Cycles in the growth and decay of Antarctica's ice sheets once shaped marine biological productivity thousands of miles away in the subtropical ocean, according to new research led by scientists at the University of Wisconsin-Madison. The study, published in the Proceedings of the National Academy o f Sciences, found that the obliquity cycle—a 40,000-year astronomical cycle tied to changes in Earth's axial tilt—influenced ocean productivity in subtropical latitudes about 34 million years ago, when the Antarctic ice sheet was first expanding. ...read more read less