REGIONAL ISSUES
SEA LEVEL RISE
What is Sea level rise?
Studies of global sea level show that there has been a substantial increase in the level of the world’s oceans, and not only are sea levels rising; but the rate at which they are rising has increased as well.
At this time, research shows that “sea level rise” (SLR) is an adverse effect of multiple environmental concerns linked to climate change. Including, but not limited to, thermal expansion, glacial ice melt, increased atmospheric heat from the burning of fossil fuels or other greenhouse gas emissions, etcetera. As emissions and average global temperature continue to climb, so will global sea levels.
In 2014, global sea level was 2.6 inches above the 1993 average- the highest annual average in satellite record. NOAA (2/26/21)
The rate of sea level rise is not consistent globally. Meaning that, depending upon the coastal region, the amount sea levels have risen could be observed as lesser or greater than the determined global average. That is why it is important to understand the effects of sea level rise not only globally, but locally.
Throughout the Mid-Atlantic region, communities have felt the effects of a changing climate and rising sea levels over the past few decades, and have felt the issue more severely than other areas of the country.
Sea Grant state programs within the region are working with communities, researchers, policymakers, and businesses to prepare, educate, and assist coastal communities as further issues associated with sea level rise arise.
Frequency of flooding
along U.S. coasts
2011-2020 vS. 1950-1959
Causes
There are multiple factors contributing to globally rising sea levels. One factor, known as thermal expansion, involves warming of the oceans due to increased greenhouse gas emissions. Another is the result of glacial ice melting and beginning to increase flow throughout the region. Land subsidence due to groundwater withdrawal and other issues is a major concern in the Mid-Atlantic.
When people burn fossil fuels, elements are emitted which trap heat in the atmosphere, this is known as the greenhouse effect. As human population has grown over the past century, there has been a substantial increase in the amount of greenhouse gases entering the atmosphere. The world’s oceans naturally absorb atmospheric heat. The sea is an even greater carbon sink than the Amazon rainforest, and a rise in emissions has proven to be detrimental to ocean acidity and temperature. Studies show that about 90% of total heating from increased emissions in the atmosphere are being absorbed by ocean water. When you heat water, the molecules are going to expand and upwell. This process has led to what is known as “thermal expansion.”
Global sea level has also risen due to the melting of glaciers and ice shelves, again due to increase in atmospheric heat. From March to September, the Arctic is bathed in permanent sunlight, and as the dark and brackish waters are exposed to the sun, they begin to absorb that atmospheric heat, leading to further melt. Studies show that due to constant absorption within those 7 months has led to Arctic waters warming at twice the rate of the rest of the world. Maximum ice extent in the Arctic has decreased considerably from the 1982-2010 average, or even from 2012, compared to the past few years. Though this change may not look so severe in the graph, the extent of ice has gone from well over 15 million square km, to just above 14 million sq. km in the past 9-37 years.
The ice shelves in Antarctica are so large they have their own gravitational pull, and as the ice in Antarctica pulls in warmer waters from around the globe, further melt occurs. Today’s ice sheets and glaciers hold enough water to cause 68-70 m of sea level rise.
Ice melt in Antarctica is especially detrimental to the Mid-Atlantic region, and may be a part of the reason that sea levels have risen higher here than the global average. It seems that waters from ice melt are flowing into the Northern Hemisphere and pooling off of the Northeastern coasts of the United States. This is a large part of the reason sea levels in the Mid-Atlantic region are higher than the global average. For example, since the end of the 19th century, sea levels in New York have risen about a foot, and in North Carolina and Virginia they have risen about a foot and a half, compared to the global average of 9 inches.
Another issue which has caused increase concern over sea level rise is land subsidence due to groundwater withdrawal. Groundwater makes up only 0.77% of the water on Earth, but it supplies a large portion of the U.S. with freshwater. There are many concerns linked to groundwater and sea level rise. As stated previously, groundwater withdrawal can lead to land subsidence which can increase threat of SLR in certain areas, specifically in the Chesapeake Bay region. Researchers have found that deep drilling for groundwater may be contributing to sea level rise even more than melting glaciers.
Already in the region of the Chesapeake Bay there are many low-lying wetlands and sensitive ecosystems threatened by sea level rise and possible changes in salinity. Other threats such as coastal land erosion, induation, and storm surges are a threat to these freshwater reserves. If land subsidence continues to occur, these habitats and water sources could be at serious risk.
Threats To Region
Effects of sea level rise can be felt throughout the Mid-Atlantic region in the form of more frequent and severe storms, and the prospect of saltwater infiltration. Coastal lands are being lost to erosion, and frequent flooding as a result of sea level rise has had a negative impact on coastal communities, species and their ecosystems.
As thermal expansion causes oceans to rise in temperature, oceanographers predict that warmer ocean temperatures will support more severe storm surges. The frequency of these storms, as the ocean begins warming, is also a major cause of concern for both coastal and inland communities. Evidence to support this has been seen throughout the region in recent hurricane seasons. Storm and flooding events which were at one point considered 1 in 100 years, are happening much more frequently.
As sea levels continue to rise, a threat to communities throughout the region is saltwater infiltration into tidal streams and groundwater. Naturally, these freshwater and saltwater zones are separated by seaward movement, and there is a transition area where the saltwater and freshwater mix; but as sea levels rise, freshwater stores may be diminished as saltwater begins to encroach upon them. This issue of salt line migration would impact tidal rivers and streams just as much, if not more quickly, than groundwater. The threats do not only effect beach communities, these issues could be a big problem for states like Pennsylvania as well.
Another cause for concern, as sea level has increased, is a phenomenon known “sunny day flooding.” This can be simply defined as flooding resulting from daily high tide. Over the years, daily average high tides have begun to climb from 1.75 to 2 feet above average sea level. As this water bubbles up from storm drains and onto streets or walkways on visibly clear days, the issue has been deemed “sunny day flooding.” This is especially concerning to communities which have witnessed this issue. If daily high tide is already causing flooding, then storms- even slight storms- could mean a catastrophic flooding event.
Sea level rise poses a threat not only to our communities, but to our nation’s wildlife and coastal ecosystems as well. The Center for Biological Diversity reported that 233 threatened or endangered species in coastal states are at risk from sea level rise. More frequent and severe storm surges threaten to erode or submerge critical habitat for many species.
Measuring Sea Level Rise
There are multiple technologies which have allowed scientists to determine the level of the world’s oceans. Primarily, measurements of global sea levels are found through the uses of satellite laser altimeters; however, tide stations are a valuable resource for localities to measure sea levels.
Tide stations are more effective in measuring the day to day height of surrounding waters in a specific location. Tide stations are valuable not only in providing communities with information that aids in safe navigation and other coastal activities; but also in measuring sea level rise over time which is specific to the region. Tide gauges can give states a more individualized look at how sea level rise is, and could be, effecting their area.
For more info on tide stations in your state, click here…
economic Impacts
Many coastal communities in the Mid-Atlantic region rely on coastal activities and tourism to supplement their economies. According to New Jersey Sea Grant, the entire state’s economy relies heavily on coastal and marine resources. Coastal economy in Delaware contributes $7 billion to the state on average. Obviously coastal states feel the immediate effects of sea level rise both physically and economically; but there is serious economic threat to “land-locked” states as well.
Pennsylvania is the only state within the Mid-Atlantic region without direct access to coastal shoreline. However, Pennsylvania’s connection to the Delaware River Basin is one cause of concern to PA Sea Grant and Pennsylvania economy in terms of Sea Level Rise. The Delaware River supplies drinking water to Philadelphia, the largest metropolitan economy in Pennsylvania, and supports the largest freshwater port in the world. The basin contributes billions annually in water supply, hunting/ fishing, recreation, amongst many other economically beneficial activities.
As sea levels continue to rise, the river’s shoreline has risen as well, estimated about 1 inch every 8 years. The freshwater wetlands along the river may see a change in inhabitants- from native freshwater plants, to more salt-tolerant species. This could not only impact plants, but also fish and other organisms which rely on the freshwater of the stream; thus impacting Pennsylvania economy through loss of recreational activities like fishing or hunting in the area. Higher salinity could also negatively impact economy throughout Pennsylvania, but especially in Philly where saltwater could move up into the city’s drinking water supply.
INFORMATION ABOUT SEA LEVEL RISE IN:
- DELAWARE
- MARYLAND
- NEW JERSEY
- NEW YORK
- NORTH CAROLINA
- PENNSYLVANIA
- VIRGINIA
- UNITED STATES