Deep‐water renewal in Lake Issyk‐Kul

The deep‐water renewal rates of Lake Issyk‐Kul are studied using the time‐dependent anthropogenically produced tracers sulfur hexafluoride (SF 6 ), chlorofluorocarbons (CFCs) and tritium‐helium‐3. SF 6 and the CFCs are used to calibrate a mixing model from which the vertical age distribution is calculated and found to be comparable to the SF 6 apparent ages. Based on this model, the mean age of the water below 100 m depth is 6.1 yrs. The mean oxygen consumption rate for the same depth range is 6.4 μmol kg −1 yr −1 and the mean remineralization rates for nitrate, phosphate and silicate are 0.53, 0.003 and 0.67 μmol kg −1 yr −1 , respectively.