossal icebergs that block penguins access to feeding areas, resulting in chick mortality and colony abandonment.

Penguins & Climate Change

Effects of climate on penguins are complicated and dependent on species and location. For example, Adélie penguins are declining in the Western Antarctic Peninsula owing to loss of sea ice, whilst gentoos are increasing. In contrast in East Antarctica loss of ice on land and expansion of sea ice (owing to reduced salinity from glacier melt, among other causes) is allowing Adélie populations to increase and it remains too cold for gentoos to colonise.

Long term projections suggest that Adélie and emperor penguins will move south to colonise areas that were formerly too icy for them to inhabit. However, the continental landmass imposes limits on how far south they can move, with the Ross and Weddell Seas providing the most southerly possible refuge. Their former range to the north will become colonised by more sub-Antarctic species like chinstrap, gentoo and macaroni penguins. Nonetheless, detrimental effects of ice loss on prey abundance and daylight foraging opportunities during winter may result in net losses of penguin biomass across the continent.

Fiction

Most of the penguin behaviour in the game is based on fiction, in order to generate the game play. Also, rainbow-penguins, dragon-penguins, dinosaur-penguins, unicorn-penguins and pheonix-penguins do not exist (say it quietly). The only reality is that penguins eat fish, and leopard seals eat penguins.

Penguins do not tend to go too far inland on an ice sheet as they need to be close to the water to feed, so they are not found flowing along on top of ice sheets.

It is not the case that shrinking ice sheets are good for penguins because they can get to fish under the ice shelf. Fish are not generally found underneath ice shelves, the penguins in reality feed under the sea ice (see Science section above).

More information

https://www.bas.ac.uk/about/antarctica/wildlife/penguins/

Journal articles/news:
Demographic models and IPCC climate projections predict the decline of an emperor penguin population
Predicting responses of the Adélie penguin population of Edmonson Point to future sea ice changes in the Ross Sea

so - make sure you can separate science from fiction!
The Guardian: 150000 penguins killed after giant iceberg renders colony landlocked
Live Science: Missing adelie penguins are probably fine
The Guardian: Missing penguins mystery 150000 birds feared dead may have relocated

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