Earth Design Update: Sea-Salt Aerosols

Ten American scientists have strengthened the case for divine design of Earth and for the reliability of Scripture, though they may not realize they have done so. Their experiments tell us, first, that the interface between Earth’s oceans and atmosphere perfectly fits life’s needs for relatively moderate temperatures and a stable water cycle. Second, their findings offer possible help in understanding what happened on the fourth creation day, when Earth’s atmosphere changed from translucent (opaque) to transparent.

These researchers studied aerosols, particles suspended in air, above the oceans in the southern hemisphere. They focused specifically on intermediate-sized (0.08-1.0 micrometers) aerosols, the ones that 1) most efficiently scatter solar radiation, and thus balance Earth’s surface temperatures, and 2) serve as the tiny “seeds” around which water drops, then clouds, and finally rain drops form, producing Earth’s water cycle. They chose the southern oceans (40-50° S) where the boundary between the ocean and the atmosphere is relatively undisturbed by continents.

Their study showed that over 90% of the aerosols in this region falling within the crucial intermediate size range are grains of sea salt. These sea salt aerosols are there because of a “just right” balance between ocean salinity and wind velocity at the ocean’s surface. In other words, for Earth to end up with a life-suitable surface temperature range, climate, and water cycle appropriate for advanced life, five Earth features (among others) require fine tuning:

• Earth’s rotation rate, which determines surface wind velocities, must fall within a certain range,
• Earth’s continents must be distributed in a such a way as to allow for strong and steady winds over large areas (such as the “roaring forties”),
• Ocean salinity must fall within a certain range
• the salt cycle (circulation of salt from the continents to the oceans and back again) must proceed at an adequate rate, and
• atmospheric composition must be just right to hold the aerosols long enough for water drops to form around them.

Understanding more about sea-salt aerosols today may help us understand a dramatic change that occurred in Earth’s distant past, a transformation described in Genesis 1:14-15, creation day four. Earth’s atmosphere changed at that time from being a permanent, thick overcast to being occasionally transparent. Since Earth was rotating three or four times faster in that early era than it does today, and since the continents were less widely dispersed to break up the surface wind, sea-salt aerosols were likely much more abundant then than they are now.

More sea salt whipped into the atmosphere meant a heavier (much heavier) cloud cover until the continents spread and the rotation slowed. At some point these two factors (along with the reduction of carbon dioxide in the atmosphere and increase of oxygen resulting from plant life) reached the right levels to bring about a significant decrease in that cloud cover, yet still adequate to produce rainfall. At that time, an observer on the surface (where God says His Spirit was hovering) would see, for the first time, the heavenly lights, our sun, moon, and stars.

Reference:
D. M. Murphy, et al, “Influence of Sea-Salt on Aerosol Radiative Properties in the Southern Ocean Marine Boundary Layer,” Nature, 392 (1998), pp. 62-65.