Scientists have warned that the global sea level may be rising faster than previously thought.
The research, published in the journal Science, questions the reliability of how sea-level rise in areas such as southern Louisiana in the US is measured.
It further stated that the current measurement method underestimates the severity of the problem. Relative sea-level rise, which is a combination of rising water level and subsiding land, is traditionally measured using tide gauges.
Researchers from Tulane University in the US argue that in coastal Louisiana, tide gauges tell only a part of the story.
The study found that while tide gauges can accurately measure subsidence that occurs below their foundations, they miss out on the shallow subsidence component. With at least 60 per cent of subsidence occurring in the top five metres of the sediment column, tide gauges are not capturing the primary contributor to relative sea-level rise.
An alternative approach is to measure shallow subsidence using surface-elevation tables, inexpensive mechanical instruments that record surface elevation change in wetlands.
The data can then be combined with measurements of deep subsidence from Global Positioning System (GPS) data and satellite measurements of sea-level rise.
Rates of relative sea-level rise obtained from this approach are substantially higher than rates as inferred from tide-gauge data.