. Changes in the vertical arrival angle of sound rays as they pass through a front can cause towed array bearing errors. It is clear that any one of these effects can have a significant  impact  on  ASW  operations.  Together  they determine the mode and range of sound propagation and thus  control  the  effectiveness  of  both  short-  and long-range acoustic systems. The combined effect of these characteristics is so complex that it is not always possible to develop simple rules for using ocean fronts for ASW tactics. For example, the warm core of the Gulf Stream south of Newfoundland will bend sound rays  downward  into  the  deep  sound  channel,  thereby enhancing  the  receiving  capability  of  a  deep  receiver. The same situation with a slightly shallower bottom south of Maine may create a bottom-limited situation, and the receiving capability at the same hydrophore will be impeded. In view of this, the acoustic effects of a front must be determined for each particular situation by  using  multiprofile  (range-dependent  environment) acoustic  models.  The  input  for  these  models  can  come from detailed oceanographic measurements, or from historical  data  in  combination  with  surface  frontal positions  obtained  from  satellites. DETERMINING FRONTAL POSITION USING SATELLITE DATA Most  fronts  exhibit  surface-temperature  signatures that can be detected by satellite infrared (IR) sensors and are used in determining frontal positions. Figure 9-17 is an example of a satellite IR image obtained by the TIROS-N showing the location of the Gulf Stream and formation  of  a  warm  ring.  Because  surface-temperature gradients  are  not  always  reliable  indicators  of  the subsurface front, satellite images must be interpreted by a skilled analyst, preferably in combination with data from   other   sources   such   as   BTs.   Automatic interpretation  of  satellite  data  is  also  being  developed using   techniques   generally   known   as   automatic imagery-pattern  recognition  or  artificial  intelligence. Now let’s discuss oceanographic effects on mine warfare (MIW).  Environmental  Effects  on  Weapons Systems  and  Naval  Warfare  (U),  (S)RP1,   provides further detail on this subject. MINE WARFARE (MIW) LEARNING   OBJECTIVES   Recognize   the parameters affecting MIW operations. Identify the  various  mine  hunting  sonars.  Be  familiar with  the  procedures  for  obtaining  MIW  support products. MIW  is  the  strategic  and  tactical  use  of  sea mines  and  their  countermeasures.  MIW  may be   offensive   (mining   to   interfere   with   enemy ship   movement)   or   defensive   (mining   to   defend friendly waters [mine-countermeasures]) in nature. Mine  warfare  is  almost  always  conducted  in nearshore areas that present special environmental conditions not usually encountered in open ocean areas, including: .  Sound  speed  that  is  highly  dependent  upon salinity. Although salinity may be treated as constant for open ocean areas, fresh water runoff creates strong salinity gradients in nearshore areas. l Ambient noise that is higher than normal. l Biologic activity levels and diversity that are higher. . Nearshore areas that typically have a high level of  nonmilitary  activity. . Land runoff that generates much more turbidity than for open ocean areas. MINE WARFARE ENVIRONMENTAL SUPPORT MIW  planning  (mining  and  mine  countermeasures) requires  a  considerable  environmental  input.  The following   parameters   should   be   considered   for discussion  in  any  MIW  environmental  support package: Water depth Physical properties of water column Tides Currents Sea ice Bottom  characteristics 9-18