Effect of climate change on stratification of a small, monomictic, temperate, karstic lake (Lake Kozjak, Croatia)

Abstract

Abstract As delicate closed systems, lakes are extremely vulnerable to climate change. In this paper, we examine Lake Kozjak, Croatia, a small karstic, monomictic lake that belongs to the Plitvice Lake system. The Plitvice Lakes represent a special hydrogeological karstic phenomenon that is closely dependent on a delicate biochemical balance necessary for tufa formation. We apply a simple one-dimensional model for monomictic lakes, SIMO v.1.0, to predict the water temperature at Lake Kozjak in three future scenarios (RCP2.6, RCP4.5 and RCP8.5) for the period between 2006 and 2100. The model captures the seasonal stratification and deepening of the thermocline as well as convective mixing. The results show that the significant increase in the lake water temperature that is expected in the more pessimistic scenarios is not accompanied by significant stratification strengthening due to significant heating of not only the epilimnion but also the hypolimnion. However, significant lengthening of the stratification period is observed even for the most stringent scenario, RCP2.6.