Did the Sea of Galilee ice over 2,000 years ago?

Doron Nof, an oceanographer at Florida State University, offers an explanation for walking on water in the Sea of Galilee.

Doron Nof is no stranger to controversy. When you're applying modern scientific methods to stories from the Old and New Testaments, it just goes with the territory.

In 1992, Nof attempted to provide an oceanographic explanation for the biblical story of the Red Sea crossing by the ancient Israelites. More recently, the Florida State University oceanographer co-published a paper (click for PDF) that offered a paleolimnological explanation for walking on water in the Sea of Galilee.

Press reports reduced the substance of his research finding to a hot headline that --including a fair share of hate mail. But Nof was careful to avoid drawing any conclusion about the New Testament account that Jesus walked on water in Lake Kinneret (known outside of Israel as the Sea of Galilee). CNET News.com recently caught up with Nof to learn more about his findings.

Q: How were you and your colleagues able to recreate the conditions that prevailed in the Galilee region 2,000 years ago?
Nof: There is now a fairly standard oceanographic technique where you can go and take cores from the bottom of the ocean--in this case, the bottom of the Mediterranean--and you look at the sediments on the bottom and you take a core that is, say, 10 meters deep--or whatever it is--and you bring it up and you look at the shells that are inside that core. And you can tell the time by where you find (items) in the core. So, you can identify shells of different animals at each depth, and you can tell from what animals the temperature of the ocean was at that time.

If you look at these cores, you'll see that 2,600 years ago there was a dip in temperature of several degrees.

When you approached this question, what part of Lake Kinneret did you focus on?
Nof: Nobody drilled in the Kinneret, but people drilled in the Mediterranean, which is not that far and the air masses are very similar. We looked at some cores that were in the middle of the Mediterranean not far from Sicily...If you look at these cores, you'll see that 2,600 years ago there was a dip in temperature of several degrees. This is the temperature of the water in the Mediterranean. Now the heat capacity of water is much higher than the air. So for a drop of 4 degrees in the sea, there probably was a much larger drop in the atmosphere--at least as big.

You talk about this concept called "Springs Ice." Can you explain that?
Nof: If you look at the way that the usual river just spreads into the ocean, the river is fresh and the ocean is salty. So the river water is floating on top. That's why you see it from the air normally. With springs water it's the opposite situation: The lake is fresh and the spring is salty, so the water from the springs go to the bottom. It forms a plume on the bottom. The ice can only form above that plume--not on the entire lake. And the reason that it can form only above the plume is that the salty plume prevents convection.

When you cool fresh water from the top, usually what happens is that the water on the top gets heavier than the water below and it sinks to the bottom. So before you form ice on the top of a lake, you usually have to bring the entire lake down to fairly low temperatures.

In this particular case, you don't. The lower water can stay any temperature that it started with because nothing falls down to there. The cold temperature goes immediately to the formation of ice.

These days, the Sea of Galilee region is fairly warm. What was the average temperature during the time of Jesus?
Nof: It was probably maybe 10 degrees Fahrenheit lower than today, on average, according to these cores. I don't know how much it was. I'm telling you what we did, taking these cores to represent what happened above the Sea of Galilee.

Do you have an idea what the odds were of Springs Ice forming in Northern Israel back then?
Nof: All we know we can say about the Kinneret is because of what we did there. We took the temperature record in the last 20 years and from that record, you know, how it varies from day to day. And we lowered the mean of that record by that temperature difference that I mentioned to you. When we lowered the mean, we got a different record, a kind of a hypothetical record, and we consider that record to be representative of what the temperature above the lake was back at that time. And from that, we computed the likelihood that there will be ice.

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