1.1 Introduction
The Straits of Magellan are a natural confluence of water masses from the Pacific and
Atlantic Oceans and are closely linked to the
Antarctic ecosystem (Fig. 1.1). The distance
from the Pacific (Capo Deseado) to Atlantic
(Punta Dungeness) entrances is about 570 km
with a distance from northern to southern
shores that ranges from 4-30km. Along the
main axis, different sills and shelfs separate
specific basins (Fig. 1.2) that playa crucial
role in driving water mass circulation and
shaping current patterns. According to
Antezana et al. (1992), the Straits are divided
as follows:
A. EASTERN SOUTH PACIFIC: located 90 km off
the entrance to the Straits (Evangelistas
Island) with a depth range from 4000 m rising
to 2000m.
B. MAGELLAN SLOPE: located 50-90km off
Evangelistas Island with a depth range from
2000 m rising to 200 m. The slope is very
narrow (20 km wide), bordered by a welldefined sill, 20-50m deep, separating Pacific
waters from those in the Straits. The sill is
located 36km SE of Evangelistas Island,
immediately beyond Pilar Cape.
C. DEEP WESTERN ENTRANCE: located between
Pilar Cape to NE of San Carlos III Islands at
Paso Tortuoso, with a depth range from 501200 m. This basin is limited by two shallow
sills and can in turn be divided, from west to
east, into three sub-basins:
1. Pacific Mouth, from Pilar Cape to Tamar
Island (50-500m depth, 63km long,
18km wide);
Chapter 1 Study Area
2. Paso del Mar, extending from Tamar
Island to Havannah Point (500-1200m
depth, 40km long, 10km wide);
3. Paso Largo, extending from Havannah
Point to San Carlos III Island (50-700m
depth, 75km long, 45km wic;le).
D. INTERMEDIATE PASSAGE: extending from
San Carlos Island to Pelicano Point (N of
Punta Arenas), 50-500m deep (mean depth
of 300 m) and 200 km long. This basin is
widely connected to the west via Bahia Inutil
and Canal Whitehead-Seno Almirantazgo.
Three sub-basins can be identified:
1. Paso Froward, extending from San Carlos
Island to Cape Froward (50-400m deep
on a SE downward slope, 72 km long,
9.9km wide);
2. Seno Magdalena, a transition area on the
southern junction of eastern and western
passages;
3. Paso Ancho, extending from San Isidro
Cape to Pelicano Point (100-350m deep,
90km long on the northward slope, 27km
wide).
E. SHALLOW EASTERN ENTRANCE: extending
from Pelicano Point to Dungenes Point at the
Atlantic entrance to the Straits, 30-50m
deep, 200km long. Three sub-basins are
bordered by the Segunda Angostura and the
Primera Angostura; this is the easternmost
(Atlantic Mouth) as well as the longest and
widest of the channel basins.
F. WESTERN SOUTH ATLANTIC SHELF: extending gradually beyond the entrance at
Dungenes Point into the Atlantic shelf with a
depth range from 50-60 m. There is no clear
The Straits of Magellan are a natural confluence of water masses from the Pacific and
Atlantic Oceans and are closely linked to the
Antarctic ecosystem (Fig. 1.1). The distance
from the Pacific (Capo Deseado) to Atlantic
(Punta Dungeness) entrances is about 570 km
with a distance from northern to southern
shores that ranges from 4-30km. Along the
main axis, different sills and shelfs separate
specific basins (Fig. 1.2) that playa crucial
role in driving water mass circulation and
shaping current patterns. According to
Antezana et al. (1992), the Straits are divided
as follows:
A. EASTERN SOUTH PACIFIC: located 90 km off
the entrance to the Straits (Evangelistas
Island) with a depth range from 4000 m rising
to 2000m.
B. MAGELLAN SLOPE: located 50-90km off
Evangelistas Island with a depth range from
2000 m rising to 200 m. The slope is very
narrow (20 km wide), bordered by a welldefined sill, 20-50m deep, separating Pacific
waters from those in the Straits. The sill is
located 36km SE of Evangelistas Island,
immediately beyond Pilar Cape.
C. DEEP WESTERN ENTRANCE: located between
Pilar Cape to NE of San Carlos III Islands at
Paso Tortuoso, with a depth range from 501200 m. This basin is limited by two shallow
sills and can in turn be divided, from west to
east, into three sub-basins:
1. Pacific Mouth, from Pilar Cape to Tamar
Island (50-500m depth, 63km long,
18km wide);
Chapter 1 Study Area
2. Paso del Mar, extending from Tamar
Island to Havannah Point (500-1200m
depth, 40km long, 10km wide);
3. Paso Largo, extending from Havannah
Point to San Carlos III Island (50-700m
depth, 75km long, 45km wic;le).
D. INTERMEDIATE PASSAGE: extending from
San Carlos Island to Pelicano Point (N of
Punta Arenas), 50-500m deep (mean depth
of 300 m) and 200 km long. This basin is
widely connected to the west via Bahia Inutil
and Canal Whitehead-Seno Almirantazgo.
Three sub-basins can be identified:
1. Paso Froward, extending from San Carlos
Island to Cape Froward (50-400m deep
on a SE downward slope, 72 km long,
9.9km wide);
2. Seno Magdalena, a transition area on the
southern junction of eastern and western
passages;
3. Paso Ancho, extending from San Isidro
Cape to Pelicano Point (100-350m deep,
90km long on the northward slope, 27km
wide).
E. SHALLOW EASTERN ENTRANCE: extending
from Pelicano Point to Dungenes Point at the
Atlantic entrance to the Straits, 30-50m
deep, 200km long. Three sub-basins are
bordered by the Segunda Angostura and the
Primera Angostura; this is the easternmost
(Atlantic Mouth) as well as the longest and
widest of the channel basins.
F. WESTERN SOUTH ATLANTIC SHELF: extending gradually beyond the entrance at
Dungenes Point into the Atlantic shelf with a
depth range from 50-60 m. There is no clear