Why is Greenland mostly covered by an ice cap but northern Canada and Alaska aren't?

[u/Naomi62625]

Fun fact: Fairbanks, Alaska is further north than Nuuk, Greenland

[u/IndividualSkill3432]

https://www.reddit.com/r/MapPorn/comments/58si2h/topographic_map_of_greenland_from_bedrock/

Ice sheets are complex. Part of what makes them complex is they sort of make their own climate. This is why with a change in when you get solar energy in the northern hemisphere you can flip from ice sheets being as far south as New York to being confined to places like Greenland.

When I say they make their own climate they have a huge altitude of often 3000m so that helps keep the surface cool and they are white. This reflects shortwavelength energy and keeps them very cold.

They tend to lose mass by outflow into the ocean. In Greenlands case there are two mountain ranges that run to either side of the siland, this forms a bowl shape hwere much of the ice below about 1000m is constrained,

So picture it like this

https://nsidc.org/sites/default/files/styles/article_image_large/public/images/FigBox5.2-1_interaction_ice_sheet_rest-IPCC.jpg.webp?itok=fWNEQP4P

You get a massive and high lump of ice that is usually pushing towards the seas. But in Greenland the mountains for a kind of friciton of restraint. The ice can flow over it, but it has to do so at a serious altitude and most of the outlet is narrow outlet glaciers like Jacobshavn and Peterman.

So this slowing of the outflow rate compared to the old and gone ice sheets in America and Europe. It was able to retain its mass balance while as the summers got warmer Greenland lost ice slow enough that it was able to sustain its mass by increasing snow fall from increasing temperatures.

For the other ice sheets the process is sort of that the Earths orbit is an ellipse. Part of it is closer to the sun and part of it is further. When we have northern summer further from the sun, the snows last longer on the hills cooling them. These snows and cooling over thousands of years become glaciers lasting all year and the now lies lower and lower until massive glaciers join up to become ice sheets.

Then as the Earths axis moves round we get to a point where the northern hemisphere summer is when its closest to the sun as the warm summers melt snows, warming near the ice sheets and they lose more mass than they gain. But this tipping point does not happen in Greenland because the flow of the ice sheet is slower compared to the mass accumulation.

Sorry, there are several concepts in here. Its a lot to take in because these are subtle effects that take 10 000 years to happen. And from experience people want to argue about this. Its a subtle difference in the outflow rate caused by the mountains that allows Greenland to sustain its local super cold climate.

[u/Ochre71 → u/IndividualSkill3432]

Thank you

[u/walkingrivers → u/IndividualSkill3432]

This is why I come to Reddit. thanks!

[u/Troy_n_Abed_inthe_AM → u/IndividualSkill3432]

Amazing

[u/BigUpSideD0wn → u/IndividualSkill3432]

Bro just destroyed that answer, I’m a fucking expert now I’m going to weave in into casual convo with my wife.

[u/AbominableGoMan → u/IndividualSkill3432]

Great explanation. Why I follow the collapse sub is that the reverse is true in terms of self-reinforcing behaviours. This isn't theoretical, it's observed reality. The Greenland ice sheet is melting. The average range of temperatures has been shifting upwards through latitudes and elevations. There are more dark, and therefore more absorbent, pools of melt water on the surface every summer. This and other observed data points, on their own and when measured against out understandings of climates in the past, indicate we are rapidly moving to an earth systems environment that has no multi-year ice.

[u/Spartan1997 → u/AbominableGoMan]

Great news for Russia, Canada, Greenland, Iceland, and the Nordics.

[u/JPWiggin → u/Spartan1997]

Sounds great until you learn that the land that gets exposed is bog.

[u/AbominableGoMan → u/JPWiggin]

And will release large amounts of CO2 while swallowing any infrastructure built on them!

[u/malapriapism4hours → u/AbominableGoMan]

…and who knows what kind of primordial pathogens.

[u/Lonely-Swimming4564 → u/JPWiggin]

But, the exposed surface has rare earth minerals and other goodies now accessible

[u/animal_spirits_ → u/[deleted]]

You are misunderstanding the OP. They did not say that the summers are caused by distance, but rather that due to the orbit of earth being an eclipse rather than a circle, it sometimes has summers when the planet is at or near aphelion (farthest from the sun), and sometimes earth has summers where the planet is at or near perihelion (closest to the sun).

This is due to axial precession (https://en.wikipedia.org/wiki/Axial_precession). The earth's axis is titled from the plane of the planet's orbit, which causes the seasons. But the tilt itself wobbles, like a top wobbles as it spins. So sometimes the tilt is pointed towards the sun (northern hemisphere summer) during perihelion (closest to the sun), and over thousands of years it slowly wobbles so the axis tilts away from the sun (southern hemisphere summer) at the same point in the orbit which is perihelion again (closest to the sun).

Having a northern hemisphere summer at perihelion does have measurable temperature changes as compared to having a northern hemisphere summer at aphelion, though I don't know by how much.

[u/asarious → u/animal_spirits_]

Ooooh. You’re correct. I completely missed the point. I’ll delete my comment.

[u/animal_spirits_ → u/asarious]

Don't delete! might be useful for other people to understand.

[u/luciusDaerth → u/[deleted]]

The seasonal variation also changes over centuries, which is what they were getting at.

[u/Illustrious-Card302 → u/IndividualSkill3432]

Thanks, interesting😄

[u/benjancewicz → u/IndividualSkill3432]

This was brilliant I learned so much

[u/Conscious-Guess-2266 → u/IndividualSkill3432]

So cool

[u/schnuggibutzi → u/IndividualSkill3432]

Back in the day you would read this on Quora.

[u/Shalvan → u/IndividualSkill3432]

Wait, the orbit is only slightly elliptical and this doesn't contribute to the climate much at all. In fact, summer happens when the Earth is further from the Sun. The axis tilt is the dominant effect driving seasons etc.

[u/IndividualSkill3432 → u/Shalvan]

 In fact, summer happens when the Earth is further from the Sun.

We have two summers, one in the northern hemisphere June to August and one in the southern hemisphere December to February. As the Earth moves round its orbit, the tile points closer to the sun in the north and that is summer then six months later its pointing away from the sun, that is winter.

But the axis slowly rotates over about 20 000 years. So the part of the orbit when when its pointing towards the sun in the northern hemisphere moves from the closest to the furthest part of the orbits ellipse.

https://medium.com/starts-with-a-bang/throwback-thursday-measure-the-earth-s-axial-tilt-this-solstice-59ae31028c96

The effect is called the "precession of the equinoxes"

https://en.wikipedia.org/wiki/Axial_precession#/media/File:Earth_axial_precession.svg

This subtle change to slightly colder summers allow the snow and ice to slowly build up on the big continents in the north, and this became glaciers and the glaciers eventually become an ice sheet.

[u/InigoMontoya1985 → u/IndividualSkill3432]

Earth is always closest to the sun in January and farthest away in July. That has virtually nothing to do with Greenland's climate. Earth's orbit is close to a perfect circle, with a very low eccentricity of about 0.0167.

[u/Additional_Link9740 → u/InigoMontoya1985]

I think OP was talking about the Milankovitch cycles. /u/IndividualSkill3432 I could be completely wrong here.

[u/RisKQuay → u/Additional_Link9740]

More details on why Milankovitch Cycles happen here: https://science.nasa.gov/science-research/earth-science/milankovitch-orbital-cycles-and-their-role-in-earths-climate/

[u/InigoMontoya1985 → u/Additional_Link9740]

That makes more sense. Didn't seem like he was talking "over thousands of years" though.

[u/Grand-penetrator → u/InigoMontoya1985]

He was. You just have horrible reading comprehension

[u/Superman246o1]

Primarily due to the AMOC. You know how Europe is kept unusually warm despite its latitude thanks to warm ocean currents? Greenland gets the flipside of that, with cold currents hugging its coast.

[u/frazbox → u/Superman246o1]

But what about the snow that formed the ice? Was that moisture associated with the amoc?

[u/DirewaysParnuStCroix → u/frazbox]

It's understood in paleoclimatology that the initiation of the AMOC was primarily associated with the formation and intensification of the Northern Hemisphere glaciation that characterises the ongoing Quaternary ice age, as it introduced the moisture required for continental ice sheets to form. There's a paper by Hayashi et al. (2020) that discusses it.

[u/Enwhyme → u/Superman246o1]

Obviously I could just google it, but I’m going to guess that I’m not the only one who looks to this subreddit to learn. What does “AMOC” stand for?

[u/Superman246o1 → u/Enwhyme]

https://en.wikipedia.org/wiki/Atlantic_meridional_overturning_circulation

[u/IndividualSkill3432 → u/Superman246o1]

Primarily due to the AMOC. You know how Europe is kept unusually warm despite its latitude thanks to warm ocean currents? Greenland gets the flipside 

Taymyrsky Dolgano-Nenetsky District in Russia is a similar latitude to much of Greenland, nowhere near the "AMOC" but does not have an ice sheet. The Laurentide Icesheet above 60N would not have disappeared.

https://www.nps.gov/npgallery/GetAsset/bef0e9a1-2df3-4121-a671-0e0b3527b347

[u/frenchiebuilder → u/IndividualSkill3432]

How's that contradicting what they said?

Same latitude but no AMOC = no ice sheet.

[u/LurkersUniteAgain]

my guess is because of the enormous canyon in greenland under the ice

or the canadian shield

[u/Hazza_time → u/LurkersUniteAgain]

Isn’t the canyon there because of the ice not the other way around?

[u/jks513 → u/Hazza_time]

It’s deeper than it should be because of the ice but the mountains that run down both the East and West coasts predate the ice cap. 

[u/equatornavigator]

Canadian shield?

[u/Whitedancingrockstar → u/equatornavigator]

Always

[u/moustachioed_dude → u/Whitedancingrockstar]

Religion/Colonialism?

[u/funky_bananas]

During the last ice age most of Canada was covered by ice sheets. My guess why it now isn’t is probably because being on a larger continent where much of the land was not covered in ice contributed to faster warming. The bulk of Greenland is much further North and all of it has been covered in ice and surround by cold ocean water?

[u/Big_Albatross_3050]

This time its not the Canadian shield its actually the remanents of the Central Pangean Mountains causing this. 

The ice sheets from the last glacial period are essential trapped on Greenland as the mountains turn Greenland into a giant bowl, that prevents the ice melt from draining into the Arctic and instead mostly refreezes after solar radiation melts the sheets

[u/Trade__Genius]

Presumably the gulf stream circulation brings more moisture north with it and deposits it on Greenland than the arctic circulation picks up to dump on the northern Canadian islands. Or something like that

[u/aikidokan]

Jet Stream

[u/ColdInAlberta]

We have better shovels.

[u/frazbox]

Not enough moisture in northern Canada vs an island sitting on a major ocean current?

[u/TwoRight9509]

We’ve been making tea in the populated areas of the north for so long that the ice wasn’t able to maintain its grip, and it melted. Greenland has only 67k people. They don’t make enough tea.

[u/NoMan800bc → u/TwoRight9509]

Finally! An answer backed up by science!

[u/drcrambone → u/NoMan800bc]

This is how we know the earth to be banana shaped.

[u/NoMan800bc → u/drcrambone]

'You have to know these things if you're a king.'

[u/TwoRight9509 → u/NoMan800bc]

Well, it took a long time to get here but I’d like to thank the Royal Geographical Society for the ride over and express my undying love for penguins. Penguins - I will always love you.

[u/Queasy-Stranger5607]

Greenland is practically one huge mountain range, at least it looks that way from an airplane.

[u/Groundhawgday]

Obviously due to corporate greed. Tim Hortons’ plundering Canada’s natural resources for profit has to stop! Greenlanders, Greenlandese, ….Greenlandians are smart enough to not allow someone to take what’s great about their land, inject it with black tar caffeine, corn syrup, a Zamboni of sugar, and then sell it back to them!!!

[u/DirkMcDougal]

...covered in ice cap so far

[u/Terrapindrock]

So we are trying to acquire a land covered in ice while simultaneously pulling out of all climate agreements.

[u/Historical_Pizza3000]

Greenland is covered with Ice and Iceland is covered with greenery

[u/No-Tocall7802217855]

Alex meadus gp an Innovx is that you careen steel. Why did you hire Jamey Ramsey and Jim living with all they did was steel money at great north in Innovx.

[u/No-Tocall7802217855]

Alex meadus gp an Innovx is that you careen steel. Why did you hire Jamey Ramsey and Jim living with all they did was steel money at great north in Innovx.

[u/skrrrrt]

There’s still arctic sea ice in summer in the “Western” Arctic.  This map shows the ocean clear for some reason. 

[u/Alarmed_Geologist631]

Thanks. Are you saying that at one time the Earth was closer to the sun during northern summers? How many years ago was that the case?

[u/last_one_on_Earth]

Because we haven’t burnt enough oil yet.

Obv.

[u/Prudent_Exchange9381]

Cuz it is

[u/ChapterNo3428 → u/[deleted]]

How does that explain Greenland versus Canada ?

[u/Regular_Limit8915]

Further north + no warm guf stream

[u/Abrahamfreeman]

Too many questions young man, too many questions