Maryland Coastal Bays

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Delmarva's Wet and Windy Weather - January 15, 2017

                If you have ever seen a weather map of Maryland, you might have noticed a division between the weather on the Western Shore and the Eastern Shore. It might be snowing in Baltimore, but in Salisbury and Ocean City it mostly rains. This change in weather from the mainland to the Delmarva Peninsula is due in part to the distance between the two shores, but also because of multiple unique environmental conditions.

                With the Atlantic Ocean and Coastal Bays on one side and the Chesapeake Bays on the other, the Delmarva Peninsula has many different environmental aspects. These aspects create unique local weather on Delmarva as opposed to the mainland. Wet, foggy, and windy conditions dominate our fall and winter seasons while the western shores of Virginia and Maryland get hit with snow, sleet, and freezing rain. The summer and spring seasons on the Eastern Shore tend to have more rain and higher humidity than the mainland; however, we tend to have cooler summers with fewer extremely high temperature days.

                Large bodies of water, such as the Chesapeake Bay and Atlantic Ocean, have a direct effect on temperatures and the local weather in coastal areas. Proximity to large bodies of water creates a buffer that stabilizes temperatures in the area, leading to less dramatic temperature fluctuations. This means that while inland regions can quickly decrease in temperature from fall to winter, coastal towns are kept warmer by the water’s effect on air. Water has a high heat capacity compared to both air and land. This higher heat capacity means that coastal towns and cities, like Ocean City, will experience warmer winters and cooler summer than inland areas as the surrounding water heats up and cools down slower than air and land.

                Shoreline communities also experience an interesting dynamic between the air over water and the air over land. Air tends to move from cooler areas towards warmer areas and the sun and season often dictates whether the land or water is cooler. During the day, the air onshore is warmer than the air over the water, so the wind usually blows from the water to the land. At night, the opposite occurs since the air over the water is warmer. Winds also tend to be stronger and more prevalent here on Delmarva as opposed to the mainland. This is because when wind travels over land there is more air resistance than over large bodies of water. Forests, buildings, hills, and mountains create air resistance which slows down or blocks wind on land, as opposed to bodies of water that create little to no air resistance until the wind meets the shore.

                Bodies of water not only affect how much precipitation a shoreline gets, but also what type of precipitation fall there. The Gulf of Mexico, for example, brings warm moist air over the Gulf Coast region, which results in thunderstorms, heavy rains, fog and, most notoriously, hurricanes. This severe precipitation occurs when the warmer, moist air collides with a mass of cooler, dry air. Here on the Eastern Shore we find that we generally tend to have more rain than the Western Shore. During the winter months when cold weather systems move across Maryland it might snow on the Western Shore but due to the heat capacity and evaporation from the Chesapeake Bay and Atlantic Ocean, the same weather system will most likely produce rain for the Delmarva Peninsula.

                The direction of oceanic currents also greatly affects the climate of coastal towns and areas. The Gulf Stream brings warmer water from the Caribbean upward along the United States’ Atlantic coast. The Gulf Stream brings slightly warmer water to the Atlantic coastal states, which can lead to more precipitation, but is also a possible pathway of hurricanes and tropical storms. These storm systems move from the Caribbean or west coast of Africa toward North and South America, often making landfall near the Florida peninsula and Gulf of Mexico. Hurricanes and tropical storms can gain strength, size, and heavier precipitation from warm water; the Gulf Stream can help fuel a hurricane making them more powerful and dangerous to the states in their path. Since 2004, scientists have seen a reduction in flow speed of the Gulf Stream along the Atlantic coast. While not dramatic, this slower flow speed has been attributed as one of the reasons for higher sea-level rise along the Atlantic. Normally, the Gulf Stream helps to pull water away from the shore. Due to climate change and the addition of more fresh water into the ocean, currents such as the Gulf Stream are slowed. This means that the Gulf Stream no longer pulls as much water away from the coasts as it would normally, resulting in an increase in sea-level rise due to a higher water volume in the coastal areas.

                Delmarva’s unique weather and location has allowed the creation of an amazing diversity of ecosystems, animals, and plants. Unfortunately, if current trends continue, there will eventually be shifts in our global climate that will change our weather patterns, creating change in our local ecosystems that could be irreversible.

Harrison Jackson is the former Education Coordinator for the Maryland Coastal Bays Program and current graduate student at Clemson University.



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