Document Type

Data Set

Publication Date

2021

Keywords

Western Gulf of Maine, Jeffreys Ledge, Continental Shelf, Seafloor, Sediment, Photographs

Department

Center for Coastal and Ocean Mapping

Disciplines

Geology | Geomorphology | Oceanography | Sedimentology

Description or Abstract

Jeffreys Ledge is a major physiographic feature in the western Gulf of Maine (WGOM) located ~50 km off the coast of New Hampshire, although coming within ~10 km of shore by Cape Ann, Massachusetts. Jeffreys Ledge rises up as much as ~150 m from the seafloor of the adjacent basins (i.e., Scantum Basin or Wilkinson Basin) to depths less than 50 m on the ridge surface. The ridge extends over 100 km along its north-northeast to south-southwest axes while generally only being 5 to 10 km in width (~20 km maximum). Jeffreys Ledge and the surrounding region, like many features in the Gulf of Maine, most likely owes its origin and morphologic and sedimentologic features to a combination of fluvial erosion in the late Neogene (formerly Tertiary) which left topographic highs, subsequent glaciations and sea-level fluctuations in the Quaternary, and late Pleistocene and Holocene marine processes.

In 1998, the National Marine Fisheries Service established the WGOM Closure which encompasses the northern and middle reaches of Jeffreys Ledge. The closure, one of the largest in the world, extends ~110 km north-south and is ~30 km in width. A year-round prohibition of bottom gillnets and otter trawls was implemented in an effort to help rebuild the groundfish stocks in the WGOM (e.g., cod, haddock, other gadids, and flatfish), as well as to help protect habitat.

From 2002 to 2004, the University of New Hampshire (UNH) Center for Coastal and Ocean Mapping (CCOM) was part of an interdisciplinary effort to evaluate the effect of the WGOM Closure on bottom habitats. The study focused on an approximately 18.5 by 27.8 km area (~515 km2) on Jeffreys Ledge – referred to as the UNH Study Area – that encompassed similar seafloor types inside and outside of the closure (Figure 2). During this study, high resolution multibeam echosounder (MBES) surveys were completed, bottom sediment samples were collected and processed for grain size, and seafloor video was obtained along bottom transects.

The “New Hampshire Continental Shelf Geophysical Database: 2002-2005 Jeffreys Ledge Field Campaign – Seafloor Photographs and Sediment Data” presented here was developed by the UNH Center for Coastal and Ocean Mapping/Joint Hydrographic Center (CCOM/JHC) and includes 687 seafloor photographs, grain size data and classifications for 123 bottom sediment samples, and bottom sediment classifications based on video for 142 stations from the UNH Study Area.

DOI

https://dx.doi.org/10.34051/d/2021.8

Grant/Award Number and Agency

University of New Hampshire/National Oceanic and Atmospheric Administration Joint Hydrographic Center Award Number NA10NOS4000073, the UNH Northeast Consortium (NEC), and the UNH Atlantic Marine Aquaculture Center (AMAC)

Access

Public (open access)

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