Tag Archives: Climate

Godzilla El Niño and You

You’ve probably heard a lot about this year’s El Niño, which is predicted to be the biggest since 1998. What exactly does that mean? This global weather phenomenon has complex and far-reaching consequences, but the mechanism behind it is simple!

ThermoclineCupsLet’s start by considering normal weather patterns in the Pacific ocean. Water near the surface is heated by the sun. This warm upper layer floats on top of cooler, denser ocean depths, resulting in a dramatic temperature barrier called the thermocline. At left, we’ve modeled the thermocline in a plastic container: warm water is colored red, and cool water is colored blue. Because the warm water is less dense, it floats.

In a non-El-Niño year, equatorial trade winds blow strongly from east to west, moving surface water along with them. In the Pacific, these winds push the warm upper layer of the ocean towards Australasia. Cooler water wells up in the east to fill the space left by the warm water moving out. As a result, the thermocline sits at a slant. Surface temperatures are normally warmer in Indonesia than Ecuador by about 45 degrees Fahrenheit.

This tilt in the thermocline is responsible for the typically wet climate in Southeast Asia and relatively dry conditions along the Americas’ equatorial Pacific coast. Warm water near southeast Asia and Australia evaporates and blows inland, resulting in lots of rain. Cool, nutrient-rich water from deep in the ocean sustains whole ecosystems in the eastern Pacific, but doesn’t generate much precipitation.

ThermoclineGIF

During an El Niño year, the thermocline shifts, resulting in warmer than normal surface temperatures in the eastern tropical Pacific. Animation credit: NASA Goddard

In an El Niño year, trade winds weaken. With nothing to hold it in place, warm surface water sloshes eastward towards the Americas, leaving the western Pacific cooler than normal. Australia and southeast Asia experience drought conditions. The equatorial Americas see unusually intense precipitation, which comes in the form of coastal flooding in some regions and severe winters in others. Since warm water doesn’t vacate the eastern ocean, cool water can’t well up to replace it. Coastal ecosystems that depend on deep-ocean nitrates and phosphates struggle, undermining economies that depend on industrial fishing.

El Niño is defined as unusually warm surface water in the eastern tropical Pacific, but its consequences extend around the world. North of the equator, the western U.S. sees intense winter storms. Across the ocean, unseasonably dry weather disrupts agriculture in Indonesia, Australia, and even South Africa.

Although the thermocline’s oscillation isn’t precisely predictable, it is part of an ocean temperature cycle that repeats every two to seven years. So, yes, it’s going to be an intense season! That said, this is nothing that hasn’t happened before, and we’ll likely see a new “Godzilla” El Niño in another decade or a few.

Written by: Scott Alton, Caela Barry

Geyser in a Bottle! Science!!!

Ever wish you could control the weather? In this experiment, we’ll harness the weight of the atmosphere to make a tiny storm in a beaker! As you read this sentence, the air around you is exerting enormous pressure on your body. Imagine a jacket made of one-inch checkerboard squares. Now imagine that each tiny box weighs fifteen pounds! At sea level, atmospheric pressure is about 15 pounds per square inch. Multiply 15 by the number of square inches on the surface of your body to get an idea of how much weight you’re bearing every moment of every day.

WaterGeyser1

Atmospheric pressure results from the weight of the air above you. Credit: Peter Mulroy, http://peter-mulroy.squarespace.com/air-pressure/

We don’t notice all this weight because we’re used to it. Take the pressure away, though, and awesome dynamics ensue. Heating a volume of air is one way to create a drop in pressure. Adding heat to a gas causes its molecules to speed up and spread out.

WaterGeyser2

As the air inside the flask expands, some is pushed out through the tube. Invert the container into cool water and the liquid blocks the opening– the escaped air is trapped outside! The gas left inside the flask shrinks as it cools, creating a low-pressure zone in the container. Here’s where that 15 pounds per square inch comes in. Once the pressure in the flask is lowered, atmospheric pressure pushing on the surface of the water outside forces the liquid up the tube.

WaterGeyser3
When the water reaches the main compartment of the container, the gas inside experiences a sudden drop in temperature. A chain reaction of cooling occurs, and water rushes in to fill the empty space left by the condensing air.

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