Diminishing sea ice translates to the warmer ocean, more rain, and stronger trade winds

The Arctic and Antarctic ice loss will account for about one-fifth of the warming that is projected to happen in the tropics, according to a new study led by Mark England, a polar climate scientist at Scripps Institution of Oceanography at the University of California San Diego, and Lorenzo Polvani, the Maurice Ewing and J. Lamar Worzel Professor of Geophysics at Columbia Engineering, England's doctoral supervisor.

While there is a growing body of research showing how the loss of Arctic sea ice affects other parts of the planet, this study is the first to also consider the long-range effect of Antarctic sea ice melt, the research team said.

"We think this is a game-changer as it shows that ice loss at both poles is crucial to understanding future tropical climate change," England said of the study funded by NASA and the National Science Foundation. "Our study will open a hitherto unexplored direction and motivate the science community to study the large effects that Antarctic sea ice loss will have on the climate system." {module INSIDE STORY}

The years 2017 and 2018 set records for minimum sea ice extent in Antarctica. England and colleagues from Columbia University's School of Engineering, Colorado State University, and the National Center for Atmospheric Research in Colorado used supercomputer simulations to see what scenarios play out near the equator if that decline continues through the end of the century. They found that Antarctic sea ice loss combines with Arctic sea ice loss to create unusual wind patterns in the Pacific Ocean that will suppress the upward movement of deep cold ocean water. This will trigger surface ocean warming, especially in the eastern equatorial Pacific Ocean. Warming there is a well-known hallmark of the El Niño climate pattern that often brings intense rains to North and South America and droughts to Australia and other western Pacific countries.

As that surface ocean water warms, it will also create more precipitation. Overall, the researchers believe the ice loss at both poles will translate to a warming of the surface ocean of 0.5? (0.9?) at the equator and add more than 0.3 millimeters (0.01 inches) of rain per day in the same region.

This study joins several new analyses of the global impact of polar ice loss, including a January analysis by Scripps Oceanography physicist Charles Kennel suggesting that shrinking Arctic ice might change key characteristics of El Niño in the future.

Undetected cases, many of which were likely not severely symptomatic, were largely responsible for the rapid spread of the COVID-19 outbreak in China, according to new research by scientists at Columbia University Mailman School of Public Health. The findings based on a supercomputer model of the outbreak are published online in the journal Science.

The researchers report:

• 86 percent of all infections were undocumented prior to the January 23 Wuhan travel shutdown
• Per person, these undocumented infections were half (52 percent) as contagious as documented infections yet were the source of two-thirds of documented infections
• Government control efforts and population awareness have reduced the rate of spread of the virus in China; after travel restrictions and control measures were imposed, it spread less quickly {module INSIDE STORY}

"The explosion of COVID-19 cases in China was largely driven by individuals with mild, limited, or no symptoms who went undetected," says co-author Jeffrey Shaman, Ph.D., professor of environmental health sciences at Columbia University Mailman School. "Depending on their contagiousness and numbers, undetected cases can expose a far greater portion of the population to the virus than would otherwise occur. We find for COVID-19 in China these undetected infected individuals are numerous and contagious. These stealth transmissions will continue to present a major challenge to the containment of this outbreak going forward."

The researchers used a supercomputer model that draws on observations of reported infection and spread within China in conjunction with mobility data from January 10-23 and January 24-February 8. They caution that major changes to care-seeking or patient documentation practices, as well as rapid developments with regard to travel restrictions and control measures, may make predictions difficult.

"Heightened awareness of the outbreak, increased use of personal protective measures, and travel restriction have helped reduce the overall force of infection; however, it is unclear whether this reduction will be sufficient to fully stem the virus spread," says Shaman. "If the novel coronavirus follows the pattern of 2009 H1N1 pandemic influenza, it will also spread globally and become a fifth endemic coronavirus within the human population."