Home/BlogAs a followup to my cursory analysis suggesting increased precipitation was the probable cause of the record rise in Lake Superior water levels during 2013-2014, the GLERL folks pointed me to a relatively recent paper they published (Hydrologic Drivers of Record-Setting Water Level Rise on Earth’s Largest Lake System) which provides a detailed analysis of all of the hydrologic inputs and outputs to the levels of the separate Great Lakes (over-lake precipitation and evaporation, land precipitation runoff into the lake, river and channel inflows and outflows).
The following plot from their paper provides their statistically optimized estimates of the various hydrologic components that cause levels to change on Lake Superior. I suspect the most accurate measurements are the lake levels and outflow through the St. Marys River. Precipitation would be less well measured, and evaporation would be even more uncertain. Use the top portion to see the water level rise over the January 2013 thru December 2014 period, and use the bottom plot to understand the components that went into the rise, where arrows pointing up increase lake levels, and those pointing down decrease lake levels, compared to the long-term averages for those months (click on image for large version).
The bottom line is that the record rise in lake levels was mostly the result of above-normal precipitation (the blue [lake precip] and green [runoff from land precipitation] bars extending above the zero line). But also important was reduced evaporation (red bars) from the very cold winter of 2013-2014, which led to extensive ice cover and unusually cold lake water during the following summer.
Finally, note the grey bars, which indicate increased outflow through the St. Marys River at Sault Ste. Marie, MI, starting in mid-2013, which acted to limit the lake water rise.
As an aside, there is an interesting analogy between water storage in lakes, and heat storage in the ocean. There are inputs and outputs affecting each, and when there is a huge change (imbalance between inputs and outputs) it takes time for things to either depart from normal or go back to normal. Since the lake is small, that can happen in only a few years. In the case of heat storage in the ocean, it can take decades if not centuries for changes to be felt.
Typo in your title
wow…took me about 30 secs to see it. Amazing how the brain works.
Figure 8 is tough to figure.
the hydrologic gain and loss terms added together each month should result in the observed changes in water level, to within statistical uncertainty. I find the bottom portion of the plot easier to follow for the gain/loss terms…it gives the terms as departures from normal for that month. I use the upper portion just for the water level values.
Thanks, Dr. Roy.
Specifically, St Mary’s River outflow sounds like a volumetric figure. But the scale doesn’t reflect volumes. I’m not sure what the lower scale means
all flows and fluxes have been converted to equivalent water level change over the surface area of Lake Superior.
The lower scale are anomalies—departures from average for that calendar month — in meters equivalent of lake level change.
Upper scale is absolute departures of lake levels by month starting at zero in January 2013.
Hi Roy,
“In the case of heat storage in the ocean, it can take decades if not centuries for changes to be felt.”
Is pure conjecture?; when it has been observed many times that an La Nina event can follow a El Nino event the next year or vice-versa. What I understand is that it only takes a shift in the atmospheric circulation to produce one or the other events. And the atmosphere has no great thermal inertia relative to that of the oceans.
Do not worry about tomorrow when you have not yet solved today’s problems.
And it is often true that it is sometimes very difficult to see what should be obvious.
Have a good day, Jerry
Hi, Jerry, “And it is often true that it is sometimes very difficult to see what should be obvious.”
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A bigger problem for some than for others. ENSO is not ocean heat storage, not by any definition.
Have a good day.
yes, these *forcing* events can happen rapidly….just as a month of above-normal rainfall over the lake happens rapidly…but the ocean heat storage just sums up these events over time, and so it take a long time for any substantial changes in heat storage to occur. The “consensus” is that El Nino and La Nina event don’t even change the net heat content of the oceans…I don’t think this is necessarily the case.
Dr. Spencer, Bob Tisdale’s many prior discussions of ocean SST and heat content, especially as reflected in the ocean sub-basin numbers, arguably support the assertion that ENSO events do “change the net heat content of the oceans.”
I would appreciate your kind discussion of the reasons for your disagreement with the “consensus.”
Dave Fair
Excuse me for any confusion, I meant that I would like to know the reasons for your disagreement with the “consensus” that ENSO effects do not have any effect the net heat content of the oceans.
“…any effect…heat content”
Perhaps Dr Spencer means that a permanent regime of ENSO NEUTRAL – which is one of upwelling, anyway* – would be similar in the long run to the actual process of three regimes (NEUTRAL, EL NINO, and LA NINA).
*So not neutral in the sense of negligible, as regards what is going on in the water.
Precipitation would be less well measured, and evaporation would be even more uncertain.Boston Deck Pros