Thomas Lempriere and James Clark Ross carved a sandstone marker on Tasmania's Isle of the Dead, one of the oldest benchmarks for measuring sea level rise.

Thomas James Lempriere was a British colonial administrator in the Australian colony of Van Diemen's Land. He is known for his diaries depicting the convict period in Van Diemen's Land, his work as a portrait and landscape painter, and his work as a pioneering naturalist.

Rear-Admiral of the Red Sir James Clark Ross was a Royal Navy officer and explorer who explored both the North and South Poles. In the Arctic, he participated in two expeditions led by his uncle, John Ross, and in four led by William Edward Parry: in the Antarctic, he led his own expedition from 1839 to 1843.

Isle of the Dead is an island, about 1 hectare in area, adjacent to Port Arthur, Tasmania, Australia. It is historically significant since it retains an Aboriginal coastal shell midden, one of the first recorded sea-level benchmarks, and one of the few preserved Australian convict-period burial grounds. The Isle of the Dead occupies part of the Port Arthur Historic Site, is part of Australian Convict Sites and is listed as a World Heritage Property because it represents convictism in the era of British colonisation.

The sea level has been rising from the end of the last ice age, which was around 20,000 years ago. Between 1901 and 2018, the average sea level rose by 15–25 cm (6–10 in), with an increase of 2.3 mm (0.091 in) per year since the 1970s. This was faster than the sea level had ever risen over at least the past 3,000 years. The rate accelerated to 4.62 mm (0.182 in)/yr for the decade 2013–2022. Climate change due to human activities is the main cause. Between 1993 and 2018, melting ice sheets and glaciers accounted for 44% of sea level rise, with another 42% resulting from thermal expansion of water.