Less-than-global sea-level changes

["David Marjanovic" <david.marjanovic@gmx.at>]

Against my expectations I've found the original paper!

Jon E. Mound & Jerry X. Mitrovica: True Polar Wander as a Mechanism for
Second-Order Sea-Level Variations, Science 279, 534 -- 537 (23 January 1998)

Abstract:
"Long-term wander of the rotation pole can be a significant contributor to
second-order (time scales of ~100 million years) sea-level variations.
Numerical predictions based on realistic viscoelastic Earth models and
paleomagnetically constrained polar motion yield global-scale, differential
sea-level trends that can be as large as ~200 meters. From the results
presented here, it is argued that the well-documented, second-order,
Cretaceous-Tertiary sea-level cycle should be reinterpreted as some
combination of a eustatic and a regionally varying rotational signal."

Note that Fig. 2 depicts true, not apparent, polar wander = it is already
corrected for plate tectonics. If it weren't, the pole would be shown as
being very close to Alaska in the Late Cretaceous when Alaska was about at
85 °N (for some time at least).

More quotes (refs and mentions of figures removed):

"In this case, the sea-level perturbation is zero on two great circles: the
first at 90° from the instantaneous pole of rotation, and the second
oriented perpendicular both to the first great circle and to the
instantaneous great circle path of the pole. These two great circles define
four quadrants. When the local rotation pole (that is, the north pole in the
Northern Hemisphere and the south pole in the Southern Hemisphere) is moving
toward a quadrant, sea level falls in that quadrant. Conversely, when the
local rotation pole is moving away from a quadrant, sea level rises in that
quadrant. The great circles of zero sea-level change associated with the
mean motion of the rotation pole over the past 10 My lie roughly on the
equator and the great circle defined by 51°E and 231°E."

"the maximum sea-level change is obtained at 45° from the poles"

"A comparison of Figs. 1, 2, and 3 suggests that TPW may have influenced the
second-order, sea-level cycle over the last 130 My. The change in the
direction of TPW at ~50 Ma roughly coincides with the reversal in the
long-term sea-level trend. Quadrants containing sites in North America,
Europe, North Africa, and Australia should have experienced some amount of
TPW-induced sea-level rise from 130 to 50 Ma (as the local pole moved away
from these quadrants) followed by a sea-level fall since 50 Ma (as the pole
changed direction in the hot-spot frame), consistent with the geological
record of sea-level change over the same period. The trend would be reversed
for sites in the remaining two quadrants."

"Our results suggest that TPW-induced sea-level changes can contribute
significantly to second-order sea-level cycles. Furthermore, TPW effects
cannot be ignored when one is comparing or combining sea-level data from
different geographic regions. The often-cited correlation between spreading
rates and sea-level fluctuations (5) is consistent with a sizeable
TPW-induced sea-level signal. Recent modeling studies (33) have shown that
the observed TPW path is consistent with predictions obtained by
back-advecting seismically inferred density heterogeneities. Thus, TPW
speeds (and the associated sea-level fluctuations) are likely linked to
spreading rates, which reflect the rate of advection. The second-order
sea-level cycle since 130 Ma is likely a combination of a TPW-induced
(quadrant-localized) signal and a eustatic trend, for example, one that
depends on changes in ocean basin volume that may arise from variations in
spreading rates. A careful analysis of sea-level data, which include a
globally distributed network of sites, will be required to distinguish the
relative importance of each contributor."

"Sea-level variations, as reflected in stratigraphic cycles, are classified
in terms of their duration. For example, following [...], we define
second-order cycles as lasting 10 million to 100 million years and
third-order cycles as lasting 1 million to 10 million years."