Antarctic Ice Shelf Demise | Hacker News Reader

Antarctic Ice Shelf Demise

esa.int

83 pointsgmays20 comments

So, if I'm reading the nifty infographic correctly, essentially all of the mass loss occurred between 1997-2000, and the total tonnage has remained consistent or even grown somewhat since 2000 (solid gray line in embedded timeseries chart in the first main figure). The article really tries to focus on the loss aspect, and the amount of ice lost between 1997 and 2000 is certainly shocking - nearly 10,000 gigatons in just a few years! But there hasn't really been any loss overall since about 2000. A complex picture, but maybe encouraging that things haven't deteriorated much over the last 20 or so years?

I wonder what the mass balance picture looks like when you add in the glaciers on land behind the ice sheets. It seems plausible that the ice shelves that seem be be stable or growing in size may be doing so simply because glaciers are moving out to sea faster than the edge of the ice shelves are calving, but I don't know if that effect is larger or smaller than the accumulation of new ice on the shelves.

Maybe we are looking at different charts, but the one I see says 1997-2021 and the individual glacier lines almost all trend downwards over the whole period.

It’s really not clear whether the mass balance graph (in the video) shows overall mass balance, or mass balance over time. I think it’s the latter, which would mean the _decline_ has been stable since 2000 (except for two fields which grew). From the study:

> Surface mass balance

> We estimate the SMB of each ice shelf at monthly time resolution using output from three regional climate models

I'm reading that chart as depicting the amount of mass lost per year, not the total remaining mass. So that means it's consistently losing mass every year

You're misreading it, it's YoY change. The shocking 10,000 gigatons is the new yearly baseline.

You're only looking at net numbers and not how it's an interconnected system and when one sheet goes so does it's support for those near it. Look at how significant the loss is on the west side. Read the article before speculating from your interpretation of a graphic please.

For anyone who just wants a lot of graphs, I really like this client scientists website: https://zacklabe.com/antarctic-sea-ice-extentconcentration/

Note that the graphs at the top of the page are extent (surface area) not volume. Volume graphs (as in the article) are at the bottom of the page... Graphs for global and arctic sea ice are on different pages.

How do current climate scientists reconcile reporting the relatively slow loss of glacial ice at both poles currently is something that’s unnatural, worrying, proof of humans destroying the planet, a doomsday scenario for life on earth… with the fact that North America was covered by a sheet of ice that was 2-3 kilometres thick only 20,000 years ago. A blink in geological time.

Disclaimer: Yes, human greenhouse gas emissions contribute to climate change etc etc. Yes we should be moving away from fossil fuels. I wholeheartedly agree with all the correct views. But even the most conservative napkin math on the average loss of ice that occurred long before humans were emitting with more than a few thousand campfires globally is orders of magnitude more than we observe now. And that ignores the fact that melt rate accelerates as mass decreases for ice, which would be expected if humans never existed in the first place.

https://xkcd.com/1732/

And when you extend it back to 120k years before present?

Or if you don’t use a smoothed averaged-sliding-window for everything except the most recent datapoints you’re trying to draw attention to?

> And when you extend it back to 120k years before present?

If you do that you realize we're approaching temperatures that the planet hasn't seen in about 5 million years. [0]

0. https://en.wikipedia.org/wiki/Geologic_temperature_record#/m...

https://en.wikipedia.org/wiki/Milankovitch_cycles?wprov=sfla...

> be expected if humans never existed in the first place.

Sans humans, surely the earth systems would be slowly creeping back towards more and more ice ... at least by the pattern of glacial advance and retreat in this current long term (million year) age of mini ice cycles.

But it's not, is it?

Instead the sea | earth surface layer is getting hotter, much hotter than expected and on a rapid (by geological time) scale.

This is entirely due to human activity as our population has rapidly expanded in the past 100 years and our resource consumption has exploded to match, dragging up carbon that took millions of years to lay down and more to bury deep.

The pressure this presents on human day to day existence is pressing down fast, we've become more and more dependant on daily movements of food and energy that are critically reliant on everything being "just so" - as much as we might kid ourselves we do not have robust supply chains that can rapidly adapt to the challenge of feeding a billion people if broad area cropping zones tip and become non productive for a decade or more.

Very few people are panicing about the fate of the planet on a thousand year time scale - it's a pretty rubust orbiting mass.

Sensible people are concerned about the future of humans on the scale of a hundred years.

It takes planning and coordination to ride such things out with minimal impact.

And how many people did that climate support?

I don't quite get what you're getting at. If North America froze under 3km of ice today, quite a few people would be annoyed. Life wouldn't go extinct, but it'd be harder to commute to work.

Similarly, climate change isn't a threat to life on earth as we know it, but it does inconvenience a few species. And asking people to move to another country because you drowned their island or burnt their city isn't a great way to make friends.

By and large the Earth is a big wet rock that suffers a variety of misfortunes from time to time, and it tends to suck for things living on it during those times. Climate change just happens to be one of those periods of unpleasantness, except this one is human caused and happens on a human timescale. If humans sent a asteroid hurting towards ourselves, to hit us in a few decades, you'd probably see a few protests and strongly worded science studies about that too.

> climate change isn't a threat to life on earth as we know it

But there is plenty of evidence that it is. Peter Ward has done some great work (and plenty of geologists agree) that most of the planets mass extinction events are triggered by rapid rises in CO2 leading to abrupt climate change and mass die offs.

The big difference with our current situation is that the CO2 is being released much faster than in previous extinction events.

Stepping aside all the hate one gets for being critical of a scientific theory (as we all should do, regardless of how well established it is), there is quite a bit of evidence that polar ice helps to regulate global temperature, seasonal extremes (both hot and cold), seasonal timings, and weather patterns. These are all things we rely on to feed the global population, and live in all the places we do.

As to your main question, I don't see the same conclusion from the data. "Relatively slow" to what? We do have a good understanding of how greenhouse gasses work, and the data for glacial loss is correlated with gas emissions very tightly. I should probably dive into the most up to date data rather than use nebulous words like "very" and "good", but my stance is built on quite a bit of research into it a decade ago while pursuing an Atmospheric Sciences degree, so unless there's been new information that completely changes our understanding, I'd say it still carries weight.

Please try to be more scientific in your posts, thanks!

Deep geological time isn't very relevant to human civilisations. The Fall Of Civilisations podcast has great long deep dives into what does threaten them, and the score is about 50:50 between climate change and Outside Context Problems.

Reply on news.ycombinator.com