Reefs in hot water

El Niño is blasting the tropical Pacific Ocean with record temperatures right now. Warm water, usually located far in the western Pacific, moves eastward during El Niño conditions, causing unusually high temperatures in the central and eastern Pacific. Two weeks from today, members of the Cohen Lab are heading out to the central Pacific to observe the impacts of El Niño on some of the most pristine and protected coral reefs in the world.

Map of sea surface temperature anomaly. Red colors indicate regions where the surface ocean 
is unusually warm right now, relative to conditions  typical for this time of year. 
Source: NOAA Coral Reef Watch

The exact cause of each El Niño event is hotly debated, but typically it begins with unusual wind patterns. In the tropics, the Trade Winds usually blow from the east, piling warm surface water into a "hill" in the western Pacific - but when those winds slacken, the pool of warm water flows back to the east, and El Niño sets in. Once El Niño is in place, changes in atmospheric circulation act to keep it in place, usually lasting 1-2 years.

Map of ocean "hotspots". Red colors indicate regions where the surface ocean
 is unusually warm right now, relative to the warmest month of the year in that location.
Source: NOAA Coral Reef Watch

Satellite image of Jarvis Island.

Impacts of El Niño are truly global. Southern California receives much needed rain, flooding occurs in Peru, and droughts strike Australia, just to name a few of the effects. Warm sea surface temperatures also impact coral reefs during El Niño. Some of the most pristine coral reefs are located in the central tropical Pacific, including the Pacific Remote Islands Marine National Monument - a group of 7 isolated corals islands and atolls that together form the largest network of marine protected areas in the world.

Some of these beautiful, pristine coral reefs are in the epicenter of El Niño warming. Jarvis Island, located just 20 miles south of the Equator is truly in the focal point of warm sea surface temperatures right now. The warmest temperatures around Jarvis measured since the beginning of the satellite era in 1982 occurred this week. 

Corals of Jarvis Island.
Photo credit US Fish and Wildlife Service

Two weeks from today, Cohen Lab members Tom DeCarlo, Hanny Rivera, Nathan Mollica, and Pat Lohmann, along with Tori Luu (Princeton) and Nadiera McCarthy (US Fish and Wildlife) are headed out to Jarvis Island aboard the 65' schooner Machias. No one has ever been to Jarvis during an El Niño. And there has never been an El Niño quite like this one. Can the corals handle the heat? Stay tuned to find out.

- Tom DeCarlo
MIT/WHOI Joint Program