Read the article: \"Rapid and highly variable warming of lake surface waters aro
ID: 144014 • Letter: R
Question
Read the article: "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
The main goal of this study is to better understand and predict global trends of lake warming.
It is an important subject for study because lakes forms a large part of Earth's liquid freshwater system. It is a home of huge variety of flora and fauna and plays a key role in providing cultural ecosystem services to people around the world. Inspite of having such a vast biodiversity, very little measures have been taken to protect it.
Climate change is among the greatest threats to lakes yet empirical knowledge of global lake responses remains fragmented.
Database including lake summer surface water temperatures (LSSWT) derived from in situ and/or satellite measurements were used. It provides a global distribution of lake data. LSSWT were calculated as 3month mean temperatures. The global average warming rate for lake summer surface water temperatures was calculated, following the approach used by the International Panel on Climate Change. For each lake, the temperature anomalies relative to its 1985–2009 mean was calculated. Then linear regression across the annual globally averaged anomalies was used to determine the global LSSWT warming rate. For lakes with both in situ and satellite temperature data, only the in situ values were used. A proximal similarity analysis was completed using the GetisOrd Gi* statistic, and resulting maps were generated in ArcGIS. This analysis identified subcontinent regions on the globe where lake temperatures were trending similarly to surrounding lakes within that area relative to the global trend. A regression tree analysis was performed on LSSWT trends to identify suites of factors that correspond with the warming trends observed across the widely distributed lakes in database used.
The major findings showed that lake summer surface water temperatures (LSSWT) were warming significantly, with a mean trend of 0.34°C decade1 (95% CI: 0.16–0.52), across 235 globally distributed lakes between 1985 and 2009. This warming rate is consistent with the rapid annual average increase in air temperatures (0.25°C decade1) and ocean surface temperatures (0.12°C decade1) over a similar time period (1979–2012).
The Laurentian Great Lakes region and Northern Europe, lakes had significantly faster warming rate whereas the lakes in southeastern North America had significantly slower warming rate.
Ice covered lakes have surface water temperature increasing faster than air temperature. Due to the combination of shorter ice duration and rising air temperatures there is an earlier summer stratification that results in surface waters warming more rapidly.
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