glacier are disappearing around the major planet , and the questions of how scientists monitor glaciers and how these glaciers affect global sea spirit level wage hike are very important for the future tense .
ForThe Big Questions , IFLScience ’s podcast , we talk toDr Peter Davis , a physical oceanographer from the British Antarctic Survey to discuss these questions and his research on Thwaites Glacier in Antarctica .
How do you monitor the change in Methedrine shelves and glacier ?
Peter Davis ( PD ): There are two or three unlike way . The first and most indirect manner is through satellite automations . Whizzing around the major planet way up in space there are bunch of satellites that we use to observe the ice shelves . We can look at their heaviness , we can see at round-eyed imagery of them , and see how they ’re answer in time .
Then there ’s what I do – in - situ observance a.k.a . recondite fieldwork . We go to the meth shelves and theglaciersand we either observe them from the surface , or we take reflection of snow and weather . We employ seismic , using sound basically to understand the makeup and how thick they are .
We also observe the ocean underneath . Using proficiency sleep with as hot water oil production to exercise through the chalk shelf , we deploy instruments in the ocean cavity underneath the floating ice ledge . These official document let us supervise how the sea is deepen , how it ’s circulating , its temperature , and how the ice shelf is melting from underneath . We use all that selective information to build a picture of how the ice shelves and glaciers are evolve over time .
Why is it crucial to understand how the glacier or ice ledge is unfreeze from to a lower place ?
( PD ): fundamentally , the key idea is that glacier flow in off the continent ofAntarctica , like massive river of ice . They ’re very dull moving but they drift towards the ocean and when the ice that ’s on the background gets into the ocean , it causes ocean levels to rise .
Ice shelves , which are floating annexe of these glacier , play as a cork that holds back the ice that ’s on the land . They prevent the frappe from mother into the ocean and therefore they controlsea levelrise . The problem is when you melt an ice shelf from beneath , it weaken its ability to hold the ice back on the land and it let the ocean level cost increase to come about more chop-chop .
When we observe an ice shelf or glacier from the surface , what we are essentially calculate at is how the surface is shift . It ’s basically changing its tiptop , but that integrates a lot of dissimilar outgrowth , of which dethaw is just one part . We have to make a caboodle of supposition about the other appendage to determine how much of it is melting .
It ’s a much full , although certainly harder and more logistically intense , operation to go to the water ice shelf and observe its melt rate instantly , either using radars we put on the control surface or drill through and place instruments look up at it from below to measure the thaw charge per unit directly .
What are the change we are learn in Antarctica that are impact global ocean stratum rise ?
( PD ): We are seeing that warm water that is offshore of the Antarctic continent is being coerce onto the continental shelf and underneath the ice shelves more chop-chop . When methamphetamine hydrochloride shelf are in balance , the amount of ice or grounded ice-skating rink that baffle over the run aground blood – that ’s the point where the ice ledge first starts floating – agree the amount of ice that ’s lost through melting and calving of icebergs .
The problem is that we are acquire more warm water that ’s coming onto the shelves ; it ’s driving more melting from beneath and it ’s knocking ice shelves or glacier out of balance . This means that we ’re getting more trash from the land into the ocean , causing sea tier to rise .
Are there specific domain in Antarctica that are more moved than others ?
( PD ): Yes , West Antarctica . Antarctica is more often than not burst into two spacious expanse , East Antarcticaand West Antarctica . East Antarctica is much larger , but West Antarctica is the area we are most interested about , and this is because the warm water that ’s driving the ice shelf melting gets much closer to the continental shelf in West Antarctica than it does in East Antarctica .
In East Antarctica , for a variety of unlike reason , there ’s a lot of cold piddle on these continental shelves that essentially protect the ice shelves from the warm piss that ’s course around the continent . presently , our best observations show that warm water is n’t readily access East Antarctica icing shelves . Whether that continue into the futurity is an open motion but currently , West Antarctica is the area of most concern .
How much have things changed in West Antarctica ?
( atomic number 46 ): In footing of grownup , obvious changes , we ’ve seen a figure of ice shelves in the south-polar peninsula – which is kind of the boundary between East and West – collapse entirely . The Larsen A ice ledge has gone , and the Larsen B icing ledge has travel . They ’ve been collapsing from the North to the South as atmospherical temperature warm up , and then further around in the Amundsen Sea , we ’re seeing warm water thawing feedback . We ’ve seen grounding lines retreat very rapidly , 2 kilometers ( 1.2 mile ) a year . We ’ve see big calving events from the front of these glacier – frappe straw man have retreat inland .
Over what time full point have we insure these changes ?
( PD ): Probably over the last10 to 20 year . The problem is that we see a lot of individual consequence and then attribution [ to a particular time ] is actually quite difficult , but sure enough it ’s been a slow evolving operation . It was perhaps around the seventies or 1980s when we first lead off to smell out that this ardent water was coming onto the ledge .
We ’ve seen these successive event and excessive record retreats , but I do n’t think you may really point to one special period of fourth dimension when something vary or happened . It ’s an on-going cognitive process .
What complicates matters is that we make out the realm has these natural long - term cycles that take 10 years to go from one commonwealth to the next , and then back to the original state of matter . When we ’ve only been take note for 20 years , in particular not in situ , it ’s quite hard to find fault out from the observation precisely what started when .
Of of course , we havemodelsthat give us a much bigger movie and recount us why it ’s changing and how it ’s go to change , but picking out the ascription of those variety is more difficult .
Are you using the model to try and crop out the changes that are natural to Antarctica and its glacier , and those that might be attributable to anthropogenic climate warming ?
( PD ): unquestionably – there are already people working on that precise question . The expectant thing about computer models is you’re able to melt many different simulations with many unlike initial condition and the elbow room that we force the model .
One of the things that researchers can do is go the simulation using historical climate forcing without glasshouse gas emissions several time . That tell us something about the born variability in the system that we see and the benefit of that is knowing that what we see in the material world is only one instance of all possible cycles . It ’s a chaotic arrangement .
Then , they can redo all the pretending with greenhouse flatulence forcing and lead off to look at the conflict between all the different simulations . As they have n’t just done it once – they ’ve done it hundreds of time – they can get down to pluck out what ’s rude and what ’s not natural and start attributing variety to greenhouse gas emission , natural variation , and natural forcing .
You work specifically onThwaites Glacier . What kind of change have you seen there in the last decade or so ?
( PD ): Thwaites is split into two freestanding dynamical regions . We have the Thwaites independent trunk and we have the Thwaites Eastern Ice Shelf . The main trunk has disintegrated quite chop-chop into more of a loose mélange of these block of meth , whereas the Eastern Ice Shelf has retained more of an meth ledge structure . It has a more classical floating tongue that ’s out over the ocean , but even that is now start to break dance up . We ’re seeing boastful rifts and crack in the ice , across the frosting shelf ’s surface and all the grounds is pointing to a collapse of that icing shelf in the next 10 to 20 yr .
Do you recognise why there is a difference between these two theatrical role ?
( PD ): The answer has to do with the seabed topography . The ice shelves , once they float off the continent , can run across what is known as “ immobilise points ” . This is where you get shallow seabed topography that intersects with the ice base , and it produce a place for the ice to spellbind onto .
In front of the Eastern Ice Shelf , there remains a pinning point . The ice ledge is still thick enough that it can agree onto that ocean floor , and it can hold its form , whereas on the independent trunk , there is no longer a trap point . Essentially , what was the ice rink ledge has become unconstrained and it ’s just flown out into these openhanded occlusion .
If the collapse of this glacier happens in the next 15 or 20 years , what are we look at in terms of short - term and farseeing - term consequences , for both the glacier in West Antarctica and global sea levels ?
( PD ): To clarify , we ’re talking about the flop of the ice shelf – the drift bit – in 15 to 20 old age . Thecollapseof the glacier – the grounded bit – whilst possible , is certainly not something we are look to happen within 100 , 200 , or even 300 years . It ’s a multi - hundred to millennian timescale .
However , if the ice ledge cave in , we would instantly see a greater flux density of crank from the ground into the ocean . That would , in good turn , directly cause the rate of ocean level rise to increase . If , in the worst - case scenario , that triggered some sort of unstable collapse of the glacier that played itself out over many centuries , the sea stratum rising slope could be on the order of substructure , as the glacier go along to flow into the ocean .
There are suggestions that if the Thwaites Glacier was lose , that may destabilise wider parts of West Antarctica , the whole Amundsen Bay and Sea may become unstable , and then you ’re appear at really ruinous rate of sea horizontal surface rise . But , to stress again , this is not a decade - farseeing process – this is C to grand of years .
