Interaction of high frequency internal waves and the boundary layer on the continental shelf

I n t e r m i t t e n t , shoreward propagating packets o f h i g h frequency f i r s t mode i n t e r n a l waves a r e common on the c o n t i n e n t a l shel f when t h e water column i s s t r a t i f i e d and may induce l a r g e f l u c t u a t i o n s i n near bottom v e l o c i t y .Simp1 e t h e o r e t i c a l considerations here 1 ead t o an approximate method f o r e s t i m a t i n g those q u a n t i t i e s o f most i n t e r e s t f o r the bottom boundary 1 ayer i n t e r a c t i o n probl em.Examination o f data from the p i 1 o t Coastal Ocean Dynamics Experiment (CODE I ) shows t h a t near bottom v e l o c i t y f l uctuations i n t h e high frequency i n t e r n a l wave band were dominated b y shoreward propagating, i n t e r m i t t e n t mode 1 i n t e r n a l events.P r e d i c t i o n s o f CODE I i n t e r n a l wave c h a r a c t e r i s t i c s u s i n g t h e above approximate method a r e shown t o be good.A boundary 1 ayer model i s developed, which a1 1 ows f o r t h e nonlinear i n t e r a c t i o n o f surface waves, i n t e r n a l waves, and a steady c u r r e n t over a rough bottom.Modeling r e s u l t s suggest t h a t i n t e r n a l waves w i l l s i g n i f i c a n t l y enhance t h e s t r e s s f e l t b y the steady current, and can i ncrease t h e v a r i a b i l i t y and decrease t h e re1 i a b i 1 i t y o f boundary 1 ayer measurements by t h e " l o g p r o f i l e " technique, when the waves are present.Theoretical d i s s i p a t i o n o f i n t e r n a l wave energy i n t h e bottom boundary l a y e r i s found t o be s i g n i f i c a n t l y enhanced i n the presence o f surface waves and currents, and may be important t o t h e o v e r a l l i n t e r n a l wave energy balance on the shel f.