The amphidromic point, amphidromic systems

Good starting point - The dynamic theory of tides

1932 Bulletin of the National Research Council, Issues 77-80 (theorizes about multiple nodes for each harmonic)

Animation showing amphidromic systems and nodes - page where animation is from

Uni of Alaska

At and near the system's central point the tidal range is nil

The tidal range is zero at the amphidromic point and increases with distance from this point,

Principles of Tidal Sedimentology

Image from book

Elements of Marine Ecology

Essentials of Oceanography

Oceanography: An Invitation to Marine Science

Virginia Institute of Marine Science

page with many sources many no longer working

from an online Oceanography quiz


The center of an open-ocean tidal system is called a(n) __________.
(a) cotidal point
(b) amphidromic point
(c) ebb current
(d) tidal bore

(b) amphidromic point

The center of an open ocean tidal system is called a(n) __________.
(a) amphidromic center.
(b) cotidal center
(c) rotary center
(d) seiche
(e) tidal flux

(a) amphidromic center.

Due to the shape of the North Sea, it develops two amphidromic points.
(a) True
(b) False

(a) True


An amphidromic point is ____________.
(a) a "no tide" point in the ocean around which the tide crest rotates through one tidal cycle
(b) a place in the ocean where tides are highest
(c) a place in the ocean where tidal datum is displaced to the right (in the northern hemisphere),
or to the south (in the southern hemisphere)
(d) a "no tide" point at the coast where there is a daily high tide, but no low tide

(a) a "no tide" point in the ocean around which the tide crest rotates through one tidal cycle

New theory about currents (pdf)