Trapped diurnal internal tides, propagating semidiurnal internal tides, and mixing estimates in the California Current System from sustained glider observations, 2006-2012

TitleTrapped diurnal internal tides, propagating semidiurnal internal tides, and mixing estimates in the California Current System from sustained glider observations, 2006-2012
Publication TypeJournal Article
Year of Publication2015
AuthorsJohnston T.MS, Rudnick D.L
JournalDeep-Sea Research Part Ii-Topical Studies in Oceanography
Volume112
Pagination61-78
Date Published2015/02
Type of ArticleArticle
ISBN Number0967-0645
Accession NumberWOS:000350921700007
Keywordscontinental-slope; Cross-shore; decay; hawaiian ridge; internal tides; Mixing parameterizations; new-england shelf; santa-monica basin; seasonal cycle; Shear; tidal energy; turbulent dissipation; upper ocean; waves; yermak plateau
Abstract

From 2006-2012, along 3 repeated cross-shore transects (California Cooperative Oceanic Fisheries Investigations lines 66.7, 80, and 90) in the California Current System, 33 609 shear and 39 737 strain profiles from 66 glider missions are used to estimate mixing via finescale parameterizations from a dataset containing over 52 000 profiles. Elevated diffusivity estimates and energetic diurnal (D-1) and semidiurnal (D-2) internal tides are found: (a) within 100 km of the coast on lines 66.7 and 80 and (b) over the Santa Rosa-Cortes Ridge (SRCR) in the Southern California Bight (SCB) on line 90. While finding elevated mixing near topography and associated with internal tides is not novel, the combination of resolution and extent in this ongoing data collection is unmatched in the coastal ocean to our knowledge. Both D-1 and D-2 internal tides are energy sources for mixing. At these latitudes, the D-1 internal tide is subinertial. On line 90, D-1 and D-2 tides are equally energetic over the SRCR, the main site of elevated mixing within the SCB. Numerous sources of internal tides at the rough topography in the SCB produce standing and/or partially-standing waves. On lines 66.7 and 80, the dominant energy source below about 100 m for mixing is the D-1 internal tide, which has an energy density of the D-2 internal tide. On line 80, estimated diffusivity, estimated dissipation, and D-1 energy density peak in summer. The D-1 energy density shows an increasing trend from 2006 to 2012. Its amplitude and phase are mostly consistent with topographically-trapped D-1 internal tides traveling with the topography on their right. The observed offshore decay of the diffusivity estimates is consistent with the exponential decay of a trapped wave with a mode-1 Rossby radius of 20-30 km. Despite the variable mesoscale, it is remarkable that coherent internal tidal phase is found. (C) 2014 Elsevier Ltd. All rights reserved.

DOI10.1016/j.dsr2.2014.03.009
Student Publication: 
No