Getaway Islands

Summer is here and for many people it's the perfect time to relax at the beach. If you're at an East Coast beach, odds are you're on a barrier island. The Atlantic barrier islands extend from Canada to Florida, then up Florida's Gulf Coast and all the way around to Mexico. Prior to development, many of these islands came and went at the whims of the tides and storms. Now that we've built homes and resorts on them, there is a vested interest to make them more permanent by using jetties to block the outflow of sand and beach replenishment to restore what's been lost. Let's take a look at the natural history of where you built that sand castle.

Grassy dune in New Jersey

Barrier islands, if left to nature, live and die by the tides. Ocean currents carry sand away from the islands. The sand either moves out to the sea floor, where it can be brought back to the island by currents, or it is carried to another part of the island or to a different island. Strong storms can accelerate the process, wiping islands off the map or opening up a new inlet to the back bay.

Hurricane Irene cut these inlets across Hatteras Island (NOAA) 

Barrier islands can move toward the mainland as wind blows sand over the dunes to the bay side. The marshes fill in with sand and build up new dunes, while ocean moves to where the dunes originally were and new marshes form in the bay on the edge of the old marshes.

Salt marsh at Assateague Island (NPS)

The islands are important because they are barriers protecting the mainland from such storms. A few weeks ago we looked at hurricanes on this blog. Barrier islands absorb the brunt of the storm surge that comes in ahead of the hurricane. Developed barrier islands still absorb the storm surge, but not as well as undeveloped islands from times past. Impermeable surfaces like roads and parking are terrible at absorbing water, while sand drains quickly. If the dunes have been removed from an island, the storm surge rushes right over top with nothing but buildings to slow it down.
Barrier islands are also important as habitat for critters other than summer vacationers. On an undeveloped island, different plants and animals that can tolerate different amounts of salt water and exposure to the air make their homes in different zones. Clams live beneath the sandy shore, while birds that prey on them scurry above. Grasses hold the dunes in place, and at the highest points of the island you can find trees and shrubs where songbirds and mammals live. Brackish marshes on the other side of the dunes host crabs and serve as a nursery where fish can eat and grow before venturing into the open sea. Wading shorebirds take advantage of this bounty. Beyond the marsh is the back bay and the mainland.

Ghost crab (NPS)

Sandpiper feeding frenzy

The US has more barrier islands than any other country in the world. Best known are New York's Fire Island, Texas's South Padre Island, the Outer Banks of North Carolina, and the Jersey Shore. If you spend a summer weekend at the beach, be sure to check out the wild side of things.
This week's information comes from Science News for Students.

Hurricane!

With the beginning of June, the northern Atlantic is officially in hurricane season. Tens of millions of people along the East , and in Central America and the Caribbean are at risk from these monster storms annually. Let's have a look at where they come from.

Hurricane! (NOAA)

Hurricanes begin as a low pressure system that gains strength from warm ocean water in or near the tropics. The air moving in to the low pressure area rises, cools, and condenses into clouds. The low pressure continues to draw in more air, and the system begins spinning and forms an eye.

Hurricane formation (NASA)

Wind speeds increase as the storm grows. Despite winds that can exceed 150 miles per hour, most damage is caused by water. As the hurricane approaches land, the wind pushes the water ahead of it. This is called the storm surge. Once the hurricane makes landfall it rapidly loses strength without the warm ocean beneath it. As it moves along, it dumps tremendous amounts of rain, which can cause catastrophic flooding.

Where hurricanes form (NASA)

Thanks to the miracle of satellite radar, we know well in advance of when and where hurricanes will strike. If you are in a hurricane area and are earned to evacuate, please do. Information came from NASA this week.

Gone With The Wind

It rustles. It rocks us to sleep. It kicks up the surf. It whispers, howls, and screams like the banshees. This week we're talking about the wind. Where does it come from?
On a basic level, the wind is just air moving. But why? Osmosis- air moves from areas of high pressure to areas of low pressure. You can test this yourself by blowing up a balloon, then letting go of the open end. Inside the balloon is more compact. The pressure of the incoming air presses against the balloon, making it expand. Once you let it open the high pressure air rushed out to where there is less pressure.

Low pressure following warm air (NOAA)

So what causes the pressure differences? Temperatures.
Warmer air rises and the molecules spread out. That motion causes an area of low pressure that other air moves in to fill, and we feel that as wind. Storms can cause greater differences in pressure, which leads to higher wind speeds. Hurricanes have extremely low pressure, which explains why they have such strong wind. here.

Wind moving in to fill a void left by warm air rising (NOAA)

Tornados are a whole other ball of wax, which we talked about
Now you know the science behind the wind. Next time it rattles your house or flies your life you'll have a greater understanding of what's going on.
This week's information comes from NOAA.