Brkić Željka
Croatian Geological Survey, Department of Hydrogeology and Engineering Geology, Sachsova 2, Zagreb, Croatia.
Heliyon. 2023 Aug 18;9(8):e19248. doi: 10.1016/j.heliyon.2023.e19248. eCollection 2023 Aug.
Global warming has been monitored for many years. The increase in air temperature and changes in the distribution and frequency of high temperatures are recorded continually. Lakes are one of the important water resources for aquatic ecosystems and water supply, which are significantly affected by global warming. The increase in lake water temperature increases the evaporation from the free lake surface, lowering the lake level, and changes the water quality. In the last few decades, analysis of changes in lake water temperature has been increasing. In situ measurements of water temperature in Vrana Lake on Cres island (Croatia), the largest freshwater lake on the Mediterranean islands, were analysed over 43 years. The results showed that the mean annual lake surface water temperature (LSWT) increased by 0.47 °C decade-1 (p < 0.0001). The increase in the mean annual lake summer surface water temperature (July-September) was 0.44 °C decade-1 (p < 0.0001), and the maximum annual LSWT was 0.56 °C decade-1 (p < 0.0001). All these amounts are in accordance with the published data on the increase in water temperature in the investigated European lakes. The number of days with LSWT higher than 25 °C increased by almost 9 d decade-1. An increase in the minimum LSWT (0.17 °C decade-1) corresponding to isothermal conditions was also determined but was not statistically significant. The minimum mean monthly LSWT increased by 0.36 °C decade-1 (p < 0.0001). Because the increase in water temperature can negatively affect the lake's ecosystem, and become a threat to safe water supply; LSWT, thermal stratification and evaporation should be continuously monitored. The impacts of climate warming on the lake stratification and aquatic ecosystems need to be further investigated.
全球变暖已被监测多年。气温上升以及高温分布和频率的变化都在持续记录中。湖泊是水生生态系统和供水的重要水资源之一，受到全球变暖的显著影响。湖水温度升高会增加湖泊自由水面的蒸发量，降低湖泊水位，并改变水质。在过去几十年里，对湖水温度变化的分析一直在增加。对地中海岛屿上最大的淡水湖——克罗地亚克雷斯岛的弗拉纳湖43年的水温原位测量数据进行了分析。结果表明，年平均湖泊表层水温（LSWT）以每十年0.47℃的速度上升（p < 0.0001）。年平均湖泊夏季表层水温（7月至9月）的上升速度为每十年0.44℃（p < 0.0001），年度最高LSWT为每十年0.56℃（p < 0.0001）。所有这些数值都与已发表的有关所研究的欧洲湖泊水温上升的数据一致。LSWT高于25℃的天数几乎以每十年9天的速度增加。还确定了对应等温条件下最低LSWT的上升（每十年0.17℃），但不具有统计学意义。最低月平均LSWT以每十年0.36℃的速度上升（p < 0.0001）。由于水温上升会对湖泊生态系统产生负面影响，并对安全供水构成威胁；因此应持续监测LSWT、热分层和蒸发情况。气候变暖对湖泊分层和水生生态系统的影响需要进一步研究。
