WHOI PO

Navy Masters students will give their PO thesis presentations.

Speaker: Keefe Rafferty
Title: Characterizationof the East China Sea Continental Shelf Circulation Northeast of TaiwanSurrounding Mien-Hua Canyon
Abstract: Submarine canyons have a proven and directinfluence on continental shelf circulation and flow dynamics, especially inrelation to western boundary currents. There are two key circulation featuresnortheast of Taiwan on the East China Sea continental shelf: (1) the cold dome,a cyclonic feature that appears primarily in summer and is associated withupwelling, and (2) Kuroshio intrusions onto the continental shelf in thevicinity of Mien-Hua Canyon. This paper is a descriptive physical oceanographystudy with a focus on characterizing the circulation patterns northeast ofTaiwan surrounding Mien-Hua Canyon, closely correlating these patterns with themigration of the Kuroshio and its variability and intrusions onto the southernEast China Sea continental shelf, leading to the formation of the cold dome.The Institute of Oceanography at the National Taiwan University and WHOIexecuted a joint international field survey at Mien-Hua Canyon aiming toimprove the understanding of canyon flow dynamics between the East China Seacontinental shelf northeast of Taiwan and the Kuroshio as the North PacificGyre westward boundary current. This joint oceanographic expedition expands onprevious joint US/Taiwan physical oceanographic and ocean acoustic studies inthe China Seas dating back to ASIAEX in the South China Sea during 2000-2001 andQPE in the East China Sea during 2008-2009. The strengthening and weakening of Kuroshiotransport and intensity northeast of Taiwan is closely correlated to thetimescales of mesoscale westward propagating eddies arriving to the East TaiwanChannel. When a canyon has a Rossby number ~1 or Rossby radius equivalent tothe width of the canyon in a region of left-bounded flow, induced cyclonic flowwill experience an upwelling regime within the canyon system with dominantupwelling located at the downstream canyon rim vertically constrained by RossbyHeight. Observational analysis of canyon bottom moored ADCPs and verticaltemperature arrays supports previous theory on submarine canyon dynamics on acontinental shelf. Satellite sea surface temperature and absolute dynamic topographyobservations render the formation of a cold dome northeast of Taiwan coincidentwith this joint oceanographic survey.


Speaker: Lilli Hirth 
Title: Air-Ice-OceanInteractions Under a Summer Arctic Cyclone: Observations from two Ice-TetheredProfilers
Abstract: An Arctic cyclone passed over twoIce-Tethered Profilers (ITPs) in the Western Arctic Ocean on 28 July 2020. EachITP measured ocean conditions from 7 to 750m depth, collecting data immediatelybefore and after the storm that is used to quantify changes in oceanconditions. Pre- storm conditions were similar for ITP113 and ITP114, and themixed layer at both locations became deeper and saltier due to the storm. Therewere post-storm differences between ITP113 and 114, with ITP114 having a mixedlayer that was 5 m deeper, 0.8 g/kg saltier and 0.05°C colder than for ITP113.These differences resulted from differing amounts of precipitation and surfacemelt, with shallower mixed layers resulting where there was a larger freshwaterinput. Overall, ocean freshening corresponded to total ice melt of 37cm forITP113 and 14cm for ITP114. The freshwater can be attributed to an estimated4-7 cm of precipitation, and 2-4 cm of melt due to ocean heat entrainment, withthe remainder inferred to be from surface ice melt, or past melt that remainedshallower than 5 m depth. Post-storm mixed layer depths differences have thepotential to impact the ice and ocean throughout summer and fall by changingthe amount of solar radiation stored within the ocean. These observations fromneighboring ITPs provide insights into the effects of Arctic cyclones on upperocean conditions, and the feedback between storms, ocean conditions, and seaice cover.