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  • Nature Research  (1)
  • Springer Berlin Heidelberg  (1)
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  • 1
    Publication Date: 2023-06-22
    Description: We revisit the problem of modeling the ocean’s contribution to rapid, non-tidal Earth rotation variations at periods of 2–120 days. Estimates of oceanic angular momentum (OAM, 2007–2011) are drawn from a suite of established circulation models and new numerical simulations, whose finest configuration is on a 1⁄ 6◦ grid. We show that the OAM product by the Earth System Modeling Group at GeoForschungsZentrum Potsdam has spurious short period variance in its equatorial motion terms, rendering the series a poor choice for describing oceanic signals in polar motion on time scales of less than ∼2 weeks. Accounting for OAM in rotation budgets from other models typically reduces the variance of atmosphere-corrected geodetic excitation by ∼54% for deconvolved polar motion and by ∼60% for length-of-day. Use of OAM from the 1⁄ 6◦ model does provide for an additional reduction in residual variance such that the combined oceanic–atmospheric effect explains as much as 84% of the polar motion excitation at periods 〈 120 days. Employing statistical analysis and bottom pressure changes from daily Gravity Recovery and Climate Experiment solutions, we highlight the tendency of ocean models run at a 1◦ grid spacing to misrepresent topographically constrained dynamics in some deep basins of the Southern Ocean, which has adverse effects on OAM estimates taken along the 90◦ meridian. Higher model resolution thus emerges as a sensible target for improving the oceanic component in broader efforts of Earth system modeling for geodetic purposes.
    Description: Austrian Science Fund http://dx.doi.org/10.13039/501100002428
    Description: National Aeronautics and Space Administration http://dx.doi.org/10.13039/100000104
    Description: https://isdc.gfz-potsdam.de/ggfc-oceans/
    Description: https://doi.org/10.5281/zenodo.4707150
    Description: http://rz-vm115.gfz-potsdam.de:8080/repository/
    Description: https://ifg.tugraz.at/ITSG-Grace2018
    Description: ftp://isdcftp.gfz-potsdam.de/grace/Level-1B/GFZ/AOD/RL06/
    Description: https://ecco-group.org/products-ECCO-V4r4.htm
    Keywords: ddc:550.2 ; Earth rotation ; Geophysical fluids ; Excitation ; Ocean bottom pressure
    Language: English
    Type: doc-type:article
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  • 2
    Publication Date: 2022-05-26
    Description: Author Posting. © The Authors, 2018. This is the author's version of the work. It is posted here by permission of Nature Research for personal use, not for redistribution. The definitive version was published in Piecuch, C. G., Huybers, P., Hay, C. C., Kemp, A. C., Little, C. M., Mitrovica, J. X., Ponte, R. M., & Tingley, M. P. (2018). Origin of spatial variation in US east coast sea-level trends during 1900-2017. Nature, 564(7736), 400-404, doi:10.1038/s41586-018-0787-6.
    Description: Identifying the causes of historical trends in relative sea level—the height of the sea surface relative to Earth’s crust—is a prerequisite for predicting future changes. Rates of change along the U.S. East Coast during the last century were spatially variable, and relative sea level rose faster along the Mid-Atlantic Bight than the South Atlantic Bight and Gulf of Maine. Past studies suggest that Earth’s ongoing response to the last deglaciation1–5, surface redistribution of ice and water 5–9, and changes in ocean circulation9–13 contributed importantly to this large-scale spatial pattern. Here we analyze instrumental data14, 15 and proxy reconstructions4, 12 using probabilistic methods16–18 to show that vertical motions of Earth’s crust exerted the dominant control on regional spatial differences in relative sea level trends along the U.S. East Coast during 1900–2017, explaining a majority of the large-scale spatial variance. Rates of coastal subsidence caused by ongoing relaxation of the peripheral forebulge associated with the last deglaciation are strongest near North Carolina,Maryland, and Virginia. Such structure indicates that Earth’s elastic lithosphere is thicker than has been assumed in other models19–22. We also find a significant coastal gradient in relative sea level trends over this period that is unrelated to deglaciation, and suggests contributions from twentieth-century redistribution of ice and water. Our results indicate that the majority of large-scale spatial variation in longterm rates of relative sea level rise on the U.S. East Coast was due to geological processes that will persist at similar rates for centuries into the future.
    Description: Funding came from Woods Hole Oceanographic Institution’s Investment in Science Fund; Harvard University; NSF awards 1558939, 1558966, and 1458921; and NASA awards NNH16CT01C, NNX17AE17G, and 80NSSC17K0698. We acknowledge helpful conversations with S. Adhikari, B.D. Hamlington, F.W. Landerer, S.J. Lentz, and P.R. Thompson. Comments from three anonymous referees and the editor, Michael White, are greatly appreciated.
    Description: 2019-06-18
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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