A common young-Earth creationist (YEC) argument for an Earth that is only 6000 or so years old is the “salty seawater” argument. The salty seawater argument, in its simplest form, states that one should be able to determine a maximum age for the oceans by measuring the rate at which various salts—such as the sodium in sodium chloride; and other metal ions—are entering the oceans and the rate at which they are being removed from the oceans, such as through sea spray, and calculating backwards to a time when there would have been no salt in the ocean.
I have pointed out some of the serious flaws with YEC reasoning on this one in my post Aluminum and the 100-year old oceans. Another Christian blog, Naturalis Historia, recently concluded a four-part series on the topic:
The third article in the series brought up an important point that has not been sufficiently highlighted by either advocates nor opponents of the YEC position, and that is the fact that there is absolutely no empirical evidence that seawater is indeed becoming saltier over time. There are seasonal and longer-term changes in ocean salinity from place to place, but these include both increases and decreases in salinity. In fact, given the current sparsity of salinity data and the three-dimensional and temporal variability of ionic concentrations in the oceans, we do not even precisely know how much of these ions, such as sodium ions, are in the oceans, nor can we tell whether their concentrations are increasing or decreasing.
If we did know the total quantities of various ions in seawater, I suspect we would discover that these values do vary over time. Some would be increasing, and some would be decreasing. For those that are increasing in concentration, it would be unwise to attempt to use them as geochronometers. The present rate of increase in the values would reflect only the current situation, which involves the present layout of the continents, climate, and human influences. There would be little reason to assume that the trends would have been identical a few hundred, a few thousand, or a few million years ago.
If the concentrations of some elements in seawater are found to be decreasing over time, it would be unwise to use these as geochronometers either. Using the same reasoning that YECs have used regarding ocean salinity, these would demonstrate that the ocean was created sometime in the future.
Over time, a number of faulty YEC arguments have drifted onto Answers in Genesis’s Arguments we don’t use page. Usually this has been the result not of careful YEC research, but of outside pressure that has forced them to admit that things like the “moon dust” and “vapor canopy” arguments do not work. The salty seawater argument does not work either, and should be added to this list.
Grace and Peace