cape hatteras the confluence of the south & mid atlantic bight provinces and the appalachians...

Cape Hatteras the Confluence of the South & Mid Atlantic Bight Provinces and the Appalachians & the Gulf Stream

On Events and Implications

Part I

Len Pietrafesa, Shaowu Bao, Tingzhuang Yan, Paul Gayes,Jim Epps

The “confluence”Is clearly depictedIn this AVHRR SSTWhere 6o C watersMeet 12o to 20o Waters

And Cold, Dry Air Masses encounterWarm, MoistGulf StreamConditioned Air Masses

Cape Hatteras has many special propertiesLike multiple cross shelf fronts

And topographic influences,Which induces SB and SlopeUpwelling ~ 10-1 cm/sec

Thus creating a very complex Air- Sea interaction system

And conditions for “explosive cyclogenesis”=> D(D(T))/DXDZ = maximum baroclinicity => an atmospheric “bomb”

The spawning or further intensification of ETCsleft: The New England Blizzard of 2004

a) Onset of an ETC

b) of ~ 100 cm/sec and waves of height (O) 5-10 meters; effecting huge Shear Stresses => bottom resuspension and lateral erosion

c) Note MAB waters breeching Diamond Shoals down into Raleigh Bay

d) The system relaxesAfter 7- 8 days

• So, ETCs carry heat northward… and• drop heavy precipitation …and• are characterized by southward to southwestward , i.e. northeasterly winds…hence

the term “Nor’Easters” • which move blue crab juveniles from Chesapeake Bay to the south and into the

primary nurseries and settlement areas of Pamlico Sound via Oregon Inlet …and also…• Bottom sediments are picked up by storm induced waves and currents and along with

the Chesapeake Bay Plume also enter the Inlets

• The sediments follow a track similarto the crabs. The dirt ends up going through Oregon Inlet and being deposited on the backsides of the Outer Bank, barrier island chain. • This process allows these ephemeral

strips of sand to migrate west toward the mainland, thus ensuring their future during this period of sea level rise

• Estuarine dependent finfish also move across the shelf at the surface and the interior into the Pamlico Sound estuary

Numbers of ETCs13 in 1998 and 24 in 2001

During a low ETC year there is less coastal water in the system than during a high ETC year

With NE’ ly windsHydraulic Heads get createdAlong the axes of the InletsAnd water pours into the system

0

2

4

6

8

10

12

1986 1988 1990 1992 1994 1996 1998 2000 2002

Cat

ch p

er e

ffor

tCluster 1 Cluster 2Cluster 3 Cluster 4

-2

-1

0

1

2

3

4

5

6

7

8

1988 1990 1992 1994 1996 1998 2000 2002

Year Class

Y-O

-Y A

bu

nd

an

ce In

dex

0

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

7,000,000

Ab

un

dan

ce a

t A

ge (

#s)Y-O-Y

Age 1

Age 2

Variability within age classes. . .

2000 4000 6000 8000 10000

March Discharge

-1.0

-0.5

0.0

0.5

1.0

Clu

ster

4 A

bu

nd

400 600 800 1000

Feb-Mar N-NE Winds

-0.5

0.0

0.5

1.0

Clu

ster

4 A

bu

nd

20 40 60 80 100 120

Feb-Mar E-SE Winds

-0.5

0.0

0.5

1.0

Clu

ster

4 A

bu

nd

Cluster 4 vs. Environmental Factors

Comments:Steve Ross?