Question: what causes el nino and whiteouts

Jessica Liley answered on 21 Nov 2013:

Oh I remember learning about El Nino’s in geography lessons!

An El Nino is a band of warm ocean water temperature which develops off the west coast of South America (in the east part of the Pacific Ocean). It’s part of what’s called the “El Nino Southern Oscillation” (ENSO) – this is the sea-saw pattern of changing air pressure between the east and west of the Pacific ocean (so, for example, high surface pressure in the east pacific, low surface pressure in the west, and the other way round too.)

– Firstly, in normal conditions the water at the surface of the ocean is warmer than the bottom of the ocean, because it’s heated by the sun. In the eastern Pacific, where South America is, the wind blows the water westwards (towards Indonesia) and the sun warms up the water even more as it travels. So now on the west Pacific, the sea level is much higher and warmer than in the East.

– As this happens, all the way over in the Eastern Pacific, something called “Upwelling” happens – when the cold water deep down in the bottom of the ocean moves to the surface and get’s heated up. This colder water is really nutrient rich so it’s great for supporting large fish populations. Fishermen in Peru have a great time!

BUT….

– In El Nino conditions… The warmer water from the Western pacific starts to move back towards the east, this makes the water temperature much warmer in the east, where South America is.

– This flattens out the sea surface again, and the water in the Eastern Pacific gets much hotter.

– Because this water is now so warm and deep in the east, many fish die because they can’t get the nutrients they need from the “Upwelling” (which I talked about above). “El Nino” means “Christ Child” – the fishermen from Peru call it this because they have such terrible fishing periods when El Nino’s occur!

I don’t know much about whiteouts, but I just had a little look on the internet – they happen when snow (or sand) reduce the visibility and the horizon disappears completely! It can happen either because of large amounts of snowfall, where there are blizzards and the snow reduces all visibility, or when you have thick fog at ground level which also stops all normal visibility. This February, America had one of the worst whiteouts in decades, 4,300 flights had to be cancelled! And unfortunately 7 people lost their lives too.