Significant Sea-Level Changes Causing Changes in Ocean Chemistry Surprises Researchers

Tracking the climate conditions of the past helps researchers understand the present state of affairs in terms of the environment. In a recent study, experts focused on a period from 15 million to 6 million years ago when significant sea-level changes occurred, stated Live Science. Findings regarding the event have been published in the Geochemistry, Geophysics, Geosystems journal. 

Past examinations of the sea floor's magnetic pattern have confirmed that during this period, ocean crust production went down by 35%. Researchers believe this phenomenon was facilitated because of a global slowdown that happened in seafloor spreading. This further led to the deepening of ocean basins. The study took into consideration factors like crust destruction rates, the age of the ocean crust, as well as conditions of the time, and concluded that the phenomenon must have resulted in the plummeting of sea level.

The study utilized math and models to understand how the 'area-age distribution' of the seafloor changed with time. They started with a present-day seafloor age map and altered the crust production based on the 35% slowdown that happened 15 million to 6 million years ago. Thereafter, the experts took two models, the Plate Cooling Model and the Half-Space cooling model. The team also calculated the different ways in which the crust could get destroyed over the years. Real-world data from sediment layers from coastal New Jersey and offshore Nova Scotia was also incorporated into the examination. The results indicated that the sea level was reduced by 26–32 meters during that period.

Researchers also think the sea level's plummeting and the spreading of the sea floor could have forever changed the ocean's chemistry. This may be because the heat that typically passed from the hot mantle to the ocean fell by about 8%. There was an even greater decrease in hydrothermal flux near the oceanic ridges. Experts estimated that the fall here must have been around 35%.

The slowdown of Earth's crust production could also lead to decreased volcanic emissions of greenhouse gases. This would facilitate global cooling and falling of sea level by more than 60 additional meters. This is because of the thermal contraction of seawater and the trapping of water in continental ice sheets. Researchers also noted that there was a 'slower spreading' happening at the ridges compared to other areas, which could have caused thinner crusts. This kind of crust sinks more, leading to another two-metre fall in sea level. 

The study is valuable because only some evidence regarding sea level changes over the past 15 million years through coastal rock layers is available to researchers. Experts further added that these new results align with how experts interpreted existing sequence stratigraphy data gathered from coastal New Jersey and offshore Nova Scotia. Another noteworthy aspect of this phenomenon is that if the East Antarctic Ice Sheet (Earth's largest ice sheet) undergoes complete melting, the impact that the sea level would experience will be the same, 26 to 32 meters, but in the opposite direction.