The shelf edge system - Introduction to the Physical and Biological Oceanography of Shelf Seas - page 314

(a)

1

0.5

0

-0.5

-1

11 Apr 1 May 21 May 10 Jun 30 Jun 20 Jul

(b)

20

10

0

-10

-20

11 Apr 1 May 21 May 10 Jun 30 Jun 20 Jul

(c)

15

14

12

11

10

11 Apr

1 May 21 May 10 Jun 30 Jun 20 Jul

Date 1995

Figure 10.6 (a) Alongshore component of surface wind stress off northeast New Zealand
during the austral winter, 1995. Negative wind stress is to the southeast and upwelling
favourable; (b) Cross-shelf edge component of currents measured by a current meter 10 metres
above the seabed at the shelf edge (position: 35 30.22' S, 174 54.77' E). The currents
have been low-pass filtered to remove tidal variability; negative flow is on-shelf;
(c) Near-bed temperature measured by the current meter, low pass filtered to remove
tidal variability.

surface flow, with associated eddies and filaments, can export surface material off the
shelf. Also, remember that if the wind direction is reversed then surface water piles up
against the coast, generating a surface slope that will push deep shelf water towards
the shelf edge and the open ocean. We then have a mechanism for exporting deep
shelf water and importing surface oceanic water. We shall explore the biogeochem-
ical and ecological consequences of these transports later in this chapter.