The simulated response of lakes to changes in annual and seasonal precipitation: implication for Holocene lake-level changes in northern Europe

Experiments with a coupled lake-catchment model show that lakes in temperate humid climates are highly sensitive to changes in both mean annual and seasonal precipitation. Simulations of three lakes from northern Europe (Lake Bysjön, Sweden; Lakes Karujärv and Viljandi, Estonia) show that lake level is more sensitive to decreases than to increases in precipitation. Increased precipitation results in increased runoff, but this is largely compensated by increased outflow and the change in lake level is small. Reductions in winter (November-April) precipitation have a bigger impact on simulated lake level than changes in summer (May-October) precipitation. Evapotranspiration is highly sensitive to reduction in precipitation, particularly in summer, but relatively insensitive to increased precipitation. Runoff decreases more rapidly with a decrease in winter precipitation and increased precipitation will linearly increase runoff. To match observed lake-level changes at Lake Bysjön at 9000 and 6000 y. BP (ca 6–7 m and 4–5 m lower than present respectively), without changing other climate parameters, would require a decrease in annual precipitation of about 400–500 mm and 350–400 mm respectively. The same changes in lake level could be produced by decreasing precipitation in winter precipitation by about –200 mm and about −175 mm respectively. The simulations suggest that a lake, which is large relative to its catchment, is more likely to register lake-level changes caused by changes in climate