Low-Frequency Dynamic Ocean Response to Barometric-Pressure Loading

Piecuch, Christopher G.; Fukumori, Ichiro; Ponte, Rui M.; Schindelegger, Michael; Wang, Ou; Zhao, Mengnan

doi:10.1175/jpo-d-22-0090.1

Cited by 6 publications

(7 citation statements)

References 93 publications

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“…Similarly for cool anomalies and low DSL anomalies. A qualitative upper bound on the role of this process in driving DSL on the NWES can be obtained by decomposing DSL, η , into a (dynamic) manometric component, η m (Piecuch et al., 2022), and a steric component, η s , such that

\eta ={\eta }_{m}+{\eta }_{s},

with

{\eta }_{m}=\frac{1}{g{\rho }_{s}}{p}_{b},

{\eta }_{s}=-\frac{1}{{\rho }_{s}}\int \nolimits_{-H}^{0}\rho \,dz.

…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Using Shelf‐Edge Transport Composition and Sensitivity Experiments to Understand Processes Driving Sea Level on the Northwest European Shelf

Wise,

Calafat,

Hughes

et al. 2024

JGR Oceans

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Variability in ocean currents, temperature and salinity drive dynamic sea level (DSL) variability on the Northwest European Shelf (NWES). It is dominated by mass variations, with steric signals relatively small. A mechanistic explanation of how ocean dynamics relates to the mass component of NWES sea level variability is required. We use regional ocean model experiments to isolate sources of variability and then investigate the effect on monthly to‐interannual DSL variability together with the simulated momentum budgets along the shelfbreak. Regional (local) wind and non‐regional (remote) forcing are important on the NWES. For the local wind forcing, the net mass flux onto the shelf, which drives a shelf‐mean mode of DSL variability, results from a combination of surface Ekman, bottom Ekman and geostrophic flows and explains 73% of the variance in transport across the shelf‐edge. The geostrophic flow is closely related to wind stress with a flow about half that of surface Ekman transport but in the opposite direction. For the remotely forced mass‐flux across the shelf‐edge, the geostrophic component explains 62% of the variance and bottom friction plays an important indirect role. The remotely forced variability, while relatively spatially uniform, is more important for explaining DSL variance over the western NWES. This mode of variability is sensitive to signals propagating northward via a thin strip of the southern boundary near the Portuguese coast, consistent with coastal trapped wave signals. It also appears to drive steric height in the Bay of Biscay, which is related to DSL on the shelf.

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\eta ={\eta }_{m}+{\eta }_{s},

with

{\eta }_{m}=\frac{1}{g{\rho }_{s}}{p}_{b},

{\eta }_{s}=-\frac{1}{{\rho }_{s}}\int \nolimits_{-H}^{0}\rho \,dz.

…”

Section: Resultsmentioning

confidence: 99%

“…Similarly for cool anomalies and low DSL anomalies. A qualitative upper bound on the role of this process in driving DSL on the NWES can be obtained by decomposing DSL, η, into a (dynamic) manometric component, η m (Piecuch et al, 2022), and a steric component, η s , such that…”

Section: Local Wind Forcingmentioning

confidence: 99%

Using Shelf‐Edge Transport Composition and Sensitivity Experiments to Understand Processes Driving Sea Level on the Northwest European Shelf

Wise,

Calafat,

Hughes

et al. 2024

JGR Oceans

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show abstract

“…We especially propose to consider the dynamic ocean response to atmospheric pressure loading, which plays an important role in forcing rapid (sub‐weekly) rotation signals (Ponte & Ali, 2002). To some extent, it also acts on monthly to interannual time scales, at odds with a perfect IB behavior (Piecuch et al., 2022). Following the example of ECCOv4, it should be relatively straightforward for ocean reanalyses to assimilate monthly GRACE gravity field solutions as bottom pressure observations.…”

Section: Discussionmentioning

confidence: 99%

“…From the ΔΛ values, we remove tidal contributions at 80 spectral lines using the model by Ray and Erofeeva (2014). Similarly, long-period tidal effects in polar motion are accounted through the conventional model (Petit & Luzum, 2010), with the fortnightly component replaced by the Mf solution of Ray and Egbert (2012).…”

Section: Ancillary Data Setsmentioning

confidence: 99%

Are Ocean Reanalyses Useful for Earth Rotation Research?

Börger

Schindelegger

Dobslaw

et al. 2023

Earth and Space Science

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Oceanic circulation and mass‐field variability play important roles in exciting Earth's wobbles and length‐of‐day changes (ΔΛ), on time scales from days to several years. Modern descriptions of these effects employ oceanic angular momentum (OAM) series from numerical forward models or ocean state estimates, but nothing is known about how ocean reanalyses with sequential data assimilation (DA) would fare in that context. Here, we compute daily OAM series from three 1/4° global ocean reanalyses that are based on the same hydrodynamic core and input data (e.g., altimetry, Argo) but different DA schemes. Comparisons are carried out (a) among the reanalyses, (b) with an established ocean state estimate, and (c) with Earth rotation data, all focusing on the period 2006–2015. The reanalyses generally provide credible OAM estimates across a range of frequencies, although differences in amplitude spectra indicate a sensitivity to the adopted DA scheme. For periods less than 120 days, the reanalysis‐based OAM series explain ∼40%–50% and ∼30%–40% of the atmosphere‐corrected equatorial and axial geodetic excitation, similar to what is achieved with the state estimate. We find mixed performance of the reanalyses in seasonal excitation budgets, with some questionable mean ocean mass changes affecting the annual cycle in ΔΛ. Modeled excitations at interannual frequencies are more uncertain compared to OAM series from the state estimate and show hints of DA artifacts in one case. If users are to choose any of the tested reanalyses for rotation research, our study points to the Ocean Reanalysis System 5 as the most sensible choice.

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Section: Ancillary Data Setsmentioning

confidence: 99%

Are ocean reanalyses useful for Earth rotation research?

Börger

Schindelegger

2022

Preprint

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Oceanic circulation and mass-field variability play important roles in exciting Earth&#8217;s wobbles and changes in length-of-day (&#916;LOD), on time scales from days to several years. Quantifying these effects require estimates of ocean angular momentum (OAM), which are typically drawn from numerical forward models or coarse-resolution ocean state estimates. A little-tested alternative in this regard is the emerging suite of ocean reanalyses, operating at eddy-permitting horizontal resolution (1/4&#176;) and with sequential data assimilation (DA) schemes. Here, we compute geophysical excitation series from three identically configured global ocean reanalyses that are based on the same hydrodynamic core and input data (e.g., altimetry, Argo, sea surface temperature) but different DA schemes. The resulting OAM time series are compared both with each other and with atmosphere-corrected geodetic excitation from 2007 to 2011. For periods less than 120 days, the reanalyses series typically explain 40&#8211;50% of the residual observed polar motion excitation, somewhat less than a widely used ocean state estimate. By contrast, the reanalyses&#8217; skill in accounting for oceanic signals in &#916;LOD is more varied, particularly when seasonal and longer time scales are included in the comparison. This result points to a misclosure of the global mass balance constraint among atmosphere, ocean, and terrestrial hydrology, in part depending on whether or not a specific reanalysis considers the discharge of continental freshwater into the ocean. Together, our analyses provide insight into the kinematic consistency of newly available ocean reanalyses and give a quantitative understanding of the influence of different DA schemes on OAM estimates.

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Low-Frequency Dynamic Ocean Response to Barometric-Pressure Loading

Cited by 6 publications

References 93 publications

Using Shelf‐Edge Transport Composition and Sensitivity Experiments to Understand Processes Driving Sea Level on the Northwest European Shelf

Using Shelf‐Edge Transport Composition and Sensitivity Experiments to Understand Processes Driving Sea Level on the Northwest European Shelf

Are Ocean Reanalyses Useful for Earth Rotation Research?

Are ocean reanalyses useful for Earth rotation research?

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