Navigation:
Supported By:

NC COHAZ GLOSSARY

Anoxia            Anoxia is a condition in which there is no dissolved oxygen in a body of water, and anoxia results in the death of oxygen-dependent species in that body of water.

Dissolved Oxygen            In water, oxygen is dissolved in order to sustain life.  The oxygen in the water may become depleted or reduce resulting in the conditions of anoxia and hypoxia which can result in the degradation of the ecosystem and a mass loss of life.

Dune Blowout            A dune blowout occurs when a dune is breached by forces such as crashing waves, rising sea level causing erosion of the dune, or by winds redistributing the sand.  Blowouts result in the loss of protection of inland habitats allowing for the ocean to flood the area.

Dune Blowout-False Cape State Park, VA: http://farm1.static.flickr.com/135/379887363_a07d6e6ff2.jpg?v=0.

Erosion            Erosion is the displacement of sediments, such as sand, due to natural processes (i.e., wind, water displacement and transport).  Erosion occurs most dramatically during severe coastal storms such as hurricanes and Nor’easters.  Three types of erosion are acute, chronic, and seasonal.

           

Erosion in Nags Head after a Coastal Storm: http://www.daylife.com/photo/0e844u8g7Q6jC.

Estuary           Estuaries are semi-enclosed bodies of water where salt water from the Ocean meets with freshwater draining from rivers and streams.  In North Carolina, The Cashie, Chowan, and Roanoke Rivers converge to form the Albemarle Sound.  The Neuse, Tar/Pamlico, and Pungo Rivers converge to form the Pamlico Sound.  The area covered by the Albemarle, Croatan, Currituck, Pamlico, and Roanoke Sounds form the Albemarle-Pamlico Estuarine System.  Geologically, estuaries can be divided based upon physical features into four categories: bar-built, drowned river valleys, fjords, or tectonic.  The Albemarle-Pamlico represents a combination of a drowned river valleys and a bar-built systems.  In drowned river valleys such as the Roanoke/Albemarle Valley Fill water from sea level rise flooded valleys carved out by rivers.  The Alligator, Cashie, Chowan, Pasquotank, Perquimans, and Roanoke Rivers all contribute to the freshwater input of water into the Albemarle Sound.  In bar-built estuaries such as the Dare Submarine Headland (area covered by the northern extent of the Pamlico Sound) water flow is restricted by barrier islands, sand spits, and sand bars.  Water flows in and out of the ocean through inlets in the sand.  In the Albemarle-Pamlico the inlets maintaining water flow are Beaufort Inlet, Hatteras Inlet, Ocracoke Inlet, and Oregon Inlet.  In terms of circulation, estuaries are commonly divided into three categories: partially mixed, well mixed, and salt wedge. The Albemarle Sound is considered a salt-wedge estuary due to the large input of freshwater from rivers dominating the basin.  Due to this, there is little salt water in the Albemarle, but rather fresh and brackish.  The Pamlico Sound is an example of a partially mixed estuary.  In the Pamlico Sound, water from the Atlantic flows inward at inlets in the Outer Banks mixing with water from the Tar/Pamlico and Neuse Rivers.  The large tidal input creates an upstream underwater current and weaker river input creates downstream flow.  Where the two meet, a shoal is created and between the shoal and inlets there is stratification where salinity increases from freshwater at the surface to saltier water deeper in the water column.  Due to the salinity change with distance from the ocean, there is a vast diversity of ecosystems and organisms in and around the Albemarle-Pamlico.   

Satellite image of the Albemarle-Pamlico Estuarine System in North Carolina: http://sitemason.vanderbilt.edu/files/cjR6j6/unitedstates_2003365_lrg.jpg/main.jpg.

Fetch           Fetch is the distance or area over which wind blows.  The length or overall size of the fetch is directly proportional to the size of waves which can be generated.  If the wind is of a high speed and the distance of water which it travels is rather large, large waves can be produced.  On the contrary, calmer winds which travel over short distances would produce little wave activity.  For example, due to the relative size of the Chesapeake Bay, moderate sized waves can be created depending upon wind conditions.

Tug and barge - Chesapeake Bay

Waves in the Chesapeake Bay. http://www.gypsydancer.co.uk/logs/2006-December.htm.

 

Fish Kills            Fills kills occur when a high amount of nutrients such as nitrates and phosphates combined with the increase of sunlight associated with the summer months increase the productivity of planktonic organism and anaerobic bacteria.

Blounts Bay Fish Kill 2006

Fish Kill-Pamlico River: http://h2o.enr.state.nc.us/esb/prrt.html.

Hurricanes    Tropical Storms and Hurricanes (as known in the North Atlantic) are members of a family of seasonal low pressure storm systems known as tropical cyclones.  Cyclones form in tropical and temperate regions of the world’s oceans and increase in intensity based upon weak upper level winds, warm season, and high moisture content in the atmosphere.  Tropical Storms have winds ranging from 34 knots to 63 knots and hurricanes have winds of at least 63 knots and can potentially reach as high as 165 knots.  Hurricanes also produce large waves which erode away at the coastline.  The strength of the winds and the low pressure can create a storm surge which can flood regions far inland from coastlines.

File:Hurricane Isabel 18 sept 2003 1555Z.jpg

 Hurricane Isabel at Landfall (2003): http://www.mdsg.umd.edu/issues/communities/hazards/.

Hypoxia            Hypoxia is a condition in which there is little dissolved oxygen in a body of water.

Inlet            Inlets are exposed openings in beaches, islands, sandbars, or spits where water from an inland estuary and the ocean meet.  At inlets, strong currents exist and are often hard to navigate due to the presence of sandbars and changing tides which impact the presence of navigable channels.  Inlets control the net water flow in and out of estuaries. 

Oregon Inlet, NC: http://science.nationalgeographic.com/science/photos/weathering-erosion-gallery/outer-banks-sandbars.html.

Longshore Current            Longshore currents travel parallel to a coastline due to the breaking of waves on the shore.

Longshore Drift/Transport            Longshore Transport is the redistribution of sediments such as sand parallel to the shoreline.  This is cause by the longshore current and may result in erosion in one spot and redistribution in another.  Longshore transport is important in the formation of spits and sandbars and the movement of an inlet.

Nor’easter             A Nor’easter is a non-tropical coastal storm generally forming between October and May.  Unlike a hurricane, nor’easters are cold core and are much larger in size.  They will form from a cold front and then gather energy over waters off of the east coast.  The result is a storm similar in nature to a hurricane.  However, winds in nor’easters are not centered around an eye; they are distributed throughout the low-pressure system.  Nor’easters generally have similar effects as hurricanes, but snow is often associated with them and they do not have winds as strong as hurricanes.  The Nor’easter of 1993 brought 11.3 feet of storm surge and eleven tornadoes to Florida as well as 50 inches of snow to Mt. Mitchell, NC.  There was snow reported as far south as southern Louisiana.  Nor’easters are generally especially sever in the winter months when frigid arctic air meets with mild and humid air from the Gulf of Mexico.

Satellite image by NASA of the superstorm on March 13, 1993, at 10:01 UTC.

 “Storm of the Century” Nor’easter of 1993: http://anytimeweather.com/images/401px-Storm_of_the_century_satellite.gif.

Salinity       Salinity is the total mass of all dissolved salts in one kilogram of seawater.  Expressed in parts per thousand (ppt).  Salinity in the ocean is typically 35 ppt and varies slightly around the world depending on the input from sources and output into sinks.   

Salt Marsh             A salt marsh is an ecosystem centered about an intertidal zone that exposes a mud flat during low tide and is inundated by water during a high tide.  A large variety of species is found here including chordgrasses that dominate the landscape.

Salt Marsh in Eastern North Carolina: http://dcm2.enr.state.nc.us/ims/wetlands/wtypdesc.htm.

 

Sandbar            Sandbars are masses of sand that accumulate due to currents that redistribute the particles.  Sand bars occur in inlets and parallel to beaches.  Sandbars also cause waves to break prior to the shoreline and offer a line of defense for beaches. 

Example of a Sandbar: http://www.hawar-islands.com/blog/media/blogs/kuwait/Zour-Sandbar.jpg.

Sand Budget         A sand budget is a way to observe and record changes in amount of sand on a beach or in the nearshore zone by comparing the rate of sand input to the rate of sand output and storage.

Storm Surge           Storm surge is the water level rise associated with a landfalling low pressure system.  Storm surge can range from slightly above the mean high tide water level to upwards of 30 feet above the mean high tide level in especially severe storms.  Storm surge impact can extend miles inland from the coastline and can be devastating to life and property.

File:Hurricane Isabel flood water.jpg

Storm Surge from Hurricane Isabel in Hampton, VA: http://www.penbaymedia.com/images/library/general_photos/flooding2.jpg

Tropical Storms            Tropical Storms and Hurricanes (as known in the North Atlantic) are members of a family of seasonal low pressure storm systems known as tropical cyclones.  Cyclones form in tropical and temperate regions of the world’s oceans and increase in intensity based upon weak upper level winds, warm season, and high moisture content in the atmosphere.  Tropical Storms have winds ranging from 34 knots to 63 knots and hurricanes have winds of at least 63 knots and can potentially reach as high as 165 knots.  Hurricanes also produce large waves which erode away at the coastline.  The strength of the winds and the low pressure can create a storm surge which can flood regions far inland from coastlines.

Sand Dune            A sand dune is a mass accumulation of sand that forms ridges along a coast and serves as a line of defense for a shoreline.  Dunes protect inland habitats from rising water levels and the force of waves.

Dune on the Outer Banks: http://farm4.static.flickr.com/3010/2673277700_e3881a3a72.jpg?v=0.

Text References:

Pinet, Paul R. Invitation to Oceanography.  Sudbury, MA: Jones and Bartlett Publishers, 2006.