Figure
4 . Dispersion relation curves of BTRW with periods of 25-40 days. The
purple shading indicates theoretically possible ranges of frequency and
wavenumber for TIW-induced BTRW. A large red circle corresponds to the
33-day period BTRWs. Blue and pink small circles are wavenumbers
estimated from numerical results Ubt and
Vbt. Green and black solid (dashed) arrows are,
respectively, phase and group velocities of TIW-induced BTRW obtained
from Ubt (Vbt).
5 Conclusion
Using long-term in-situ near-bottom current measurements, this study
provides new evidence to confirm that the TIW-induced BTRWs propagate
their energy northward above 10°N in the northeastern Pacific Ocean. The
filtered time series of in-situ near-bottom current velocity shows that
the TIW-induced BTRWs induce a maximum velocity of approximately 3 cm/s
at the near bottom and have variations similar to those of TIWs. Our
results can be the answer to the question about whether barotropic waves
can actually exist in the deep ocean where the near-bottom velocities
are close to zero due to bottom boundary condition (LaCasce, 2017).
It has been also evidenced from numerical simulation that this energy
propagation was caused by the BTRWs, which showed inter-annual
variations because the waves were derived from TIWs. The inter-annual
variations of filtered velocity from numerical simulation and filtered
in-situ observation suggest that the abyssal ocean responds to climate
change, ENSO over the northeastern Pacific Ocean.
Our observation suggests that TIW-induced BTRWs transported the energy
of the equatorial eastern Pacific Ocean to the abyssal ocean in high
latitudes. The effects of TIWs transported to the abyssal ocean in a low
energy environment, due to the lesser vertical gradient of density and
variation of current, can lead to turbulence (Aleynik et al., 2017). The
response of the bottom current is meaningful in that it is possible to
affect the advection of abyssal resources, because the mooring
observation site is located in the Clarion-Clippertone zone. Thus, the
long-term in-situ near-bottom current velocity is also expected to
improve the understanding of the distributions of mineral deposits and
be used as an evaluation element in terms of abyssal mining.
Acknowledgments
Supports for this research were provided by “Test of long-term
monitoring system installation for oceanic environmental changes caused
by accelerated sea-ice melting in the Chukchi Sea (20210540)”, and also
grant 19992001 funded by the Ministry of Oceans and Fisheries of Korea.
Open Research
The filtered near-bottom current velocity data used in figures can be
downloadedhttps://github.com/KNLeeinha/KOMO_CM.gitand will be deposited Zenodo permanently if the manuscript is accepted.
A newly gridded SSH data product was provided by Farrar et al. (2021),
athttps://doi.org/10.5281/zenodo.4541592.
GLORYS12V1 reanalysis data were provided by the CMEMS, from their web
site athttps://doi.org/10.48670/moi-00021.
References
Aleynik, D., Inall, M. E., Dale, A., & Vink, A. (2017). Impact of
remotely generated eddies on plume dispersion at abyssal mining sites in
the Pacific. Scientific Reports , 7(16959), 1−14.https://doi.org/10.1038/s41598-017-16912-2
An, S.-I. (2008). Interannual variation of the tropical ocean
instability wave and ENSO. Journal of Climate , 21(15), 3680−3686.https://doi.org/10.1175/2008JCLI1701.1
Chelton, D. B., Wentz, F. J., Gentemann, C. L., de Szoeke, R. A., &
Schlax, M. G. (2000). Satellite microwave SST observations of
transequatorial tropical instability waves. Geophysical Research
Letters, 27(9), 1239−1242.https://doi.org/10.1029/1999GL011047
Contreras, R. F. (2002). Long-term observations of tropical instability
waves. Journal of Physical Oceanography, 32(9), 2715−2722.https://doi.org/10.1175/1520-0485(2002)032<2715:LTOOTI>2.0.CO;2
Farrar, J. T. (2011). Barotropic Rossby waves radiating from tropical
instability waves in the Pacific Ocean. Journal of Physical
Oceanography, 41(6), 1160−1181.https://doi.org/10.1175/2011JPO4547.1
Farrar, J. T., Durland, T., Jayne, S. R., & Price, J. F. (2021).
Long-distance radiation of Rossby waves from the equatorial current
system. Journal of Physical Oceanography, 51(6), 1947−1966.https://doi.org/10.1175/JPO-D-20-0048.1
Hernández-Guerra, A., & Nykjaer, L. (1997). Sea surface temperature
variability off North-West Africa: 1981–1989. International
journal of remote sensing , 18(12), 2539–2558.https://doi.org/10.1080/014311697217468
Holmes, R. M., & Thomas, L. N. (2016). Modulation of tropical
instability wave intensity by equatorial Kelvin Waves. Journal of
Physical Oceanography , 46(9),2623–2643.https://doi.org/10.1175/JPO-D-16-0064.1
LaCasce, J. M. (2017). The prevalence of oceanic surface modes.Geophysical Research Letters , 44(21), 11097–11105.https://doi.org/10.1002/2017GL075430
Lee, T., Farra, J. T., Arnault, S., Meyssignac, B., Han, W., & Durland,
T. (2017). Monitoring and interpreting the tropical oceans by satellite
altimetry. In D. Stammer & A. Cazenave (Eds.), Satellite
altimetry over ocean and land surfaces (1st ed., pp. 231–270). Boca
Raton, FL: CRC Press.
Legeckis, R. (1977). Long waves in the eastern equatorial pacific ocean:
a view from a geostationary satellite. Science, 197(4309),
1179−1181.https://science.sciencemag.org/content/197/4309/1179
Legeckis, R., Pichel, W., & Nesterczuk, G. (1983). Equatorial long
waves in geostationary satellite observations and in a multichannel sea
surface temperature analysis. Bulletin of the American
Meteorological Society, 64(2), 133−139.https://doi.org/10.1175/1520-0477(1983)064<0133:ELWIGS>2.0.CO;2
Lyman, J. M. (2005). Tropical instability waves as a resonance between
equatorial Rossby waves. Journal of Physical Oceanography, 35(2),
232–254.https://doi.org/10.1175/JPO-2668.1
Lyman, J. M., Johnson, G. C., & Kessler, W. S. (2007). Distinct 17- and
33-day tropical instability waves in subsurface
observations. Journal of Physical Oceanography, 37(4), 855−872.https://doi.org/10.1175/JPO3023.1
Moum, J. N., Lien, R. C., Perlin, A., Nash, J. D., Gregg, M. C., &
Wiles, P. J. (2009). Sea surface cooling at the equator by subsurface
mixing in tropical instability waves. Nature Geoscience , 2(11),
761–765.https://doi.org/10.1038/ngeo657
Philander, S. G. H. (1976). Instabilities of zonal equatorial currents.Journal of Geophysical Research , 81(21), 3725–3735.https://doi.org/10.1029/JC081i021p03725
Shinoda, T., Kiladis, G. N., & Roundy, P. E. (2009). Statistical
representation of equatorial waves and tropical instability waves in the
Pacific Ocean. Atmospheric research, 94(1), 37−44.https://doi.org/10.1016/j.atmosres.2008.06.002
Tchilibou, M., Gourdeau, L., Morrow, R., Serazin, G., Djath, B., &
Lyard, F. (2018). Spectral signatures of the tropical pacific dynamics
from model and altimetry: A focus on the meso-submesoscale range.Ocean Science, 14(5), 1283−1301.