Antarctic Sea Ice Near Historic Lows; Arctic Ice Continues Decline - EARTH

Sea ice at both the top and bottom of the planet continued its decline in 2024. In the waters around Antarctica, ice coverage shrank to near-historic lows for the third year in a row. The recurring loss hints at a long-term shift in conditions in the Southern Ocean, likely resulting from global climate change, according to scientists at NASA and the National Snow and Ice Data Center. Meanwhile, the 46-year trend of shrinking and thinning ice in the Arctic Ocean shows no sign of reversing.

“Sea ice acts like a buffer between the ocean and the atmosphere,” said ice scientist Linette Boisvert of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Sea ice prevents much of the exchange of heat and moisture from the relatively warm ocean to the atmosphere above it.”

Less ice coverage allows the ocean to warm the atmosphere over the poles, leading to more ice melting in a vicious cycle of rising temperatures.

Historically, the area of sea ice surrounding the Antarctic continent has fluctuated dramatically from year to year while averages over decades have been relatively stable. In recent years, though, sea ice cover around Antarctica has plummeted.

On Feb. 20, 2024, Antarctic sea ice officially reached its minimum extent for the year. This cycle of growth and melting occurs every year, with the ice reaching its smallest size during the Southern Hemisphere’s summer. According to the National Snow and Ice Data Center, this marks the second-lowest sea ice extent recorded by satellites, reflecting a trend of declining coverage over time.
Credit: NASA’s Goddard Space Flight Center/Scientific Visualization Studio
Download this video in HD formats from https://svs.gsfc.nasa.gov/14538.

“In 2016, we saw what some people are calling a regime shift,” said sea ice scientist Walt Meier of the National Snow and Ice Data Center at the University of Colorado, Boulder. “The Antarctic sea ice coverage dropped and has largely remained lower than normal. Over the past seven years, we’ve had three record lows.”

This year, Antarctic sea ice reached its lowest annual extent on Feb. 20 with a total of 768,000 square miles (1.99 million square kilometers). That’s 30% below the 1981 to 2010 end-of-summer average. The difference in ice cover spans an area about the size of Texas. Sea ice extent is defined as the total area of the ocean in which the ice cover fraction is at least 15%.

This year’s minimum is tied with February 2022 for the second lowest ice coverage around the Antarctic and close to the 2023 all-time low of 691,000 square miles (1.79 million square kilometers). With the latest ice retreat, this year marks the lowest three-year average for ice coverage observed around the Antarctic continent across more than four decades.

The changes were observed in data collected with microwave sensors aboard the Nimbus-7 satellite, jointly operated by NASA and the National Oceanic and Atmospheric Administration (NOAA), along with satellites in the Defense Meteorological Satellite Program.

NASA’s Earth Observatory: Antarctic Sea Ice at Near-Historic Lows

Meanwhile, at the other end of the planet, the maximum winter ice coverage in the Arctic Ocean is consistent with an ongoing 46-year decline. Satellite images reveal that the total area of the Arctic Ocean covered in sea ice reached 6 million square miles (15.65 million square kilometers) on March 14. That’s 247,000 square miles (640,000 square kilometers) less ice than the average between 1981 and 2010. Overall, the maximum winter ice coverage in the Arctic has shrunk by an area equivalent to the size of Alaska since 1979.

This year’s Arctic ice maximum is the 14th lowest on record. Complex weather patterns make it difficult to predict what will happen in any given year.

The Arctic Ocean sea ice reached its annual maximum on March 14, continuing the long-term decline in ice at the poles.

Chart by Lauren Dauphin/NASA Earth Observatory, using data from the National Snow and Ice Data Center.

Shrinking ice makes Earth more susceptible to solar heating. “The sea ice and the snow on top of it are very reflective,” Boisvert said. “In the summer, if we have more sea ice, it reflects the Sun’s radiation and helps keep the planet cooler.”

On the other hand, the exposed ocean is darker and readily absorbs solar radiation, capturing and retaining that energy and ultimately contributing to warming in the planet’s oceans and atmosphere. 

Sea ice around the poles is more susceptible to the weather than it was a dozen years ago. Ice thickness measurements collected with laser altimeters aboard NASA’s ICESat-2 satellite show that less ice has managed to stick around through the warmer months. This means new ice must form from scratch each year, rather than building on old ice to make thicker layers. Thinner ice, in turn, is more prone to melting than multi-year accumulations.

“The thought is that in a couple of decades, we’re going to have these essentially ice-free summers,” Boisvert said, with ice coverage reduced below 400,000 square miles (1 million square kilometers) and most of the Arctic Ocean exposed to the Sun’s warming glare.

It’s too soon to know whether recent sea ice lows at the South Pole point to a long-term change rather than a statistical fluctuation, but Meier believes long term declines are inevitable.

“It’s only a matter of time,” he said. “After six, seven, eight years, it’s starting to look like maybe it’s happening. It’s just a question of whether there’s enough data to say for sure.”

Reference: NSIDC Sea Ice Index Daily and Monthly Image Viewer

By James Riordon
NASA’s Earth Science News Team 

Source: Antarctic Sea Ice Near Historic Lows; Arctic Ice Continues Decline - NASA

Wilson's disease

 

A brown ring on the edge of the iris (Kayser–Fleischer ring) is common in Wilson's disease, especially when neurological symptoms are present.

Not to be confused with Wilson's temperature syndrome, an alternative medicine concept.

Wilson's disease is a genetic disorder in which excess copper builds up in the body. Symptoms are typically related to the brain and liver. Liver-related symptoms include vomiting, weakness, fluid build-up in the abdomen, swelling of the legs, yellowish skin, and itchiness. Brain-related symptoms include tremors, muscle stiffness, trouble in speaking, personality changes, anxiety, and psychosis.^[1]

Wilson's disease is caused by a mutation in the Wilson disease protein (ATP7B) gene. This protein transports excess copper into bile, where it is excreted in waste products. The condition is autosomal recessive; for people to be affected, they must inherit a mutated copy of the gene from both parents. Diagnosis may be difficult and often involves a combination of blood tests, urine tests and a liver biopsy. Genetic testing may be used to screen family members of those affected.^[1]

Wilson's disease is typically treated with dietary changes and medication. Dietary changes involve eating a low-copper diet and not using copper cookware. Medications used include chelating agents, such as trientine and D-penicillamine, and zinc supplements. Complications of Wilson's disease can include liver failure, and kidney problems. A liver transplant may be helpful to those for whom other treatments are not effective or if liver failure occurs.^[1]

Wilson's disease occurs in about one in 30,000 people.^[1] Symptoms usually begin between the ages of 5 and 35 years.^[1] It was first described in 1854 by German pathologist Friedrich Theodor von Frerichs and is named after British neurologist Samuel Wilson.^[4] 

Signs and symptoms

The main sites of copper accumulation are the liver and the brain, and consequently liver disease and neuropsychiatric symptoms are the main features that lead to diagnosis.^[5] People with liver problems tend to come for medical attention earlier, generally as children or teenagers, than those with neurological and psychiatric symptoms, who tend to be in their 20s or older. Some are identified only because relatives have been diagnosed with Wilson's disease; many of these, when tested, turn out to have been experiencing symptoms of the condition, but have not received a diagnosis.^[6]

Neuropsychiatric symptoms

About half of the people with Wilson's disease have neurological or psychiatric symptoms. Most initially have mild cognitive deterioration and clumsiness, as well as changes in behavior. Specific neurological symptoms usually then follow, often in the form of parkinsonism (cogwheel rigidity, bradykinesia, or slowed movements and a lack of balance are the most common parkinsonian features^[8]) with or without a typical hand tremor, masked facial expressions, slurred speech, ataxia (lack of coordination), or dystonia (twisting and repetitive movements of part of the body). Seizures and migraine appear to be more common in Wilson's disease.^[5] A characteristic tremor described as "wing-beating tremor" is encountered in many people with Wilson's; this is absent at rest but can be provoked by abducting the arms and flexing the elbows toward the midline.^[9]

Cognition can also be affected in Wilson's disease, in two, not mutually exclusive, categories - frontal lobe disorder (may present as impulsivity, impaired judgement, promiscuity, apathy, and executive dysfunction with poor planning and decision-making) and subcortical dementia (may present as slow thinking, memory loss, and executive dysfunction, without signs of aphasia, apraxia, or agnosia). These cognitive involvements are thought to be related and closely linked to psychiatric manifestations of the disease.^[8]

Psychiatric problems due to Wilson's disease may include behavioral changes, depression, anxiety disorders, and psychosis.^[5] Psychiatric symptoms are commonly seen in conjunction with neurological symptoms and are rarely manifested on their own. These symptoms are often poorly defined and can sometimes be attributed to other causes. Because of this, diagnosis of Wilson's disease is rarely made when only psychiatric symptoms are present.^[8] 

For more information

From Wikipedia, the free encyclopedia

Source: Wilson's disease - Wikipedia