| Title | Equatorial Kelvin waves generated in the western tropical Pacific Ocean trigger mass and heat transport within the Middle America Trench off Costa Rica |
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| Author | Thomson, R E; Davis, E E |
| Source | Journal of Geophysical Research, Oceans vol. 122, issue 7, 2017 p. 5850-5869, https://doi.org/10.1002/2017JC012848  Open Access |
| Image |  |
| Year | 2017 |
| Alt Series | Natural Resources Canada, Contribution Series 20182001 |
| Publisher | Wiley-Blackwell |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf (Adobe® Reader®); html |
| Area | Pacific Ocean; Nicoya Peninsula; Costa Rica |
| Lat/Long WENS | -88.0000 -84.0000 11.5000 8.0000 |
| Subjects | geophysics; tectonics; surficial geology/geomorphology; seabottom temperatures; turbidity currents; water circulation patterns; geophysical interpretations; intrusions; sills; boreholes; satellite
geodesy; oceanography; currents; tides; models; marine sediments; suspended sediments; earthquakes; sea level fluctuations; statistical analyses; Middle America Trench; Fisher Sill; El Nino; La Nina; Madden-Julian Oscillation; 2012 Nicoya Earthquake;
Fisher Basin |
| Illustrations | location maps; geoscientific sketch maps; bathymetric profiles; tables; time series; spectra |
| Program | Public Safety Geoscience Assessing Earthquake Geohazards |
| Program | Ocean Drilling Program |
| Released | 2017 07 25 |
| Abstract | Sequences of correlated seafloor temperature, current velocity, and acoustic backscatter events recorded at Ocean Drilling Program (ODP) sites at 4300 m depth in the Middle America Trench have been
inferred to result from tidally induced turbidity currents generated in the vicinity of the 3300 m deep sill at the southern end of the trench. New data from the borehole observatories extend the temperature records to 11 years (November 2002 to
December 2013) and confirm the highly episodic nature of the events. We present satellite altimetry data and ocean circulation model results to show that event timing is correlated with intraseasonal Kelvin wave motions in the equatorial Pacific. The
observed temperature events had a mean (±1 standard deviation) occurrence interval of 61 (±24) days, which spans the periods of the first two baroclinic modes. Lag times between peak bottom water temperatures at the ODP sites and the passage of
eastward-propagating Kelvin wave crests at locations in the eastern equatorial Pacific are consistent with the time for mode-1 waves to propagate to the southern end of the trench at a mean phase speed of 2.0 m s?1. Findings indicate that Kelvin wave
currents augment tidal motions in the vicinity of the sill, triggering turbidity currents that travel northwestward along the trench axis at mean speeds of ?0.1 m s?1. We conclude that mode-1 (or, possibly, mixed mode-1 and mode-2) baroclinic Kelvin
waves generated by large-scale atmospheric processes in the western tropical Pacific lead to heat and mass transport deep within Middle America Trench in the eastern tropical Pacific. |
| Summary | (Plain Language Summary, not published)
Data from Ocean Drilling Program sites at 4300 m depth in the Middle America Trench off Costa Rica reveal that turbidity currents deliver relatively warm
water to the bottom of the trench roughly every 62 days. These events last on average about 30 days and appear to begin with sediment suspension in the vicinity of the shallow (3300 m) deep sill at the southern end of the trench. New data from the
ODP sites, combined with satellite altimetry records and results from a general ocean circulation model, show that events are closely linked to eastward-propagating Kelvin waves of sub-seasonal period originating in the western equatorial Pacific.
Findings indicate that baroclinic Kelvin waves generated by large-scale atmospheric processes, such as the Madden-Julian Oscillation in the western tropical Pacific, lead to heat and mass transport deep within Middle America Trench nearly 10,000 km
to the east. |
| GEOSCAN ID | 310541 |
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