Greenland ice loss caused about 40 percent of total sea level rise in 2019 | Hacker News Reader

Greenland ice loss caused about 40 percent of total sea level rise in 2019

phys.org

58 pointspseudolus9 comments

> enough to raise the global watermark 1.5 millimetres

How is it even possible to measure increases this small? Isn't there an unavoidable error range of at least centimeters?

You can probably get a pretty accurate measurement by integrating water pressure over time and taking an average, and you could probably reduce error further by using an array of pressure sensors.

But how do you account for water level going up and down on it's own just over a single day?

It's not a direct measurement. If you put 100 mL of water into a cup, it will raise the water level of the cup by some number of cm. You can calculate this based on the topography of the cup.

Similarly, we can calculate the volume of 600 btons of ice when turned into water, and we know the surface area the oceans, so we can calculate the ocean level rise of inserting 600 btons of ice worth of water into the oceans.

In addition, they do do direct measurements of ocean level. You can learn more about one way these measurements are performed here[1]. That direct measurement tells us the real rise each year. That in combination with the calculated measurement I describe above allows the scientists to conclude that the loss of ice mass in Greenland contributed about 40% of the total sea level rise in 2019.

[1] https://climatekids.nasa.gov/sea-level/

You could just average it out. The phase of any waves should be essentially random from day to day, so should average out quite quickly I imagine.

You don't take measurements over a single day, that's what I meant by integrating. You take measurements over a long period of time and analyze them.

They measured the loss of ice mass on Greenland with satellites, calculated the volume of water that it melted into, and calculated the rise in the ocean using the ocean's relative volume.

https://www.nature.com/articles/s41586-019-1855-2

What matters is the surface area of the oceans, rather than the volume.

Contra what others are saying: it's obviously not a measured increase, but an estimate based on calculated volume of ice. Assuming the paper they're referring to is this one:

https://www.the-cryosphere-discuss.net/tc-2020-89/

What's more, the "results" are entirely based on models rather than any empirical data.

Amusingly, another paper in the same journal published a few days earlier, uses models and empirical data to conclude that 2019 was a particularly weird year rather than any ominous thing: https://www.the-cryosphere.net/14/1209/2020/

This sort of "science by press release" is entirely unhelpful. People have completely bonkers views as to what CO2 induced warming will do to things like sea level. To the point where people (with ph.d.s in hard sciences even) have expressed concern when I bought a house a kilometer from a coastline that is 200 feet above sea level.

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