Oceanography | Vol. 38, No. 3
10
FUTURE OGCM PRIORITIES
Returning to Figure 1, notice that the LLC4320 simulation is
already a decade old. Moore’s law has continued in the years since
NASA computed LLC4320, and the time is ripe to make a new
benchmark cutting-edge calculation. Extrapolating the OGCM
red line in Figure 1 suggests that such a new simulation could
have 3 × 109 horizontal grid cells, which corresponds to a horizon-
tal grid scale of 350 m. This resolution captures part of the unex-
plored regime of submesoscale dynamics in which rotational, iner-
tial, and buoyancy effects are all of similar importance (Taylor and
Thompson, 2023), and which is very hard to observe with current
oceanographic instruments.
Alternatively, the extra computational power could be spent
on other priorities. For example, the simulation could be run for
longer than one year at the same resolution as LLC4320. Or the
initial condition could be improved to avoid transient adjustments
during the simulation. The question is, what are the most import-
ant priorities and, in particular, how should the extra computa-
tional power be spent?
This question was asked during a town hall meeting at the
2024 Ocean Sciences Meeting. Participants in the town hall
responded to an online survey that asked them to rank 11 differ-
ent priorities for designing the next cutting-edge global bench-
mark OGCM simulation. Participants could also write in their
own priorities. Figure 4 shows the results of the survey, summa-
rizing the opinions of 44 respondents (the survey is still open—
take the survey).
The survey results show no consensus for future bench-
mark OGCM solutions because all the priorities were ranked as
important by some respondents and as unimportant by others.
Nevertheless, preferences are clear overall. The most highly
ranked priorities include longer run time and better horizon-
tal and vertical resolution. These priorities are relatively easy to
implement because they require little OGCM code development
and little pre-computation before the main OGCM code is run.
Better model spin-up/initial conditions and better air-sea forc-
ing are also highly ranked. These priorities are harder to imple-
ment because they involve improvements (which need to be
precisely defined) to input data from other large, complex mod-
eling systems. The four middle-ranked priorities are: better con-
straints to observations, better model parametrizations, better
model topography, and better mean circulation and stratifica-
tion. These are desirable scientific goals that are easy to state but
hard to achieve. One reason is that they involve detailed tuning of
OGCM parameters and input data, or improvements to OGCM
software. Another reason is that these priorities are interrelated
because, for example, improving the mean circulation probably
requires better parametrizations and topography, which will inev-
itably improve agreement with observations. Two priorities were
ranked as unimportant overall, namely an ensemble of LLC4320
runs (easy to implement) and better diversity in model code
(relatively easy to implement using existing OGCM systems).
Other priorities listed by a few respondents included adding
biogeochemistry, better documentation, and better comparison
with observations.
OUTLOOK
Given the ongoing advances in computational hardware, software,
and infrastructure, the time is ripe for a new cutting-edge OGCM
solution (or more than one) to be computed. Efforts like LLC4320
and the Poseidon Project require significant resources and there-
fore need broad support from academia, industry, funding agen-
cies, and non-professional oceanographers. To date, these efforts
have been supported by government agencies and private founda-
tions with standalone projects every few years. The need to sustain
open shared cyberinfrastructure like SciServer and digital twins
like LLC4320 is widely recognized (Barker et al., 2019; Grossman,
2023; Le Moigne et al., 2023; NASEM, 2024). The future sources of
support and the pathway for migrating from research project fund-
ing to community infrastructure funding are uncertain, however.
One notable example of a stable, long-term, cloud-based data
analysis environment for ocean sciences is the Mercator Ocean
International and Copernicus Marine Service resource, funded
by the European Commission. It provides real-time global ocean
hindcasts, analyses, and forecasts using ocean circulation models,
in situ and remote observations, and data assimilation (although
not presently at the LLC4320 horizontal resolution). Their focus is
on operational oceanography and the state of the ocean for diverse
stakeholders (von Schuckmann et al., 2024). Apart from aca-
demic users, people have applied the Copernicus Marine Service
PRIORITIES FOR FUTURE GLOBAL
BENCHMARK OGCM SIMULATIONS
FIGURE 4. Results from a 2024 Ocean Sciences Meeting survey on prior-
ities for the next benchmark global OGCM simulation. Forty-four respon-
dents ranked the priorities on the y-axis on a scale of 1 to 12 (1 is the top pri-
ority). The median value is shown with the dotted circle, the 25th and 75th
percentiles are shown with the thick bar, and the thin bars indicate maximum
and minimum values. “Other(s) (write in)” priorities included adding biogeo-
chemistry, better documentation and tutorials, and better evaluation with
observations. Take the survey.