Methodology 30 sites, were chosen, including barrier islands, beaches exposed to open ocean, and...

1
0% 20% 40% 60% 80% 100% June July A ugust Month Long B each,G loucester,Sum m er2009 Sily/C lay V ery Fine S and Fine S and M edium S and C ourse S and Granules Pebbles 0% 20% 40% 60% 80% 100% June July A ugust M onth Long B each,G loucester,Sum m er2010 Sily/Clay V ery Fine S and Fine S and M edium S and C ourse S and Granules Pebbles 0% 20% 40% 60% 80% 100% June July A ugust M onth C edarP oint, S cituate:2009 % Silt & C lay % VeryFine Sand % Fine Sand % M edium Sand % C ourse Sand % G ranules % Pebbles 0% 20% 40% 60% 80% 100% June July M onth C edarP oint, S cituate:2010 S ilt/C lay V ery Fine S and Fine S and M edium S and C ourse S and G ranules P ebbles 1 11 18 0 5 10 15 20 Num berof Beaches finer little change coarser Change in G rain S ize C hange in G rain Size from Sum m er2009 to 2010 Methodology •30 sites, were chosen, including barrier islands, beaches exposed to open ocean, and beaches partially shielded by offshore geological features •Each site was visited in June, July, and August of 2009 and 2010 •Core samples were collected during each visit, and beach widths and height of sea walls or positions of dunes were measured •Samples were brought back to the university lab, soaked in sodium hexametaphosphate, dried in a geo-oven, and sorted by grain size in a graduated sieve •Data were compiled to look for coarsening of sediments, and changes in beach Caitlin Herbert ([email protected] ); Andrea Hofius ([email protected] ); Cristin Ashmankas ([email protected] ) Natural Sciences Department, Lesley University Abstract This project is a continuation of research that began in the summer of 2009, when the principal investigator began gathering data in an attempt determine the effects of climate change on the Massachusetts coastline. One factor contributing to increased erosion is frequent and severe storm activity, which is predicted to become more common as global temperatures rise. The erosional effects of these storms can be detected by collecting sand samples from beaches and sorting them to determine grain size distribution. Storms are associated with coarsening of beaches, as rapidly moving water tends to transport finer sediments from the shoreline area and deposit them offshore, leaving larger grains behind. A second indicator of erosion is a narrowing of beaches, as rising sea levels gradually submerge portions of gently sloping shorelines. In 2009, 30 different sites were chosen North of Cape Cod, including barrier islands, mainland coasts exposed to open ocean, and beaches partially shielded by offshore islands, spits, or baymouth bars. Sites varied by degrees of coastal development, from beaches with mostly intact dune and lagoon systems, to those punctuated by seawalls, jetties, and roads and buildings. All locations were recorded using a GPS unit, which was then used to locate the sites on subsequent visits. Once per month from June through August 2009 and 2010, three sediment samples were taken from the foreshore of each site using a corer, and the distance from the high tide line to a sea wall or dunes was measured. Samples were then brought back to the university lab, where they were soaked in sodium hexametaphosphate, which is used as a dispersing agent to separate small particles. They were then dried and sorted by grain size in a graduated sieve. The data were then compiled to look for correlations between changing distribution of grain sizes over time, changes in beach width over time, and frequency of storms. Erosion in Fourth Cliff, Marshfield July 2010 NASA-GISS Surface Temperature Anomaly Source: http://data.giss.nasa.gov/gistemp/2010ju ly/ Beach Sites Long Beach, Gloucester Cedar Point, Scituate Conclusion Our analysis of the data from this year indicated that in more than half of the beach sites, the overall grain size had become much coarser since the previous summer, most likely due to erosion from sea level rise. In addition to this, many beaches also became narrower, while others have consistently had high tide lines at their sea walls or dunes, leading to a consistent width of zero meters. More long-term trends will require the collection of additional data over the coming years.

Transcript of Methodology 30 sites, were chosen, including barrier islands, beaches exposed to open ocean, and...

Page 1: Methodology 30 sites, were chosen, including barrier islands, beaches exposed to open ocean, and beaches partially shielded by offshore geological features.

0%

20%

40%

60%

80%

100%

June July August

Month

Long Beach, Gloucester, Summer 2009Sily/Clay

Very FineSandFine Sand

Medium Sand

Course Sand

Granules

Pebbles0%

20%

40%

60%

80%

100%

June July August

Month

Long Beach, Gloucester, Summer 2010

Sily/Clay

Very Fine Sand

Fine Sand

Medium Sand

Course Sand

Granules

Pebbles

0%

20%

40%

60%

80%

100%

June July August

Month

Cedar Point, Scituate: 2009

% Silt & Clay

% Very Fine Sand

% Fine Sand

% Medium Sand

% Course Sand

% Granules

% Pebbles

0%

20%

40%

60%

80%

100%

June July

Month

Cedar Point, Scituate: 2010 Silt/Clay

Very FineSandFine Sand

Medium Sand

Course Sand

Granules

Pebbles

1

11

18

0

5

10

15

20

Nu

mb

er o

f B

each

es

finer little change coarser

Change in Grain Size

Change in Grain Size from Summer 2009 to 2010

Methodology

•30 sites, were chosen, including barrier islands, beaches exposed to open ocean, and beaches partially shielded by offshore geological features

•Each site was visited in June, July, and August of 2009 and 2010

•Core samples were collected during each visit, and beach widths and height of sea walls or positions of dunes were measured

•Samples were brought back to the university lab, soaked in sodium hexametaphosphate, dried in a geo-oven, and sorted by grain size in a graduated sieve

•Data were compiled to look for coarsening of sediments, and changes in beach widths

Caitlin Herbert ([email protected]); Andrea Hofius ([email protected]); Cristin Ashmankas ([email protected]) Natural Sciences Department, Lesley University

AbstractThis project is a continuation of research that began in the summer of 2009, when the principal investigator began gathering data in an attempt determine the effects of climate change on the Massachusetts coastline. One factor contributing to increased erosion is frequent and severe storm activity, which is predicted to become more common as global temperatures rise. The erosional effects of these storms can be detected by collecting sand samples from beaches and sorting them to determine grain size distribution. Storms are associated with coarsening of beaches, as rapidly moving water tends to transport finer sediments from the shoreline area and deposit them offshore, leaving larger grains behind. A second indicator of erosion is a narrowing of beaches, as rising sea levels gradually submerge portions of gently sloping shorelines.

In 2009, 30 different sites were chosen North of Cape Cod, including barrier islands, mainland coasts exposed to open ocean, and beaches partially shielded by offshore islands, spits, or baymouth bars. Sites varied by degrees of coastal development, from beaches with mostly intact dune and lagoon systems, to those punctuated by seawalls, jetties, and roads and buildings. All locations were recorded using a GPS unit, which was then used to locate the sites on subsequent visits. Once per month from June through August 2009 and 2010, three sediment samples were taken from the foreshore of each site using a corer, and the distance from the high tide line to a sea wall or dunes was measured. Samples were then brought back to the university lab, where they were soaked in sodium hexametaphosphate, which is used as a dispersing agent to separate small particles. They were then dried and sorted by grain size in a graduated sieve. The data were then compiled to look for correlations between changing distribution of grain sizes over time, changes in beach width over time, and frequency of storms.

Erosion in Fourth Cliff, Marshfield

July 2010 NASA-GISS Surface Temperature Anomaly Source: http://data.giss.nasa.gov/gistemp/2010july/

Beach Sites

Long Beach, Gloucester

Cedar Point, Scituate

Conclusion

Our analysis of the data from this year indicated that in more than half of the beach sites, the overall grain size had become much coarser since the previous summer, most likely due to erosion from sea level rise.

In addition to this, many beaches also became narrower, while others have consistently had high tide lines at their sea walls or dunes, leading to a consistent width of zero meters. More long-term trends will require the collection of additional data over the coming years.