Climate change may be vastly underestimated due to ocean temperature miscalculations - study

Scientists have discovered a flaw in the method used to measure past ocean temperatures which, if correct, could mean we have underestimated the rate of climate change over the past 100 million years.

According to the current methodology, the temperature of the ocean depths, and the surface of the polar ocean, was some 15C (59F) higher 100 million years ago, compared to now.

These estimates have been challenged, however, by a joint team of researchers from the French National Center for Scientific Research (CNRS) and the Swiss Federal Institute of Technology in Lausanne (EPFL).

In their study, published in Nature Communications, the team posits that ocean temperatures may have remained relatively stable throughout this period, raising serious concerns about the current level of climate change being experienced by Mother Earth.

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“If we are right, our study challenges decades of paleoclimate research,” EPFL’s Anders Meibom said. “Oceans cover 70 percent of our planet. They play a key role in the Earth's climate. Knowing the extent to which their temperatures have varied over geological time is crucial if we are to gain a fuller understanding of how they behave and to predict the consequences of current climate change more accurately.”

Researchers believe that over the last 50 years certain processes used in current methodology were overlooked. Scientists have used foraminifera, which are tiny marine fossils found in the sediment cores extracted from the ocean floor, to calculate ocean temperatures.

This is done by calculating the levels of oxygen-18 content in the calcareous shells of foraminifera. The level of oxygen-18 is dependent on the temperature of the ocean in which the foraminifera live.

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The problem now, it seems, is that all of these estimates were based on the principle that the oxygen-18 content remained constant while the fossils were in the sediment. To test this theory, the team exposed the foraminifera to high temperatures in simulated seawater that only contained oxygen-18.

The results show that “the level of oxygen-18 present in the foraminifera tests can in fact change without leaving a visible trace, thereby challenging the reliability of their use as a thermometer.”

“What appeared to be perfectly preserved fossils are in fact not,” CNRS researcher Sylvain Bernard said. This basically means that previous estimates of ocean temperatures are simply incorrect and instead of showing the aforementioned 15C-degree drop over the last 100 million years, the study notes that “these measurements simply reflect the change in oxygen-18 content in the fossil foraminifera tests.”

“This change appears to be the result of a process called re-equilibration: during sedimentation, temperatures rise by 20 to 30C, causing the foraminifera tests to re-equilibrate with the surrounding water,” the study says.

But what next? Well, Meibom says scientists will now have to revisit the ocean's paleotemperatures and “carefully quantify this re-equilibration, which has been overlooked for too long.”

The researchers say that they will now focus on a number of other marine organisms to see if they can “clearly understand what took place in the sediment over geological time.”

 

Local fidelity key to ocean-wide recovery of humpback whales

Humpback whales can migrate thousands of miles to reach feeding grounds each year, but a new study concludes that their fidelity to certain local habitats -- as passed on through the generations -- and the protection of these habitats are key to understanding the ultimate recovery of this endangered species.

The study documents the local recruitment of whales in Glacier Bay and Icy Strait in Alaska over a 30-year period. The researchers found that contemporary whales that utilize these rich feeding grounds overwhelmingly are descendants of whales that previously used the area.

In other words, the population recovery of humpback whales in the region depends on cultural knowledge of migratory routes passed on from mothers to their calves; it is not a product of whales from outside the area suddenly "discovering" a rich feeding ground.

Results of the study are being published this week in the journal Endangered Species Research.

"Humpback whales are recovering from exploitation on an ocean-wide basis, but ultimately their individual success is on a much more local scale," said Scott Baker, associate director of the Marine Mammal Institute at Oregon State University and a co-author on the study.

"Humpback whales travel globally, but thrive locally."

The study compares records of individual whales returning to Glacier Bay. The first, referred to as the "founder's population," included whales documented by a local high school teacher, Charles Jurasz, beginning in the 1970s. Jurasz was one of the first researchers to realize that individual whales could be identified by photographs of natural markings -- a technique now widely used to study living whales.

Over the years, other researchers -- including the authors of this study -- continued to record the return of these whales by photo identification and they later collected small genetic samples to confirm the relatedness between individual whales.

Using a large database maintained by Glacier Bay National Park and the University of Alaska Southeast, the records of the founding population were then compared to records of the "contemporary population" returning to Glacier Bay, more than 30 years after Jurasz's initial studies. The results were striking.

Of the 25 "founding females" that were also sampled for genetic analysis, all but one was represented in the contemporary group -- either as still living, or by a direct descendant, or in many cases, both. Several of the founding females were even grandmothers of individuals in the contemporary population.

"We looked at three possibilities for population increase over a 33-year period including local recruitment from Glacier Bay/Icy Strait, recruitment from elsewhere in southeastern Alaska, and immigration from outside the region," said Sophie P. Pierszalowski, a master's student in OSU's Department of Fisheries and Wildlife and lead author on the study.

"It is clear that the contemporary generation of whales is based on local recruitment, highlighting the importance of protecting local habitat for recovering species, especially those with culturally inherited migratory destinations."

Humpback whales in the North Pacific were once estimated to number more than 15,000 individuals based on catch data before commercial whaling took a toll, reducing the population to less than a thousand by 1966. Humpback whales were first protected by the International Whaling Commission in 1965, then listed under the U.S. Endangered Species Act in 1973.

Since the protection, the oceanic population has increased to an estimated 21,000 individuals based on photo-identification studies and other evidence. The recovery has been slow, in part because humpback whales can live to be 70 years of age and their recovery is driven primarily by local fidelity and recruitment.

"Limiting vessel traffic in important habitats is one way to help protect humpback whales," Pierszalowski said, "along with maintaining legal distances by vessels, reducing the risk of entanglement with fishing gear, and maintaining stranding networks that have the capacity to quickly disentangle whales."

OSU's Marine Mammal Institute is based at the university's Hatfield Marine Science Center in Newport, Ore.

Eliminating Use of Plastic Bags is First Step in Cleaning Up Oceans

SAN JOSE – Activist Stuart Coleman, who led the effort to make Hawaii was the first U.S. state to eliminate using plastic bags in grocery stores, is emphasizing the need for greater efforts by civil society and the private sector to help “cure” the environment in Costa Rica and elsewhere.

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