Evaluation of the accuracy of an offline seasonallyvarying matrix transport model for simulating ideal age
NewtonKrylov solvers for ocean tracers have the potential to greatly decrease the computational costs of spinning up deepocean tracers, which can take several thousand model years to reach equilibrium with surface processes. One version of the algorithm uses offline tracer transport matrices to simulate an annual cycle of tracer concentrations and applies Newton’s method to find concentrations that are periodic in time. Here we present the impact of timeaveraging the transport matrices on the equilibrium values of an idealage tracer. We compared annuallyaveraged, monthlyaveraged, and 5dayaveraged transport matrices to an online simulation using the ocean component of the Community Earth System Model (CESM) with a nominal horizontal resolution of 1° × 1° and 60 vertical levels. We found that increasing the time resolution of the offline transport model reduced a low age bias from 12% for the annuallyaveraged transport matrices, to 4% for the monthlyaveraged transport matrices, and to less than 2% for the transport matrices constructed from 5day averages. The largest differences were in areas with strong seasonal changes in the circulation, such as the Northern Indian Ocean. As a result, for many applications the relatively small bias obtained using the offline model makes the offline approach attractive becausemore »
 Authors:

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 Univ. of California, Irvine, CA (United States)
 National Center for Atmospheric Research, Boulder, CO (United States)
 Sandia National Lab. (SNLNM), Albuquerque, NM (United States)
 Publication Date:
 Report Number(s):
 SAND20166880J
Journal ID: ISSN 14635003; PII: S1463500316300750
 Grant/Contract Number:
 AC0494AL85000
 Type:
 Accepted Manuscript
 Journal Name:
 Ocean Modelling
 Additional Journal Information:
 Journal Volume: 105; Journal Issue: C; Journal ID: ISSN 14635003
 Publisher:
 Elsevier
 Research Org:
 Sandia National Lab. (SNLNM), Albuquerque, NM (United States)
 Sponsoring Org:
 USDOE National Nuclear Security Administration (NNSA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 58 GEOSCIENCES; 54 ENVIRONMENTAL SCIENCES; implicit solver; ideal age; Newton–Krylov; offline; transport matrix; global ocean modeling
 OSTI Identifier:
 1275512
 Alternate Identifier(s):
 OSTI ID: 1398012
Bardin, Ann, Primeau, Francois, Lindsay, Keith, and Bradley, Andrew. Evaluation of the accuracy of an offline seasonallyvarying matrix transport model for simulating ideal age. United States: N. p.,
Web. doi:10.1016/j.ocemod.2016.07.003.
Bardin, Ann, Primeau, Francois, Lindsay, Keith, & Bradley, Andrew. Evaluation of the accuracy of an offline seasonallyvarying matrix transport model for simulating ideal age. United States. doi:10.1016/j.ocemod.2016.07.003.
Bardin, Ann, Primeau, Francois, Lindsay, Keith, and Bradley, Andrew. 2016.
"Evaluation of the accuracy of an offline seasonallyvarying matrix transport model for simulating ideal age". United States.
doi:10.1016/j.ocemod.2016.07.003. https://www.osti.gov/servlets/purl/1275512.
@article{osti_1275512,
title = {Evaluation of the accuracy of an offline seasonallyvarying matrix transport model for simulating ideal age},
author = {Bardin, Ann and Primeau, Francois and Lindsay, Keith and Bradley, Andrew},
abstractNote = {NewtonKrylov solvers for ocean tracers have the potential to greatly decrease the computational costs of spinning up deepocean tracers, which can take several thousand model years to reach equilibrium with surface processes. One version of the algorithm uses offline tracer transport matrices to simulate an annual cycle of tracer concentrations and applies Newton’s method to find concentrations that are periodic in time. Here we present the impact of timeaveraging the transport matrices on the equilibrium values of an idealage tracer. We compared annuallyaveraged, monthlyaveraged, and 5dayaveraged transport matrices to an online simulation using the ocean component of the Community Earth System Model (CESM) with a nominal horizontal resolution of 1° × 1° and 60 vertical levels. We found that increasing the time resolution of the offline transport model reduced a low age bias from 12% for the annuallyaveraged transport matrices, to 4% for the monthlyaveraged transport matrices, and to less than 2% for the transport matrices constructed from 5day averages. The largest differences were in areas with strong seasonal changes in the circulation, such as the Northern Indian Ocean. As a result, for many applications the relatively small bias obtained using the offline model makes the offline approach attractive because it uses significantly less computer resources and is simpler to set up and run.},
doi = {10.1016/j.ocemod.2016.07.003},
journal = {Ocean Modelling},
number = C,
volume = 105,
place = {United States},
year = {2016},
month = {7}
}