Collaborative Research: The role of Ice in the response of Large Lakes to a Changing Climate

大型湖泊对气候变化的长期反应还没有得到很好的理解。最近的观测结果表明，冬季冰盖在决定下一个夏季的热条件方面发挥着至关重要的作用，而以前却没有得到充分的重视;高积冰的浓度决定了春季翻转的时间，这反过来又影响了夏季的温度。上级湖冰盖减少的长期趋势正在导致一个持续和更有效的变暖季节，这有助于夏季湖泊温度的上升大大超过空气温度的上升。然而，人们对冰在这一现象中所起的作用以及预测湖泊对气候变化的热响应的能力知之甚少。此外，湖泊对冬季冰盖的热响应对其碳循环至关重要，因为温度可能是地球化学反应速率的唯一最重要的决定因素。浮游植物的营养吸收率和细菌呼吸率等速率同步调节湖泊碳循环。然而，人们对湖泊温度的稳步上升可能对大型湖泊内生化循环的长期稳定性产生的影响知之甚少。该项目将填补这些知识空白，并从根本上了解冰在确定大型湖泊中温度和碳的完整年度和年际循环中的作用。以下问题与上级湖有关？的物理和地球化学将解决：1）是什么主要负责设置冰的形成量？2)冰形成的空间和时间变化在决定整个湖泊的夏季条件中起什么作用？3)混合层深度的趋势是什么？4)温度升高和冰盖减少是否在湖泊的长期质量平衡中发挥了作用，并导致了过去几十年来水位下降的总趋势？5)多少钱啊？信息？关于热量和碳，如果有的话，是从一年传递到下一年的？6)冰川融化的逐渐提前、夏季温度的升高和温度分层的增强对生物生产和碳循环有什么影响？该项目将提高我们对湖泊水位的理解，这是航运业的一个重要因素。这一前所未有的数据集将提供给各种湖泊建模者。冰和地球化学建模方面的专业知识也将得到扩展。

The long-term response of large lakes to climate change is not well understood. Recent observational results have shown that winter ice cover plays a vital and previously underappreciated role in determining thermal conditions the following summer; the concentration of high albedo ice determines the timing of the spring overturn, which in turn affects summer temperatures. A long-term trend towards lesser ice cover in Lake Superior is causing a sustained and more effective warming season that is contributing to a rise in summer lake temperatures in significant excess of the rise in air temperature. However, the role that ice plays in this phenomenon and the ability to predict the thermal response of the lake to climate change is poorly understood. In addition, the thermal response of the lake to winter ice cover is critical to its carbon cycle, because temperature is perhaps the single most important determinant of biogeochemical reaction rates. Rates such as nutrient uptake rates by phytoplankton and bacterial respiration rates work in synchrony to regulate the lake carbon cycle. Nevertheless, little is known about what effect steadily rising lake temperatures may have on the long-term stability of biochemical cycles within large lakes. This project will fill in these gaps in knowledge and to gain a fundamental understanding of the role of ice in determining the full annual and interannual cycles of temperature and carbon in large lakes. The following questions that pertain to Lake Superior?s physics and biogeochemistry will be addressed: 1) What is primarily responsible for setting the amount of ice formation? 2) What role does the spatial and temporal variability of ice formation play in determining lake-wide summer conditions? 3) What are the trends in mixed layer depth? 4) Are increased temperatures and reduced ice cover playing a role in the long-term mass balance of the lake, and contributing to the general trend of lower water over the last few decades? 5) How much ?information? regarding heat and carbon, if any, is passed from one year to the next? 6) What is the impact of a progressively earlier ice melt, higher summer temperatures, and stronger thermal stratification on biological production and carbon cycle? The project will improve our understanding of lake levels, a significant factor to the shipping industry. The unprecedented dataset will be available to a variety of lake modelers. Expertise in ice and biogeochemical modeling will also be broadened.