April 7 (UPI) -- A rapid and dramatic transformation is underway in the Arctic Ocean. As warm waters flood Earth's smallest, shallowest ocean, portions of the Arctic are becoming increasingly similar to the Atlantic.
New research suggests the transformation is one of the main reasons why sea ice and ice sheets are in retreat in the Arctic.
Until recently, sea ice remained insulated from warm, salty Atlantic water by a thick layer of cold surface water. In recent years, that insulation has waned and warm Atlantic inflows have disrupted normal oceanic stratification and gained access to sea ice and the undersides of Arctic glaciers.
According to the latest research, detailed in the journal Science, the Arctic has become less stratified in recent decades. The average temperature difference between layers of Arctic Ocean waters is down by 2 degrees Fahrenheit.
"Previously this monster, Atlantic warm water, was well covered from the surface," study leader Igor Polyakov, an oceanographer at the University of Alaska, told Science. "The new data show this layer has disappeared in winter."
Researchers say the changes in temperature and composition in the Arctic are fueling a negative feedback loop resulting in further melting, mixing and homogenization -- further "Atlantification."
"Rapid changes in the eastern Arctic Ocean, which allow more heat from the ocean interior to reach the bottom of sea ice, are making it more sensitive to climate changes," Polyakov told Climate Central. "This is a big step toward the Arctic with seasonal sea-ice cover."
Since 2011, summers in the Arctic have been mostly ice-free. As researchers detailed in a separate study, the absence of ice has allowed sunlight to penetrate the Arctic surface, triggering larger, more prolific phytoplankton blooms.
"Both of our results show the Arctic becoming a very different place than it has been in the past," added Christopher Hovart, Harvard oceanographer and leader of the plankton study. "Water pathways are changing, the ecology is changing, all driven by the declining sea ice field."