The Transient Sea Level Response to External Forcing in CMIP6 Models

Abstract Earth is warming and sea levels are rising as land‐based ice is lost to melt, and oceans expand due to accumulation of heat. The pace of ice loss and steric expansion is linked to the intensity of warming. How much faster sea level will rise as climate warms is, however, highly uncertain an...

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Bibliographic Details
Published in:Earth's Future
Main Authors: Aslak Grinsted, Jonathan Bamber, Rory Bingham, Sammie Buzzard, Isabel Nias, Kelvin Ng, Jennifer Weeks
Format: Article in Journal/Newspaper
Language:English
Published: Wiley 2022
Subjects:
geo
Online Access:https://doi.org/10.1029/2022EF002696
https://doaj.org/article/d0ed742ab4ab4edda27877b4cdd6b180
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Summary:Abstract Earth is warming and sea levels are rising as land‐based ice is lost to melt, and oceans expand due to accumulation of heat. The pace of ice loss and steric expansion is linked to the intensity of warming. How much faster sea level will rise as climate warms is, however, highly uncertain and difficult to model. Here, we quantify the transient sea level sensitivity of the sea level budget in both models and observations. Models show little change in sensitivity to warming between the first and second half of the twenty‐first century for most contributors. The exception is glaciers and ice caps (GIC) that have a greater sensitivity pre‐2050 (2.8 ± 0.4 mm/yr/K) compared to later (0.7 ± 0.1 mm/yr/K). We attribute this change to the short response time of glaciers and their changing area over time. Model sensitivities of steric expansion (1.5 ± 0.2 mm/yr/K), and Greenland Ice Sheet mass loss (0.8 ± 0.2 mm/yr/K) are greater than, but still compatible with, corresponding estimates from historical data (1.4 ± 0.5 and 0.4 ± 0.2 mm/yr/K). Antarctic Ice Sheet (AIS) models tends to show lower rates of sea level rise (SLR) with warming (−0.0 ± 0.3 mm/yr/K) in contrast to historical estimates (0.4 ± 0.2 mm/yr/K). This apparent low bias in AIS sensitivity is only partly able to account for a similar low bias identified in the sensitivity of global mean sea level excluding GIC (3.1 ± 0.4 vs. 2.3 ± 0.4 mm/yr/K). The balance temperature, where SLR is zero, lies close to the pre‐industrial value, implying that SLR can only be mitigated by substantial global cooling.