The Upper Ocean — a collection of articles from the Encyclopedia of Ocean Sciences, 2nd Edition — reflects the trend toward the interdisciplinary study of oceanography, which integrates the disciplines of biology, chemistry, geology and physics. The upper ocean’s contact with the atmosphere profoundly impacts climate, making this reference both timely and critical. The selection of articles — all written by experts in their field — focuses on Air-Sea Transfers; Air-Sea Chemical Exchanges and Cycles; The Sea Surface, Waves and Upper Ocean Processes; Upper Ocean Circulation and Structure; Plankton; Ice; and Measurement Techniques including Remote Sensing.