The Sea South is named because it was south of the Jaredite Land Northward:
And it came to pass that they did multiply and spread, and did go forth from the land southward to the LAND NORTHWARD, and did spread insomuch that they began to cover the face of the whole earth, from the SEA SOUTH to the sea north, from the sea west to the sea east. (Helaman 3:8)
Most modelers (99.9%) ignore the Sea South reference, as do they the Sea North. Of the few who do recognize it, most incorrectly place it south of the Land Southward; we are never told what was south of where Lehi landed; all migrations were northward. Some believe those sea references are just a metaphor:
The reference to north and south seas fits nicely into the Mesoamerican scene as part of a metaphor for the whole earth and was probably used in a metaphorical sense in the Book of Mormon” (A Key For Evaluating Nephite Geographies by John E. Clark in FARMS Review: Vol. 1, Issue 1, pp. 20-70 A review of “Deciphering the Geography of the Book of Mormon” by F. Richard Hauck Provo, Utah: Maxwell Institute, 1989, p. 65).
I am convinced that the reference to a north sea and a south sea is devoid of any concrete geographical content. All specific references or allusions to Book of Mormon seas are only to the east and west seas. Any geography that tries to accommodate a north and south sea, I think, is doomed to fail (Ibid).
Wilson also raises the question of how the sea north and sea south fit with the Limited Geography Model (3b), a matter which has been fully analyzed by John Clark.(Clark, “Key for Evaluating,” 63–67) The north and south seas are mentioned only twice (Helaman 3:8; Alma 22:32), in a vague general sense. Clark rightly attributes these references to common ancient macrogeographical world-views of the earth surrounded by the primordial “ocean.” THUS THE MINOR AND VAGUE MENTIONS OF THE NORTH AND SOUTH SEAS REFER TO MACROGEOGRAPHICAL COSMIC WORLD-VIEWS OF SEAS SURROUNDING THE ENTIRE LANDMASS, RATHER THAN SPECIFIC IDENTIFIABLE BODIES OF WATER (“Basic Methodological Problems with the Anti-Mormon Approach to the Geography and Archaeology of the Book of Mormon, William J. Hamblin, Journal of Book of Mormon Studies: Volume – 2, Issue – 1, pp. 161-97, Provo, Utah: Maxwell Institute, 1993).
Despite such attempts to disregard the text, what can’t be ignored are the “seashore” references to the Sea South:
11 And it came to pass that in the first year of Lib, Coriantumr came up unto the land of Moron, and gave battle unto Lib.
12 And it came to pass that he fought with Lib, in which Lib did smite upon his arm that he was wounded; nevertheless, the army of Coriantumr did press forward upon Lib, that he fled to the borders upon the seashore.
13 And it came to pass that Coriantumr pursued him; and Lib gave battle unto him upon the seashore.
14 And it came to pass that Lib did smite the army of Coriantumr, that they fled again to the wilderness of Akish.
15 And it came to pass that Lib did pursue him until he came to the plains of Agosh. And Coriantumr had taken all the people with him as he fled before Lib in that quarter of the land whither he fled.
16 And when he had come to the plains of Agosh he gave battle unto Lib, and he smote upon him until he died; nevertheless, the brother of Lib did come against Coriantumr in the stead thereof, and the battle became exceedingly sore, in the which Coriantumr fled again before the army of the brother of Lib. (Ether 14)
The background for that account is the Land of Moron was along the west side, by the Narrow Neck. The only way to escape was east along the seashore of the Sea South. Any model lacking a Sea South, south of the Jaredite Land Northward is incorrect, just as any model lacking a Sea North, north of the Jaredite Land Northward.
Before the land was lifted up at the Coming of Jesus, the water flowed freely from Lake Erie into ancient Lake Tonawanda [Sea that Divides the Land & Sea South] via Tonawanda Creek. Even today, part of Tonawanda Creek is being used to flow water inland from Lake Erie into the Erie Canal; otherwise, it flows into Lake Erie.
The amount the land was lifted up is the amount they had to dig down for the Erie Canal beginning in Lockport (see Lockport lock system for the Erie Canal http://www.lowbridgeproductions.com/erie-canal-images-southern-route.html).
Tonawanda Creek is the lowest part of ancient Lake Tonawanda today and it can be traced east to the city of Batavia (the “Batavia Moraine” theory is flawed because it was inaccessible being on the opposite side of Tonawanda Creek and it did not extend all the way through Lake Tonawanda–current-day swamp lands) where it makes a sharp turn south and continues to follow the southward flow via the “LITTLE Tonawanda Creek” through the city Dale where it entered the Wyoming Valley eventually merging with the Genesee River in the Genesee Gorge.
This southward water flow during the upheaval at the time of the coming of Christ was noted by Frank Leverett:
It is a matter of much significance that these pitted gravel plains appear at levels far below the level of Lake Warren and in positions where it would seem probable that the lake had free access to the ice margin. Those near Oakfield are fully 100 feet below the level of the neighboring part of the beach of Lake Warren, while those along the border of Aliens Creek are 150 to 250 feet or more below the beach. There is a gravel plain just west of Scottsville on the north side of Allens Creek which stands between the 580 and 600 foot contours, or about 275 feet below the beach of Lake Warren. This has been extensively opened for gravel in a direction favorable for showing the mode of formation, there being a pit about one-fourth of a mile long extending from north to south across the gravel plain. The bedding shows that it was built by a stream moving SOUTHWARD away from the ice sheet but up the Genesee Valley. The beds were built out from NORTH TO SOUTH in the form of a DELTA, the topset and foreset beds being well exposed. The dip of the foreset beds is most abrupt in the middle part of the pit, being 25Â° to 30Â° below the horizontal. With the advance of the delta southward the angle of dip decreases to 10Â° or less. The material is a sandy gravel with many stones 2 or 3 inches in diameter. It is, on the whole, finer and less distinctly assorted than in the outwash gravels formed in situations where the water had free escape. If Lake Warren still persisted the material contained in this delta and other gravelly deposits along the southern border of the drumlin belt seems likely to have been forced out by hydrostatic pressure from the edge of the ice sheet into the bordering lake (Frank Leverett, Glacial Formations and Drainage Features of the Erie and Ohio Basins, 1920, p. 694).