4.5mm a year doesn’t sound like much, but that’s far from the full story. Regional variations, water sources, gravity, currents, rebound and surges combine to make it a serious accelerating threat.
I would have thought the increase in water vapor as a green house gas would increase the overall heat content and hence its impact on melting the glacial mass and ice sheets. As there is a reduction in precipitating nuclei as a result of land use changes then this mass will stay as vapor longer before condensation into cloud.
Another note I referred to before is the percentage of coastline which has built an equilibrium balance of slope to erosion of this slope as most shorelines are either rock overlain with clay or just clay of varying rigidity both of which are susceptible to undercutting and destabilizing the clay topsoil's of the whole slope. I saw the start of this undercutting in New Zealand and the turbidity effects on the fragile estuarial ecosystems. Such ecosystems when in balance can handle the turbidity in sporadic events but as sea levels rise this will not be storm related but happen on any windy day.
Thermocline mixing for hurricane dampening has been studied in places like the gulf of Mexico using old oil rigs I assume but may be more necessary if our current projections are too optimistic.
Thanks Theodore, The erosion effect you describe is interesting. I knew sea level rise would increase erosion but didn't know about that undercutting mechanism.
Micheal asked whether the increase in atmospheric water vapour was counteracting the various melting effects. I found some numbers which suggested it was less than 2mm over 40 years.
The complexity of the various feedbacks and other activities, like the land use change you describe, are so very complex.
Clay seems to act in a similar way to a glacier when undercut. Each rain event leads to an expansion and the dry interval leads to contraction which creates cavities for water so the whole mass starts to move down hill and fractures at the bottom falling off in large boulder like chunks. I Started planting mangroves where I could even amongst the rocks just to reduce wave action.
Water vapor I would have thought being the most abundant GHG would have a big impact on global warming if it stayed in the vapor form for longer, but as you point out maybe the amount is too small to have a big impact even though water vapour has a specific heat capacity of 1.8 kJ/kgk almost double that of air. That said if it is lasting longer in the vapor form one would assume the increase would be accumulative on top of the 4.5% increase, expanding heat domes and increasing the VPD.
Interesting. The protection benefits of mangroves and giant kelp on wave action is very important.
Water vapour is certainly factored into the models in terms of their increase in GHG capability, but are not accumulative like CO2. I don't know whether the longer resident time in the air is factored in though.
My thoughts on resident time and lack of nucleation is that it adds to amplification and that the warm moist air mass would have higher levels of condensation directly with the ice mass instead of creating localized cloud and therefore melting and runoff.
This is a must-read article for those of us concerned with climate change. Very much appreciate the work that went into it.
Will warmer air leading to increased oceanic evaporation, resulting in more water vapor permanently in the atmosphere to any degree offset cryosphere melting inputs? I haven't run into any discussions of that nature.
Certainly the specific humidity of the atmosphere has gone up with temperature rise. In 1980 it was about 7.75g/kg at sea level and is now ~8.1g/kg on average globally. What that means in terms of total mass in the air I don't know, but it's about a 4.5% increase.
I did a quick search and found a source saying the water vapour in the air was equivalent to 38mm of sea level. So the increase since 1980 of 4.5% would be removing ~1.7mm of sea level rise. Not a massive help.
Not enough for sure. The sea level rise would be hardly slowed down
It's fascinating how all the feedback loops work. Greater warming increases evaporation leading to more water vapor in the atmosphere which leads to more cloud formation which increases albedo which lessens warming but then increases heat trapping! One can see the system’s tendencies to homeostasis slowly breaking down under the relentless accumulation of zettajoules of energy.
I would have thought the increase in water vapor as a green house gas would increase the overall heat content and hence its impact on melting the glacial mass and ice sheets. As there is a reduction in precipitating nuclei as a result of land use changes then this mass will stay as vapor longer before condensation into cloud.
Another note I referred to before is the percentage of coastline which has built an equilibrium balance of slope to erosion of this slope as most shorelines are either rock overlain with clay or just clay of varying rigidity both of which are susceptible to undercutting and destabilizing the clay topsoil's of the whole slope. I saw the start of this undercutting in New Zealand and the turbidity effects on the fragile estuarial ecosystems. Such ecosystems when in balance can handle the turbidity in sporadic events but as sea levels rise this will not be storm related but happen on any windy day.
Thermocline mixing for hurricane dampening has been studied in places like the gulf of Mexico using old oil rigs I assume but may be more necessary if our current projections are too optimistic.
Thanks again for such a thorough post.
Thanks Theodore, The erosion effect you describe is interesting. I knew sea level rise would increase erosion but didn't know about that undercutting mechanism.
Micheal asked whether the increase in atmospheric water vapour was counteracting the various melting effects. I found some numbers which suggested it was less than 2mm over 40 years.
The complexity of the various feedbacks and other activities, like the land use change you describe, are so very complex.
All the best.
Clay seems to act in a similar way to a glacier when undercut. Each rain event leads to an expansion and the dry interval leads to contraction which creates cavities for water so the whole mass starts to move down hill and fractures at the bottom falling off in large boulder like chunks. I Started planting mangroves where I could even amongst the rocks just to reduce wave action.
Water vapor I would have thought being the most abundant GHG would have a big impact on global warming if it stayed in the vapor form for longer, but as you point out maybe the amount is too small to have a big impact even though water vapour has a specific heat capacity of 1.8 kJ/kgk almost double that of air. That said if it is lasting longer in the vapor form one would assume the increase would be accumulative on top of the 4.5% increase, expanding heat domes and increasing the VPD.
Interesting. The protection benefits of mangroves and giant kelp on wave action is very important.
Water vapour is certainly factored into the models in terms of their increase in GHG capability, but are not accumulative like CO2. I don't know whether the longer resident time in the air is factored in though.
My thoughts on resident time and lack of nucleation is that it adds to amplification and that the warm moist air mass would have higher levels of condensation directly with the ice mass instead of creating localized cloud and therefore melting and runoff.
This is a must-read article for those of us concerned with climate change. Very much appreciate the work that went into it.
Will warmer air leading to increased oceanic evaporation, resulting in more water vapor permanently in the atmosphere to any degree offset cryosphere melting inputs? I haven't run into any discussions of that nature.
Great article!
Thanks, that's a great question.
Certainly the specific humidity of the atmosphere has gone up with temperature rise. In 1980 it was about 7.75g/kg at sea level and is now ~8.1g/kg on average globally. What that means in terms of total mass in the air I don't know, but it's about a 4.5% increase.
I did a quick search and found a source saying the water vapour in the air was equivalent to 38mm of sea level. So the increase since 1980 of 4.5% would be removing ~1.7mm of sea level rise. Not a massive help.
Not enough for sure. The sea level rise would be hardly slowed down
It's fascinating how all the feedback loops work. Greater warming increases evaporation leading to more water vapor in the atmosphere which leads to more cloud formation which increases albedo which lessens warming but then increases heat trapping! One can see the system’s tendencies to homeostasis slowly breaking down under the relentless accumulation of zettajoules of energy.
Absolutely, no wonder it's so hard to model accurately.