Are ocean bottom pressure variations from CMIP6 HighResMIP useful for future gravity mission simulations?

Ocean bottom pressure (p_b) variations from high-resolution climate model simulations under
the CMIP6 (Coupled Model Intercomparison Project Phase 6) HighResMIP protocol are a
potentially useful input for future gravity mission simulation studies, but the overall signal content
and accuracy of these p_b estimates has hitherto not been assessed. Here we compute monthly
p_b fields from five CMIP6 HighResMIP models at1/4° grid spacing over both historical and future
time spans and compare these data, in terms of temporal variance, against observation-based
p_b estimates from a 1/4° downscaled GRACE (Gravity Recovery and Climate Experiment)
product and 23 bottom pressure recorders, mostly in the Pacific. The model results are
qualitatively and quantitatively similar to the GRACE-based p_b estimates, featuring—aside
from eddy imprints—elevated amplitudes on continental shelves and in major abyssal plains of
the Southern Ocean. Modeled p_b variance in these regions is ~10–80% higher and thus
overestimated relative to GRACE, whereas underestimation (~30%) prevails in more quiescent
deep-ocean regions. Comparisons with the bottom pressure recorders tend to confirm this
picture. We also form variance ratios of detrended p_b signals over 2030–2049 under a high-
emission scenario relative to a baseline period of 1980–1999 for three selected models and find
evidence for a statistically significant strengthening of future p_b variance by 30–50% across
the Arctic and in eddy-rich regions of the South Atlantic. Together, our results suggest that p_b
estimates from CMIP6 HighResMIP models can inform satellite gravimetry simulations and that
climate-driven changes in p_b variance should be considered in such efforts.