Different explanations for Morell's error have been suggested. One of them is that Morrell wanted to deceive with this claimed finding. Morrell describes his sighting briefly, and seeks no personal credit or glory from the discovery. In his narrative, he gives all credit to his fellow sealing captain, Robert Johnson, for finding and naming the land two years earlier. Morrell may have been honestly mistaken, through miscalculation of his ship's position or by misremembering detail when writing the account after nine years. Alternatively, he may have made the common error of confusing distant icebergs with land, or been misled by the distorting effects of Antarctic mirage. In 1843 the distinguished British naval explorer James Clark Ross reported possible land in a position close to Morrell's; this land, too, would eventually be proven not to exist.
In the early 19th century the geography of Antarctica was almost completely unknown, but occasional sightings of land had been recorded. Benjamin Morrell sailed to the South Sandwich Islands. Morrel was appointed commander of the schooner "Wasp" for a two-year voyage of sealing, trading and exploration in the Antarctic seas and the southern Pacific Ocean in 1822. In addition to his sealing duties Morrell had, as he put it, "discretionary powers to prosecute new discoveries." He proposed to use this discretion to investigate the Antarctic seas "and to ascertain the practicality ... of penetrating to the South Pole." This would be the first of four long voyages that would keep Morrell at sea for most of the following eight years, although he would not revisit the Antarctic after the initial voyage.
"Wasp" sailed south from New York on 1822. She reached the Falkland Islands late in October, after which Morrell spent 16 days in fruitless searches for the nonexistent Aurora Islands, before heading for South Georgia, where the ship anchored on . In his account Morrell wrongly records the position of this anchorage, placing it in open sea about south-west of the island's coastline. "Wasp" then headed eastwards to hunt for seals. According to Morrell, the ship reached the remote Bouvet Island on . He found this elusive island without apparent difficulty. Historian H.R. Mill notes that Morrell's description of the island's physical features fails to mention the island's most singular characteristic—it is covered by a permanent ice sheet. Morrell then attempted to take the ship southwards. He reached think ice around 60°S and decided to turn northeast towards the Kerguelen Islands where he anchored on .
After several days of exploration and evidently profitable sealing, "Wasp" left the Kerguelens on 1823, sailing south and east to record her furthest eastern position at 64°52'S, 118°27'E on . From this point, according to his own account, Morrell decided to take advantage of strong easterly winds, and made a rapid passage westward back to the Greenwich meridian, 0°. His account is light on details, but indicates that a distance of more than was covered in 23 days. The credibility of this claim of such fast, direct travel in ice-infested waters has been widely disputed, particularly as Morrell quotes southerly latitudes during the voyage which later proved to be at least 100 miles inside the then undiscovered Antarctic continental mainland. On "Wasp" reached Candlemas Island in the South Sandwich Islands. After a few days spent in a search for fuel to feed the ship's stoves "Wasp" sailed southwards on , into the area later known as the Weddell Sea. Finding the sea remarkably free of ice, Morrell advanced to 70°14'S before turning north-westward on . This retreat, Morrell says, was due to the ship's lack of fuel; otherwise, he claims, in these open waters he could have taken the ship to 85°, or perhaps to the Pole itself. These words are very similar to those used by the British explorer James Weddell to describe his own experiences in the same area, a month earlier. This has led historians to believe that Morrel may have copied the section from Weddel's.
At 2 pm next day, 15 March, as "Wasp" cruised north-east in the sea that would later bear Weddell's name, Morrell records: "land was seen from the masthead, bearing west, distance 3 leagues" (about nine miles, 14 km). His account continues: "At half past we were close on with the body of land to which Captain Johnson had given the name of New South Greenland". Robert Johnson, a former captain of the "Wasp", had made an exploratory voyage along the western coast of the Antarctic peninsula in 1821. Johnson had called it "New South Greenland". Morrell casually referred to Johnston's description. This indicates that Morrell assumed that the land he was seeing was in fact the east coast of the pensinsula. At the time he wrote this, his position was about 14 degrees east of that pensinsula. The geographical features of the pensinsula were not known at the time of Morrell's voyage. Morrell describes seal hunting activities continuing along this coast during the remainder of the day. On the following morning sealing resumed as the ship moved slowly southward, and continued until Morrell called a halt "because of shortage of water and season far advanced". Mountains of snow, he observed, could be seen about further south.
Morrell turned north from a position he calculated as 67°52'S, 48°11W. Three days later, on , the ship passed what he took to be the northern cape of the land, at 62°41'S, 47°21'W. "This land abounds with oceanic birds of every description", wrote Morrell. He also records seeing 3,000 sea elephants. At 10 o'clock "Wasp" "bade farewell to the cheerless shores of New South Greenland"; there is no further mention of it in the long voyage account. "Wasp" sailed for Tierra del Fuego, then through the Magellan Strait into the Pacific Ocean, reaching Valparaiso, Chile, on 1823.
From the first navigations of the Southern Ocean in the 16th century, lands which subsequently proved to be nonexistent had from time to time been reported in these waters. Polar historian Robert Headland of the Scott Polar Research Institute has suggested various reasons for these false sightings, ranging from "too much rum" to deliberate hoaxes designed to lure rival ships away from good sealing grounds. Some may have been of large ice masses that were carrying rocks and other glacial debris—dirty ice can appear convincingly similar to land. It is also possible that some of these lands existed, but later became submerged after volcanic eruptions. Other sightings may have been of actual land, wrongly located through observational errors due to chronometer failure, bad weather or simple incompetence.
Doubt was cast over the existence of New South Greenland when, in 1838, the French explorer Jules Dumont d'Urville sailed over the position of Morrell's "north cape", but saw no indication of land. This evidence, and the general nature of Morrell's account—its obvious errors, and his reputation as a braggart "as great ... as any hero of autobiographical romance" in the words of British geographer Hugh Robert Mill, led many geographers thereafter to ignore his claims. This scepticism remained even after Sir James Clark Ross reported an appearance of land in 1843, not far from Morrell's alleged observation: Ross's sighting was occasionally proffered as supportive of Morrell's claim. There was no further penetration of the Weddell Sea until 1903, when William Speirs Bruce took "Scotia" to 74°1'S, but in a sector of the sea which did not bring him close to Morrell's or Ross's sightings. Bruce was, however, generally well-disposed towards Morrell, writing that his claims should not be rejected until absolutely disproved.