Current Climate Model Simulations Significantly Overestimate Future Sea-Level Rise

Wrong Sea Level Concept

The melting rate of the Antarctic ice sheet is mainly controlled by the increase of ocean temperatures surrounding Antarctica. Using a new, higher-resolution climate model simulation, scientists from Utrecht University found a much slower ocean temperature increase compared to current simulations with a coarser resolution. Consequently, the projected sea-level rise in 100 years is about 25% lower than expected from the current simulations. These results were published in the journal Science Advances.

Estimates for future sea-level rise are based on a large ensemble of climate model simulations. The output from these simulations helps to understand future climate change and its effects on the sea level. Climate researchers continually aim to improve these models, for example by using a much higher spatial resolution that takes more details into account. “High-resolution simulations can determine the ocean circulation much more accurately,” says Prof. Henk Dijkstra. Together with his PhD candidate René van Westen, he has been studying ocean currents in high-resolution climate model simulations over the past few years.

Ocean eddies

The new high-resolution model takes into account ocean eddy processes. An eddy is a large (10 – 200 km) swirling and turbulent feature in the ocean circulation, which contributes to the transport of heat and salt. Adding ocean eddies into the simulation leads to a more realistic representation of the ocean temperatures surrounding Antarctica, which is key for determining the mass loss of the Antarctic ice sheet. “The Antarctic ice sheet is surrounded by ice shelves which reduce the flow of land ice into the ocean,” Van Westen explains. “Higher ocean temperatures around Antarctica increase the melting of these ice shelves, resulting in an acceleration of land ice into the ocean and consequently leading to more sea-level rise.”

The current climate model simulations, which do not take ocean eddies into account, project that the ocean temperatures around Antarctica are increasing under climate change. The new high-resolution simulation shows quite different behavior and some regions near Antarctica even cool under climate change. “These regions appear to be more resilient under climate change,” says Van Westen. Dijkstra adds: “One obtains a very different temperature response due to ocean-eddy effects.”  

Supercomputer

The new high-resolution model projects a smaller mass loss as a result of ice-shelf melt: only one third compared to current climate models. This reduces the projected global sea-level rise by 25% in the upcoming 100 years, Van Westen mentions. “Although sea levels will continue to rise, this is good news for low-lying regions. In our simulation, ocean eddies play a crucial role in sea-level projections, showing that these small-scale ocean features can have a global effect.” It took the team about one year to complete the high-resolution model simulation on the national supercomputer at SURFsara in Amsterdam. Dijkstra: “These high-resolution models require an immense amount of computation, but are valuable as they reveal smaller-scale physical processes which should be taken into account when studying climate change.”

Reference: “Ocean eddies strongly affect global mean sea-level projections” by René M. van Westen and Henk A. Dijkstra, 9 April 2021, Science Advances.
DOI: 10.1126/sciadv.abf1674

8 Comments on "Current Climate Model Simulations Significantly Overestimate Future Sea-Level Rise"

  1. I’ll wait a year or two until several more of the more granular models, using a diversity of computing assets, bring in their results.

  2. Clyde Spencer | April 11, 2021 at 3:47 pm | Reply

    The author of the study makes the oft repeated claim: “The Antarctic ice sheet is surrounded by ice shelves which reduce the flow of land ice into the ocean,… Higher ocean temperatures around Antarctica increase the melting of these ice shelves, resulting in an acceleration of land ice into the ocean and consequently leading to more sea-level rise.”

    Nowhere do I see even a citation in the actual linked article supporting the claim. It has become like an urban legend!

    The glaciers entering the ocean have a small, but measurable, velocity that imparts momentum to the ice mass. Pack ice that freezes onto the leading edge of the glacial ice acquires the same momentum. Any friction with the water itself is negligible compared to friction with the bedrock upslope from the shoreline. In most cases, it appears that the grounding lines are unconsolidated recessional moraines that offer little resistance either, particularly since the ice, while not actually floating, is buoyed up by the ice, reducing the pressure on the grounding line compared to what the ice experiences above the shoreline. Thus, the primary driver to the movement of the AIS is the friction with the ground, which is controlled by the slope of the bedrock and the thickness of the ice. If the ground friction gets high enough, the ice can and will shear plastically over rough topography.

    The pack or shelf ice frequently calves huge icebergs along tensional cracks. If it was acting as a buttress, it would be under compressional stress, and not develop tensional cracks.

    Claims are being made for which the facts are not in evidence. It is often the unstated, and unexamined, assumptions that gets one into trouble!

  3. Larry Wilson | April 11, 2021 at 4:31 pm | Reply

    If this report turns out to be case, it will take 133 years rather than 100 years for sea level to reach the level predicted by the coarse modeling. While that would be welcome and give us an extra 33 years to prepare, it’s not a game changer by any means.

  4. Michael R Lawson | April 11, 2021 at 7:12 pm | Reply

    so a rise of ~34cm which is ~ 13 inches…in 80 years….lol

  5. And the report of two days earlier (Apr 9th), of the actual measurement of sea water temperatures under the ice (measurements – not theoretical opinions!), show just the opposite. That the ice is melting much faster than previously estimated. [Link in side-bar]

  6. kelley edwin sims | April 12, 2021 at 4:21 am | Reply

    10c by 2050

    said it for 20 years now. our children will inherit a wasteland we destroyed.

    novaya zemlaya is a desert with polar bears already, siberia already melted. and the climate models never take into account the bacteria overgrowth in the arctic ocean (bacteria produce heat as a byproduct of growth and reproduction).

    mean while the thermocline temperature variation around greenland has no temperature difference for a 1000 meters below sea level….

    but oh, climate change wont be that bad.

    its been building for 200 years. people act like humans are smart enough to stop it

    10c by 2050

  7. Can anyone out there please tell me if calculations for sea level rise take into account the fact that when areas do become flooded and stay flooded this effectively lowers sea levels. I ask this because I live in an area on the east coast that is below sea level and protected by sand dunes but when the dunes are eventually breached the sea will reach the wolds and this is a large area and surely this process will be repeated in many parts of the world so do the calculations take this into account?

  8. Peter Marshall | April 13, 2021 at 3:53 pm | Reply

    So the 2 percent case 79 years out combined with bad models produces hysteria. The models are not that reliable. The IPCC co2 absorbsion rate is off by 10x! Let us examine the data. It was fudged.

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