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SUMMARY:Self-assembly in stratified fluids and extreme depth fluctuations 
 in high-altitude Himalayan lakes - Richard Mclaughlin\, University of Nort
 h Carolina
DTSTART:20231009T120000Z
DTEND:20231009T130000Z
UID:TALK206296@talks.cam.ac.uk
CONTACT:Prof. John R. Taylor
DESCRIPTION:We first discuss experiments and modeling of a new phenomenon 
 we discovered in our fluids lab in which particles suspended at similar de
 pths in stratified water experience an effective attractive force which ar
 ises from diffusion induced flows.  These flows lead to particles forming
  molecule-like assemblages which seem to solve jig-saw like puzzles on the
 ir way to forming a large scale\, compact aggregate disc.  This led us to
  seek such phenomena in the environment through a field campaign in pristi
 ne\, high altitude stratified Himalayan lakes.  This resulted in an unexp
 ected finding concerning seasonal depth fluctuations of the Gokyo lake sys
 tem.  Himalayan lakes represent critical water resources\, culturally imp
 ortant waterbodies\, and potential hazards. We found that some of these la
 kes experience dramatic water-level changes\, responding to seasonal monso
 on rains and post-monsoonal draining. To address the paucity of direct obs
 ervations of hydrology in retreating mountain glacial systems\, we will re
 view our field program focused on a series of high altitude lakes in Sagar
 matha National Park\, adjacent to Ngozumba\, the largest glacier in Nepal.
  In situ observations find extreme (>12 m) seasonal water-level changes in
  a 60-m deep lateral-moraine-dammed lake (lacking surface outflow)\, durin
 g a 16-month period (May 2018-Oct 2019)\, equivalent to a 5 million cubic 
 meter volume change annually. The water column thermal structure was also
  monitored over the same period. A hydraulic model is constructed\, valida
 ted against observed water levels\, and used to estimate hydraulic conduct
 ivities of the moraine soils damming the lake and improves our understandi
 ng of this complex hydrological system. Our findings indicate that lake le
 vel compared to the damming glacier surface height is the key criterion fo
 r large lake fluctuations\, while lakes lying below the glacier surface\, 
 regulated by surface outflow\, possess only minor seasonal water-level flu
 ctuations. Lakes adjacent to glaciers may thus  exhibit very different fi
 lling/draining dynamics based on presence/absence of surface outflows and 
 elevation relative to retreating glaciers\, and consequently may have very
  different fates in the next few decades as the climate warms.  Drone vid
 eos of the rugged terrain will be shown\, and we will preview our most rec
 ent dataset (Oct 2019-May 2022).\n\nhttps://www.nature.com/articles/s41467
 -019-13643-y\n\nhttps://www.nature.com/articles/s41598-023-37667-z
LOCATION:MR5\, CMS
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