Answer the following question after reading \"Rapid and highly variable warming
ID: 144015 • Letter: A
Question
Answer the following question after reading "Rapid and highly variable warming of lake surface waters around the globe" by O Reilly
Link: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015GL066235
1. Please describe the goals of the study. Based on your reading of
the paper, according to the authors why is this an important subject for study?
2. Briefly describe the methods used by the authors to conduct their study.
3. What were the major findings of this paper? In particular, how fast (on average) is
lake surface temperature increasing, and how does the warming rate vary among different lake
types? What lake type(s) have the fastest warming rates? Which type(s) have the slowest
warming rates?
4. In some lakes, surface water temperature is increasing faster than air temperature.
What lakes show this pattern, and what can explain how water temperature increase faster
than air temperature?
4. What do you think is the most important graphic (figure or table) in the paper, in
terms of conveying the findings of the research? Why?
5. What might be the next steps in this line of research? What kinds of additional data or studies might be
needed, after this study, to advance our understanding of how and why lake temperatures are
increasing?
Explanation / Answer
1) The goal of the study is to understand the trajectories of climate change in inland waters, as small changes can affect key physical and biological processes through nonlinear dynamics. There are certain relationship between lake surface temperature and some climatic or geomorphic drivers like heat exchange with atmosphere, absorbed solar irradiance, or some local factors, which can affect lake temperatures differently.
2) For the study, the authors used a database containing information about Lake Summer Surface Water Temperature(LSSWT) and climatic variables for past years. For each lake, the temperature anomalies were calculated relative to its 1985–2009 mean. Then linear regression was used across the annual globally averaged anomalies to determine the global LSSWT warming rate. For lakes, only the in situ values were used. Calculations were done in R.
Proximal similarity analysis was also performed in which a z score was calculated based on two characteristics for each lake: its trend value (Sen slope) and its proximity to other lakes with similar values, in different subcontinents.
A regression tree analysis was performed on LSSWT trends to identify factors that correspond with the warming trends observed across the widely distributed lakes in their database, percent variation (R2) explained by the regression tree was calculated.
3) Major findings- Lake summer surface water temperatures (LSSWT) are warming signicantly, with a mean trend of 0.34°C per decade. Although, LSSWT trends range from -0.7 to 1.3°C per decade and show clear regional variation. Warming rates were heterogenous even within regions and in proximities. Diverse climatic and geomorphic factors are responsible for this variation in lake surface water warming.
Laurentian Great Lakes region and in Northern Europe, lakes are warming faster. Also, ice-covered lakes are warming signicantly faster, as much as twice than lakes that do not experience ice cover. Whereas, in contrast, lakes in southeastern North America were warming signicantly more slowly than the global average.
4) In some lakes, surface temperature is warming faster than air temperature, for example, the ice-covered lakes. Earlier summer stratification can result in surface water warming rapidly. Also, summer shortwave radiation trends were signicantly greater for ice-covered lakes(Wilcoxon p < 0.0001), and these lakes also experienced decrease in summer cloud cover. Combination of these things can explain rapid warming of surface water than air temperature.