In a brief discussion on the discovery that mega-scale icebergs once calved into the Arctic Ocean, Brian Thomas of the Institute for Creation Research posed the question: what causes an ice age in the first place? According to Mr. Thomas, the widespread evidence for much colder climates on Earth, during which massive continental ice sheets covered much of the northern hemisphere, is a “riddle” for conventional geologists. In a gross oversimplification of the problem, he reiterates a common speculation among young-Earth creationists:
The recipe for making an Ice Age calls for hot oceans and a colder atmosphere.
As it turns out, this statement is nearly half true. It doesn’t take a geologist to recognize that without a colder atmosphere, continental-scale glaciers could not persist. Glaciers can only grow if the mean annual temperature near their margins remains below freezing. Once the climate warms, for whatever reason, the edge of the glacier begins to melt and retreat. Once more land is exposed, vegetation grows back in place of the ice. Since dark-colored forests and soil absorb more solar radiation than a sheet of ice (which bounces it back into space like a giant mirror), glacial retreat causes the atmosphere to warm even faster. This positive feedback helps to explain how a two-mile-thick slab of ice could disappear within only a few hundred to a few thousand years. Conversely, it explains how ice-sheet growth can accelerate global cooling, since more ice cover means less energy absorbed.
But what do ‘hot oceans’ have to do with ice ages? Mr. Thomas tries to explain:
Oceans had to have heated fast enough to encourage extreme evaporation. Only then could enough water evaporate into the atmosphere where it would cool, and then fall on the continents and add to an ice sheet.
This so-called ‘extreme evaporation’ is not needed to supply moisture to high-latitude sites (e.g. northern Canada), where glacial ice sheets accumulate from snowfall. Even in winter, the air masses over the northern Pacific and North Atlantic oceans contain enough relative humidity to grant every child a coveted ‘snow day’. Whether that moisture falls over land depends rather on the structure of the wind currents (atmospheric circulation). Besides, whatever the temperature of the oceans, the atmosphere can hold a very limited amount of moisture. Extreme evaporation from ‘hot oceans’ would mainly result in massive rainfall over the sea.
On the other hand, Mr. Thomas accurately refers to an apparent paradox within paleoclimatology: as the ocean and atmosphere cool, less water will evaporate into the air, which should reduce the amount of precipitation. Given that Antarctica is one of the driest places on Earth, this concept is fairly intuitive. Within the conventional geological paradigm, therefore, how does one account for enough snow to cover Canada, Greenland, Scandinavia, and northern Siberia within millions of square miles of ice during the last ice age?
The answer lies in the rotation of the Earth and the modern configuration of the oceans and continents. Due to the Coriolis effect, both the Pacific and Atlantic oceans circulate in a clockwise fashion, delivering relatively cool waters to the Californian and west African coastlines, but relatively warm waters to eastern Asia/Alaska, Scandinavia, and the eastern U.S. seaboard:
So long as the Earth rotates about its axis and the tropical oceans receive a bulk of the sunlight, then relatively warm waters will continue to be driven to high latitudes off the coast of continents in the northern hemisphere. During winter, these warm waters tend to form areas of low atmospheric pressure in the northern oceans (the ‘subpolar lows’), resulting in counterclockwise or ‘cyclonic’ circulation. At lower latitudes, the relatively cool waters tend to form areas of high atmospheric pressure, resulting in clockwise or ‘anticyclonic’ circulation. Like a giant gear system, these pressure belts blow air masses from west to east, bringing regular storms deep into the continents:
There is no need, therefore, to make wild conjectures about about a catastrophic heat source during Noah’s flood to explain the source of ‘Ice Age’ snow. Geologists are not bothered by this riddle, because it doesn’t exist. Plenty of heat would have been available in the “well above freezing” oceans during the last glacial maximum, as indicated by numerous proxies for ocean temperature.
So what effect does global cooling have on atmospheric circulation? While this is a complicated question, climate models universally agree that cooling the Earth to levels seen during previous ice ages should increase the strength of jet stream circulation. The main reason is that in response to climate change, higher latitudes warm and cool faster than lower latitudes. In fact, we see this phenomenon today in reverse: global warming is far more evident in the Arctic region than in the tropics. Long-term cooling, therefore, would increase the temperature gradient from equator to pole, which exacerbates the pressure differences responsible for westerly air currents (i.e. west to east). As Earth plunged deeper into an ice age, the amount of moisture being delivered to high-latitude continental sites would have increased substantially, explaining the mass accumulation of ice sheets. The timing of these glacial-interglacial cycles, however, depends on external triggers, such as Milankovitch cycles.
Volcanic shades of nay
The global oceans are incredibly effective at tempering the atmosphere over the continents. If you have live near a coastline before, then you already know this well. Warm oceans lead to warmer air masses, which bring warmer temperatures downwind, even across the continent. As an example, the British Isles enjoy a much milder climate than central Canada, despite being at the same latitude. Siberian winters, on the other hand, are especially harsh, because ocean-born air masses are effectively blocked by local circulation patterns. If Brian Thomas believes that hot oceans existed after Noah’s flood, then he needs an additional mechanism to explain how Earth’s atmosphere could have been so cold at the same time. He writes:
Assuming a biblical timeline, massive amounts of volcanic activity took place during the Flood year and immediately afterward. The volcanic ash from these eruptions would have blocked out enough solar radiation to cool the atmosphere for hundreds of years after the Flood waters subsided—just what was needed to form the thick ice sheets that existed during the centuries-long ice age.
For the sake of discussion, let us grant that the Flood was accompanied by “massive amounts of volcanic activity”, which flooded the skies with ash. This ad hoc scenario invites two important questions. First, where is the evidence for such volcanic activity? Presumably, we should find anomalously large beds of ash interbedded with ice-aged sediments and ice cores, but we don’t. Additionally, we should be able to detect massive spikes in sulfur within speleothems and other cave deposits that presumably formed after the Flood, but we don’t. Volcanic ash layers do make an appearance in Quaternary deposits, but their distribution is too sparse and sporadic to explain some sort of ‘global winter’. Secondly, why does Mr. Thomas suppose that volcanic activity during the Flood would continue to impact temperatures for centuries? Ash and sulfur dioxide do not remain long in the atmosphere, but are short-lived pollutants. At best, his evidence-free conjecture could explain a few unpleasant summers, but nothing close to what is required for continental-scale ice sheets to grow from nothing.
On a final point, let us remember that the most recent ice age was merely one of dozens over the past few million years. Between these ice ages, Earth’s climate was as warm or warmer than today. These climate oscillations are evidenced especially well by long-term records of pollen, for example, which document the regrowth and recovery of warm-weather trees, herbs, and grasses between episodes of frozen tundra. In addition, the last ice age was not the most extensive. Glacial deposits indicate that some ice sheets grew as far as southern Siberia. Are we really to believe that these two-mile-thick sheets of ice advanced more than 1,500 miles from the Arctic coastline, then melted completely, grew back, melted completely, etc. at least a dozen times or more in only a few hundred years? Despite Mr. Thomas’s optimism and confidence, Flood geology provides no answers to the mysterious ice ages—only a new set of problems, which defy the laws of physics.