ANADYR STRAIT 

 i 



ANADYR STRAIT 

 i 



ANADYR STRAIT 

 i 



Fig. 10. North-south section through Anadyr Strait from a .Vd numerical model ( Deleersniider& Nihoul, 1 988) showing (A) vertical velocities upward just north 

 of the strait; (B) breakdown of stratification just north of the strait; and (C I high concentrations of turbulent kinetic energy just north of the strait. The.se 

 result from physical constriction of the flow by the topography, and mix the water columns vertically, "resetting" the ecosystem. 



The import to the ecosystem of nonconservative transport 

 through Chirikov basin is a large variation in residence times 

 of water parcels in the basin. This variability affects not so 

 much the production but the proportion of production exported 

 versus the proportion sequestered in the basin as sediments. 



During the ISHTAR field programs, between six and ten 

 moorings with current meters were deployed each year in the 

 Chirikov basin. From these records, residence times of water 

 parcels entering the basin through Anadyr and Shpanberg 

 Straits were estimated. The data from each meter were 

 considered to be representative of water in an area surrounding 

 the mooring location extending halfway to adjacent meters. 

 Mean daily excursions of water parcels were calculated and 

 plotted sequentially, using the current data from the closest 

 meter. The residence time is the number of days elapsing 

 between the entrance of a water parcel through Anadyr Strait 

 until its exit through Bering Strait. 



Reconstructed water parcel trajectories representative of 

 various length residence times are shown in Fig. 1 1 . The most 

 typical residence times in summer are about two weeks, when 

 the flow is steadily northward with little variation. Under these 

 flow conditions, water parcels take a relatively direct route 

 from Anadyr into the center of the basin, then veer left and 

 move directly to Bering Strait. The trajectories of minimum 

 residence times are much the same — nearly a direct path 

 between Anadyr and Bering Straits — and occur when the 

 current speeds in both straits are exceptionally strong. Medium 

 duration residences of three to four weeks occur when currents 

 in the straits are still generally northward, but much slower, 

 particularly in Bering Strait. During these times, the water 

 entering through Anadyr floods eastward across the basin. The 

 longest residence times are when flow actually reverses in the 

 system; water parcels spend time describing gyres in the basin 

 interior. 



The residence times of water parcels in summer has been 

 quite different over the four years of intensive study. The times 

 for water entering through Anadyr Strait, beginning in eariy 

 July each year 1985-1988, estimated for alternate days, are 

 graphed in Fig. 1 2. The times are plotted according to the day 

 the water entered the basin. The measured residence times vary 

 by more than a factor of 5, from a very rapid transit of 9 days 

 (mean speed -34 cm/s) to more than 50 days. The variability 



60° 



174° 



Fig. 11. 



RECONSTRUCTED WATER PARCEL TRACKS 



172° 



168° 



166° 



Reconstructed trajectories of Anadyr Current water parceLs, 

 illustrating different residence times. Coding: above is residence 

 time in days; below is (year: Julian day of ingress through Anadyr 

 Strait ). Note that with longer residence times water parcel excursions 

 extend farther east; very long residence times involve gyre trajectories 

 associated with tlow reversals in the svstem. 



23 



