depth

The Threat From Thwaites | Earth Wise

January 20, 2022 By EarthWise Leave a Comment

The Thwaites Glacier in Antarctica is the widest glacier in the world. It is about 80 miles across and in places extends to a depth of about 2,600 to 3,900 feet. The glacier is roughly the size of Florida, and it currently contributes 4% of annual global sea level rise as it continues to retreat from a warming ocean.

The International Thwaites Glacier Collaboration is a team of nearly 100 scientists dedicated to studying the glacier. According to the scientists, Thwaites has doubled its outflow speed within the last 30 years. The glacier in its entirety holds enough water to raise global sea levels by over two feet, which would be catastrophic.

A third of the glacier flows more slowly than the rest because it is braced by a floating ice shelf that is held in place by an underwater mountain. The concern is that the brace of ice slowing the glacier may not last for long.

Beneath the surface, warmer ocean water is attacking the glacier from all angles. The water is melting the ice directly beneath the glacier causing it to lose its grip on the underwater mountain. Massive fractures have formed and are growing.

Warm water is also a threat for what is called the grounding zone, which is the area where the glacier lifts off the seabed. There are many possible scenarios under which there could be a major ice loss from the glacier. It is unclear how quickly it could occur. It might take decades, or it could be centuries. The threat is large enough and real enough that continued observation and research is essential.

**********

Web Links

The Threat from Thwaites: The Retreat of Antarctica’s Riskiest Glacier

Photo, posted October 16, 2012, courtesy of J. Yungel / NASA Ice via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Arctic Methane Starting To Release | Earth Wise

November 24, 2020 By EarthWise Leave a Comment

An international team of researchers has found evidence that frozen methane deposits in the Arctic Ocean have started to be released over a large area of the continental slope off the East Siberian coast. High levels of methane have been detected down to a depth of 1,100 feet in the Laptev Sea near Russia.

The slope sediments in the Arctic contain huge quantities of methane and other gases, known as hydrates. Methane has a warming effect 80 times stronger than carbon dioxide over a 20-year period. The US Geological Survey has identified Arctic hydrate destabilization as one of the four most serious scenarios for abrupt climate change.

The research team aboard a Russian ship said that most of the bubbles they observed coming up from the sea bottom were dissolving in the water, but that methane levels at the surface were four to eight times what would normally be expected.

Frozen methane deposits have been called the “sleeping giants of the carbon cycle.” If these deposit releases were to reach a high enough level, it would be a tipping point that could greatly increase the speed of global warming. With Arctic temperatures now rising more than twice as fast as the global average, the likelihood of a significant release of the frozen methane grows greater all the time.

Temperatures in Siberia were 9 degrees Fahrenheit higher than average from January to June this year. Last winter’s sea ice melted unusually early. This winter’s freeze has yet to begin, which is already a later start than any time on record.

These new discharges of methane are larger than anything found before and are a very worrisome occurrence.

**********

Web Links

Arctic methane deposits ‘starting to release’, scientists say

Photo, posted September 26, 2014, courtesy of the Office of Naval Research via Flickr. Photo credit: U.S. Navy photo by John F. Williams/Released.

Earth Wise is a production of WAMC Northeast Public Radio.

Even The Deep Sea Is Warming | Earth Wise

November 17, 2020 By EarthWise Leave a Comment

Approximately 75% of the area covered by ocean is deep, dark, and cold. This is known as the deep sea. But even in these remote regions of the planet things are heating up.

According to a new study published in the journal Geophysical Research Letters, researchers analyzed a decade of hourly temperature readings at four depths in the Atlantic Ocean’s Argentine Basin, off the coast of Uruguay. The research team selected recording depths that would best represent the average depth of the ocean, which is just over 12,000 feet.

The researchers found that deep sea temperatures fluctuate more than was previously known. They also detected a warming trend at the bottom of the ocean. In fact, all recordings indicated a warming trend of 0.02 to 0.04 degrees Celsius per decade between 2009 and 2019. This is a significant warming trend in the deep sea because temperature fluctuations are typically measured in thousandths of a degree.

Researchers say this increase is consistent with warming trends in the shallow ocean associated with anthropogenic climate change. However, they say more research is needed to better understand what is driving the warming temperatures in the deep sea.

A better understanding of what is driving these changes could have far-reaching implications. Since oceans absorb a significant amount of the world’s heat, learning about the oceans’ temperature trends could help researchers better understand temperature fluctuations in the atmosphere as well.

The researchers hope their findings will demonstrate the need to survey deep ocean temperatures annually in order to better identify the long-term trends.

**********

Web Links

The deep sea is slowly warming

Photo, posted July 1, 2018, courtesy of NOAA Ocean Exploration and Research via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Carbon In The Ocean | Earth Wise

October 13, 2020 By EarthWise Leave a Comment

New research from the University of Exeter in the UK reveals that the world’s oceans soak up more carbon than previously believed. Previous estimates of the movement of carbon between the atmosphere and the oceans did not account for the temperature differences between the water’s surface and a few meters below.

The new model includes this factor and finds that there is a significantly higher flux of carbon into the oceans.

The study calculated carbon dioxide fluxes from 1992 to 2018 and found that at certain times and locations there was up to twice as much CO2 contained in the ocean as determined from previous models.

The temperature differences between the surface of the ocean and the water at a depth of a few meters is important because the amount of carbon dioxide that can be absorbed in water depends very strongly on the temperature of the water. Anyone with a home soda maker knows this well as the devices always work much better with refrigerated water than room temperature water.

The difference in ocean carbon dioxide uptake measured from satellite data and calculated in the new modeling amounts to about 10% of global fossil fuel emissions, so it is a very significant revision. The revised estimate for carbon dioxide uptake actually agrees much better with an independent method for calculating the amount of carbon dioxide in the oceans. Those measurements came from a global ocean survey performed by research ships over decades.

Now that two so-called big data estimates of the ocean sink for CO₂agree pretty well, there is greater confidence that we understand this important aspect of the planet’s carbon cycle.

**********

Web Links

Ocean carbon uptake widely underestimated

Photo, posted December 30, 2012, courtesy of Jerome Decq via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Carbon And The Dark Ocean

January 4, 2018 By EarthWise Leave a Comment

Sunlight entering the water can travel as much as 3,000 feet into the ocean depths under the right conditions, but ordinarily there is no significant light that penetrates beyond about 650 feet down. That upper 650 feet is called the euphotic or “sunlight” zone and is home to most familiar marine life. The “dark ocean”, everything below that depth, makes up 90% of the ocean and remarkably little is known about it.