Characteristics of ocean bottom roughness for several seamounts derived from multibeam bathymetric data

Abstract

ABSTFACTMultibeam bathymetric systems offer t o r e v o l u t i o nize our understanding of the ocean bottom and i t s major s t r u c t u r a l f e a t u r e s by providing highljr detailed neasurelcents of the bottom. F u r t h e r , multibean measurements yield bottom depth 2s a function of both spztiai coordinates (i.e. alongt r a c k 2nd a c r o s s -t r a c k ) . The depth resolution is s u f f i c i e n t l y f i n e t h a t c o n v e n t i o n a l c o n t o u r c h a r t s vould never incorporate a l l the information availa b l e i n t h e a u l t i b e a n data. As a n a l t e r n a t i v e t o s,Jch de'erminlszic presentations, i: can be suggeste d t h a t s t a t i s t L C e l c h a r s c t e r i z a t i m s ' De developed f o r t o p o g r a p h i c v a r i a b i l i t y a t h o r i z o n t a l s c a l e s which a r e small i n comparisor. t o t h e o v e r a l l dimensions of the feature of i n t e r e s t . Ve here discuss the stlldy of roagh topography on several seamounts by means of multibean bathymetry. The bottom topography I s analyzed in terms of numerous samples of 1503 m x 1600 n extent. A. primary quantity of intere s t i s t h e rms value of t h e r e s i d u a l :opogra?hy. The AwAt;erc of v a r i a b i l i t y f o r t h e rzs values i s 3es.ribed for several seanoucts and shown t o have c e r t a i n o v e r a l l similerities. INTROCLJCTIOPi Multibeam bathymetric swath napping systems such as SeabPam a r d S.A.S.S. o f f e r t o r e v o l u t i o n i z e our understanding of the ocean bottom and i t s major s t r u c t :~r a l f e a t u r e s by p r w i d i n g h i g h l y d e t a i l e d measurements of t h e bottom. P r i o r t o t h e 6 e v e l o pment of these systems xost af the bathynetric i n f o r m t i o n e x i s t e d i n t h e form of wide beam echo-sounder surveys from which only botton information i n t h e a l o n g t r a c k d i r e c t i o n o f t h e s:lmejr could be readily extracted. MLtibeam systems, however yield bottom depth as a function of b o t h t h e a l o n g t r a c k a n d c r o s s t r a c k d i r e c t i o n s of a silrvef and as a r e s u l t p r o v i d e a h i g h l y d e t a i l e d two-dimensional description of the ocean floor. h r t h e r m o r e , t h e d e p t h reso1u:ion of modern multibeam systems i s s u f f i c i e n t l y f i n e t h a t c o n t o u r c h a r t s et conventional scales of p r e s e n t a t i o n w i l l probably never incorporate a l l of t h e i n f o r m t i o n a v a i l a b l e f r o n t h e system. A s a n a l t e r n a t i v e t o such Presentations, it can be suggested that s t a t i s t i c a l c h a r a c t e r i z a t i o n s ought t o be developed f o r t o p o g r a p h i c v a r i a b i l i t y a t h o r i z o n t a l s c a l e s whlch a r e small i n comparison t o t h e o v e r a l l dimensions of t h e l a r g e s c a l e f e a t u r e s of i n t e r e s t . Thus the information available from multibeam bathyaetric systems can be divided into two c h a r a c t e r i z a t i o n s , one d e t e r m i n i s...