Human depletion of underground reservoirs has shifted the global distribution of water so much that the North Pole has drifted by more more than 4 centimetres per year.

Not alarmist, just cool. When I was in grad school we studied we used dInSAR to study groundwater pumping related subsidence. It makes perfect sense that there would be mass redistribution.

  • TroyOPMEnglish
    1·
    1 year ago

    Shit, I just realized I replied to this comment thinking it was in another thread, about sand mining and subsidence.

    Okay, fixing it.

    (1) water takes a long time to enter reservoirs naturally. If it’s drawn faster than it trickles back in, it tends to be lost to evaporation or surface run-off. So it ends up in the ocean or the atmosphere. Thus, mass redistribution.
    (2) Yes, for highly irrigated places, like the US southwest, groundwater levels are very noticeably impacted. They can’t sustain that level of irrigation forever.
    (3) Generally speaking, this time of groundwater use doesn’t create voids, except microscopically. Those voids tend to be compressed as the surface weight presses down. Whereas previously they were filled with water, now they have air or nothing, and the voids shrink as the ground compresses. It’s usually on the scale of millimetres and can be measured by dInSAR.

    • glandridEnglish
      2·
      1 year ago

      Thanks for your detailed response, Troy! Not a climate change denier, but I wonder if it all of that extra water/moisture in the atmosphere has had any impact on the temperature or weather.

      • TroyOPMEnglish
        2·
        1 year ago

        It doesn’t stay in the atmosphere for long – it’ll rain somewhere else and run into the ocean.

        Water is an interesting greenhouse gas. When it is in the atmosphere as vapour, it is a very potent greenhouse gas. But the atmosphere has a load bearing limit – how much water can it hold before clouds form. And clouds, ironically, reflect sunlight away from the earth and back into space (they are white, after all…). So in the end, water in the atmosphere will reach an equilibrium that is related to the temperature of the atmosphere. The hotter the atmosphere, the more vapour it can hold before turning into clouds.

        Largely though, any additional water vapour in the air due to irrigation is trivial compared to the water that evaporates from the ocean surfaces. And global warming is heating the oceans, causing more evaporation, which is a feedback loop. Particularly in the arctic, where ice cover used to reflect sunlight back into space, open water is now absorbing sunlight and reinforcing the feedback loop.

        Irrigation water evaporation is largely a short term climate issue, but locally, once the water runs out, it will be a major problem – fields will turn back into deserts unless water is shipped in.