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garrettdreyfus commented on Shrinking freshwater availability increasing land contribution to sea level rise   news.asu.edu/20250725-env... · Posted by u/ornel
perching_aix · 22 days ago
So let me get this straight:

- sea level is formally referred to as Global Mean Sea Level (GMSL)

- its change is segmented into two subcategories in literature(?), mass-driven (e.g. ice melting?, freshwater runoff?, freshwater water cycle stuff?) and non-mass-driven (e.g. thermal expansion?)

- freshwater loss from land was found to be at present the lead driver of the mass-driven change as per the paper (over what timeframe?)

- title says it's the primary driver for GMSL change overall, which this alone doesn't support (i.e. the title is a lie)

- @ornel (the person posting) points to another study that claims mass-driven change is the leading change, hence the title [0, this doesn't pass my smell test but i see the logic]

- you point out that that's glossing over that that other study is counting from 1900, but if one shrunk the evaluation window, the non-mass-driven causes would be the drivers now [1, this doesn't pass my smell test either, but i see the logic here as well]

The latter point then begs the question though, what is the time window in this case then, and how stable that result is? What would be an "appropriate" time window to choose, and how would one derive that?

Regarding my non-passing smell tests, imagine the following scenario for some event:

- category A: 51% of the total

- cause A1: 26% of the total

- cause A2: 25% of the total

- category B: 49% of the total

- cause B1: 27% of the total

- cause B2: 22% of the total

In this case, category A will be the lead contributor, but individually none of its contributing causes will be, addressing [0]. The causes will be ordered like so instead: B1 > A1 > A2 > B2. More elaborate variations are possible of course. For [1], you can imagine the same scenario just in reverse.

Did I get all this right?

garrettdreyfus · 22 days ago
I very much like your categories point here by the way!
garrettdreyfus commented on Shrinking freshwater availability increasing land contribution to sea level rise   news.asu.edu/20250725-env... · Posted by u/ornel
perching_aix · 22 days ago
So let me get this straight:

- sea level is formally referred to as Global Mean Sea Level (GMSL)

- its change is segmented into two subcategories in literature(?), mass-driven (e.g. ice melting?, freshwater runoff?, freshwater water cycle stuff?) and non-mass-driven (e.g. thermal expansion?)

- freshwater loss from land was found to be at present the lead driver of the mass-driven change as per the paper (over what timeframe?)

- title says it's the primary driver for GMSL change overall, which this alone doesn't support (i.e. the title is a lie)

- @ornel (the person posting) points to another study that claims mass-driven change is the leading change, hence the title [0, this doesn't pass my smell test but i see the logic]

- you point out that that's glossing over that that other study is counting from 1900, but if one shrunk the evaluation window, the non-mass-driven causes would be the drivers now [1, this doesn't pass my smell test either, but i see the logic here as well]

The latter point then begs the question though, what is the time window in this case then, and how stable that result is? What would be an "appropriate" time window to choose, and how would one derive that?

Regarding my non-passing smell tests, imagine the following scenario for some event:

- category A: 51% of the total

- cause A1: 26% of the total

- cause A2: 25% of the total

- category B: 49% of the total

- cause B1: 27% of the total

- cause B2: 22% of the total

In this case, category A will be the lead contributor, but individually none of its contributing causes will be, addressing [0]. The causes will be ordered like so instead: B1 > A1 > A2 > B2. More elaborate variations are possible of course. For [1], you can imagine the same scenario just in reverse.

Did I get all this right?

garrettdreyfus · 22 days ago
Hi,

I appreciate the effort in your comment. I think upon further reflection my simpler objection is calling freshwater loss the main driver of sea level rise when the journal article and news article don’t. Also I would note this is only one study.

garrettdreyfus commented on Shrinking freshwater availability increasing land contribution to sea level rise   news.asu.edu/20250725-env... · Posted by u/ornel
garrettdreyfus · 22 days ago
garrettdreyfus · 22 days ago
Although to your point it does vary alot over different windows of time.
garrettdreyfus commented on Shrinking freshwater availability increasing land contribution to sea level rise   news.asu.edu/20250725-env... · Posted by u/ornel
garrettdreyfus · 22 days ago
The study you cite is talking about sea level rise since 1900 which is a very different story.

The IPCC section “9.6.1.1 Global Mean Sea Level Change Budget in the Pre-satellite Era” says Since SROCC, a new ocean heat content reconstruction (Section 2.3.3.1; Zanna et al., 2019) has allowed global thermosteric sea level change to be estimated over the 20th century. As a result, the sea level budget for the 20th century can now be assessed for the first time. For the periods 1901–1990 and 1901–2018, the assessed very likely range for the sum of components is found to be consistent with the assessed very likely range of observed GMSL change (medium confidence), in agreement with Frederikse et al. (2020b; Table 9.5). This represents a major step forward in the understanding of observed GMSL change over the 20th century, which is dominated by glacier (52%) and Greenland Ice Sheet mass loss (29%) and the effect of ocean thermal expansion (32%), with a negative contribution from the LWS change (–14%). While the combined mass loss for Greenland and glaciers is consistent with SROCC, updates in the underlying datasets lead to differences in partitioning of the mass loss.”

Edit: by a different story I mean a different story from what is the leading driver of sea level rise. Sea level rise from ice melt was larger since 1900 because sea level rise in general was less fast back then and global mean temperature rise was much smaller so thermosteric sea level rise played less of a role. Thermosteric sea level rise is larger than ground water factors, both will be eclipsed by ice melt in the upcoming century.

I would note the authors pointedly do not call it the leading driver of sea level rise.

garrettdreyfus commented on Shrinking freshwater availability increasing land contribution to sea level rise   news.asu.edu/20250725-env... · Posted by u/ornel
ornel · 22 days ago
Quote from the paper: "the continents are now the leading contributor (44%) to mass-driven GMSL rise". As regards to non-mass-driven rise, another article[0] states, "Ice-mass loss—predominantly from glaciers—has caused twice as much sea-level rise since 1900 as has thermal expansion". I think the findings about sea level rise are as interesting as the ones about fresh water disappearance.

[0] https://www.nature.com/articles/s41586-020-2591-3

garrettdreyfus · 22 days ago
The study you cite is talking about sea level rise since 1900 which is a very different story.

The IPCC section “9.6.1.1 Global Mean Sea Level Change Budget in the Pre-satellite Era” says Since SROCC, a new ocean heat content reconstruction (Section 2.3.3.1; Zanna et al., 2019) has allowed global thermosteric sea level change to be estimated over the 20th century. As a result, the sea level budget for the 20th century can now be assessed for the first time. For the periods 1901–1990 and 1901–2018, the assessed very likely range for the sum of components is found to be consistent with the assessed very likely range of observed GMSL change (medium confidence), in agreement with Frederikse et al. (2020b; Table 9.5). This represents a major step forward in the understanding of observed GMSL change over the 20th century, which is dominated by glacier (52%) and Greenland Ice Sheet mass loss (29%) and the effect of ocean thermal expansion (32%), with a negative contribution from the LWS change (–14%). While the combined mass loss for Greenland and glaciers is consistent with SROCC, updates in the underlying datasets lead to differences in partitioning of the mass loss.”

Edit: by a different story I mean a different story from what is the leading driver of sea level rise. Sea level rise from ice melt was larger since 1900 because sea level rise in general was less fast back then and global mean temperature rise was much smaller so thermosteric sea level rise played less of a role. Thermosteric sea level rise is larger than ground water factors, both will be eclipsed by ice melt in the upcoming century.

I would note the authors pointedly do not call it the leading driver of sea level rise.

garrettdreyfus commented on Shrinking freshwater availability increasing land contribution to sea level rise   news.asu.edu/20250725-env... · Posted by u/ornel
srameshc · 22 days ago
> New findings from studying over two decades of satellite observations reveal that the Earth’s continents have experienced unprecedented freshwater loss since 2002, driven by climate change, unsustainable groundwater use and extreme droughts.

The title captures the crux of the story

garrettdreyfus · 22 days ago
Sorry I am referring to HN submission title not the article title
garrettdreyfus commented on Shrinking freshwater availability increasing land contribution to sea level rise   news.asu.edu/20250725-env... · Posted by u/ornel
garrettdreyfus · 22 days ago
I’m not sure this title is completely correct

“The researchers identified the type of water loss on land, and for the first time, found that 68% came from groundwater alone — contributing more to sea level rise than glaciers and ice caps on land.”

They are saying the leading loss of water loss is from ground water. The largest contributor to sea level rise I would guess is still thermosteric sea level rise due to the ocean becoming warmer and less dense

See ipcc https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-9/

9.6.1 Global and Regional Sea Level Change in the Instrumental Era

In particular, Cross-Chapter 9.1, Figure 1 | Global Energy Inventory and Sea Level Budget. Panel b

EDIT: @dang could the submission title be changed to the article or journal article title?

“New global study shows freshwater is disappearing at alarming rates”

Or

“Unprecedented continental drying, shrinking freshwater availability, and increasing land contributions to sea level rise”

garrettdreyfus · 22 days ago
My reading of Figure 6 https://www.science.org/doi/10.1126/sciadv.adx0298 suggests that this study still has thermosteric effects making up the majority of sea level rise.

I also highly recommend reading up on the GRACE satellite used in this study it is amazing https://gracefo.jpl.nasa.gov/resources/50/how-grace-fo-measu...

garrettdreyfus commented on Shrinking freshwater availability increasing land contribution to sea level rise   news.asu.edu/20250725-env... · Posted by u/ornel
garrettdreyfus · 22 days ago
I’m not sure this title is completely correct

“The researchers identified the type of water loss on land, and for the first time, found that 68% came from groundwater alone — contributing more to sea level rise than glaciers and ice caps on land.”

They are saying the leading loss of water loss is from ground water. The largest contributor to sea level rise I would guess is still thermosteric sea level rise due to the ocean becoming warmer and less dense

See ipcc https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-9/

9.6.1 Global and Regional Sea Level Change in the Instrumental Era

In particular, Cross-Chapter 9.1, Figure 1 | Global Energy Inventory and Sea Level Budget. Panel b

EDIT: @dang could the submission title be changed to the article or journal article title?

“New global study shows freshwater is disappearing at alarming rates”

Or

“Unprecedented continental drying, shrinking freshwater availability, and increasing land contributions to sea level rise”

garrettdreyfus commented on Loss of key US satellite data could send hurricane forecasting back 'decades'   theguardian.com/us-news/2... · Posted by u/trauco
e44858 · 2 months ago
This is likely because the DMSP satellites are outdated: "In 2015, Congress voted to terminate the DMSP program and to scrap the DMSP 5D-3/F20 satellite, ordering the Air Force to move on to a next-generation system." https://en.wikipedia.org/wiki/Defense_Meteorological_Satelli...

The GOES-R satellites seem to have equal or better resolution: https://journals.ametsoc.org/view/journals/atot/4/4/1520-042...https://en.wikipedia.org/wiki/GOES-16

DMSP resolves to 600m, while GOES-R resolves to 500m (don't confuse it with the older GOES satellites mentioned in the article).

u/garrettdreyfus

KarmaCake day192October 3, 2013View Original