Twentieth century sea level: An enigma

Munk, Walter

doi:10.1073/pnas.092704599

Cited by 150 publications

(135 citation statements)

References 29 publications

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“…An influential paper by Munk 36 reviewed the status of closure in the sea-level budget for the 20 th century and reached a number of conclusions. One of these, based on observations and model predictions of changes in Earth rotation, limited the melt contribution from the two ice sheets.…”

Section: The 20 Th Centurymentioning

confidence: 99%

Identifying the causes of sea-level change

et al. 2009

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PrefaceGlobal mean sea-level rise has increased from a rate of a few centimetres per century over the past few millennia to a few decimetres per century in the past few decades. This ten fold increase in rate is due to climate change and is dominated by melting of land ice and warming of ocean water. The current warming trend is expected to continue and so global mean sea level will continue to rise. In this article, we review recent advances in our understanding of past sea-level changes on decadal to millennial timescales to consider how well future changes can be constrained. The majority of studies suggest that global mean sea-level rise will most likely be less than 1 m over the 21 st century. Importantly, there will be significant departures from the global mean by several decimetres in many areas. As a consequence, future research should be targeted at better constraining the spatial variability in future changes so that high-risk areas can be identified. IntroductionWith about 200 million people living within coastal floodplains and 2 million km 2 of land and $1 trillion worth of assets lying less than 1 m above current sea level, sea-level rise is one of the major socio-economic hazards associated with global warming 1 . The expected rate is, however, extremely uncertain. While the latest IPCC report 2 suggests a range of 0.18-0.59 m of sea-level rise between 1980-1999 and 2090-2099, it emphasises that the contribution from ice dynamic changes is highly uncertain and provides three "illustrative" scenarios suggesting a possible addition of up to 0.17 m from this source. Since then, several studies 3,4 have suggested that a rise larger than 1 m cannot be ruled out. Sea-level rates of this magnitude (m per century) are not uncommon in reconstructions of past sea-level change using geological evidence and it has recently been suggested that similar rates occurred during the previous interglacial warm period 120,000 years ago 5,6 when the volume of land ice was similar to that at present.A "headline" figure of 1 m during the 21 st century represents only the global average sealevel rise. Many different physical processes contribute to sea-level change (see Box 1) and none of these produce a spatially uniform signal. Indeed, one of the few statements that can be made with certainty is that future sea-level change will not be the same everywhere. Thus, the development of regional and local estimates of future sea-level rise -required for effective risk assessment -is one of the primary challenges for the coming years 2 . Prediction relies on models, and the veracity of model output is based on verification against historical and geological data.. However, interpretation of these data requires great care in light of the large spatial and temporal variability in sea-level change. In this article we summarise recent progress in understanding the variability in a suite of sea-level related observations at timescales ranging from decades to millennia. We conclude with an estimate of our current ability to predict...

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Section: The 20 Th Centurymentioning

confidence: 99%

Identifying the causes of sea-level change

et al. 2009

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“…Identifying sources of the global rise has been a conundrum, in that estimates of the two predominant sources, steric increases in ocean volume due to thermal expansion and eustatic increases due to melting of ground-based ice only accounts for about half of this estimated increase (Munk 2002;Cazenave and Nerem 2004), although a recent reanalysis (Mitrovica et al 2006) of ancient eclipse, astronomic and geodetic data yields a result that is more consistent with recent observationally-based sea level rise estimates, and suggests that ice melt of approximately 1 mm/year has contributed. Tide gauge records in California and other west coast United States locations that are tectonically stable (Fig.…”

Section: Introductionmentioning

confidence: 99%

Climate change projections of sea level extremes along the California coast

et al. 2008

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California's coastal observations and global model projections indicate thatCalifornia's open coast and estuaries will experience rising sea levels over the next century. During the last several decades, the upward historical trends, quantified from a small set of California tide gages, have been approximately 20 cm/century, quite similar to that estimated for global mean sea level. In the next several decades, warming produced by climate model simulations indicates that sea level rise (SLR) could substantially exceed the rate experienced during modern human development along the California coast and estuaries. A range of future SLR is estimated from a set of climate simulations governed by lower (B1), middle-upper (A2), and higher (A1fi) GHG emission scenarios. Projecting SLR from the ocean warming in GCMs, observational evidence of SLR, and separate calculations using a simple climate model yields a range of potential sea level increases, from 11 to 72 cm, by the 2070-2099 period. The combination of predicted astronomical tides with projected weather forcing, El Niño related variability, and secular SLR, gives a series of hourly sea level projections for 2005-2100. Gradual sea level rise progressively worsens the impacts of high tides, surge and waves resulting from storms, and also freshwater floods from Sierra and coastal mountain catchments. The occurrence of extreme sea levels is pronounced when these factors coincide. The frequency and magnitude of extreme events, relative to current levels, follows a sharply escalating pattern as the magnitude of future sea level rise increases.

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“…This is especially true for lowland estuarine rivers where any rise in sea level can have a far-reaching impact on the community. Over the past century, the global mean sea level has increased by nearly 200 mm [8,9] due to an increase in 20th century ocean heat content [10] and mass increase [11]. The rise rate was found to be accelerating in the past two decades, averaging 3.2 mm per year in a range between 2.8 and 3.6 mm [12].…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal Distributions of Sr and Ba along an Estuarine River with a Large Salinity Gradient to the Gulf of Mexico

2016

Water

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Strontium and barium to calcium ratios are often used as proxies for tracking animal movement across salinity gradients. Many estuarine rivers face saltwater intrusion due to sea level rise, potentially causing changes in mobility and distribution of these metals upstream. From May 2013 to August 2015, monthly water samples were collected and in-situ measurements were performed at six sites along an estuary strongly affected by saltwater intrusion, the Calcasieu River, with salinity ranging from 0.02 to 29.50 Parts Per Thousand (ppt). Results showed that the total Sr concentration and the Sr/Ca ratio both increased significantly with increasing salinity. The average Sr concentration at the site closest to the Gulf of Mexico (Site 6) was 46.21 µmol/L, about 130 times higher than that of the site furthest upstream (Site 1, 0.35). The average Sr/Ca ratio at Site 6 (8.41 mmol/mol) was about three times the average Sr/Ca ratio at Site 1 (2.89). However, the spatial variation in total Ba concentration was marginal, varying from 0.36 to 0.47 µmol/L. The average Ba/Ca ratio at Site 1 (4.82 mmol/mol) was about 54 times the ratio at Site 6 (0.09), showing a negative relation between the Ba/Ca ratio and salinity. All elemental concentrations and ratios had considerable seasonal variations, with significant differences among sampling months for the Sr and Ba concentrations and the Ba/Ca ratio (p < 0.01). The results suggest that for low-gradient estuarine rivers such as the Calcasieu River, water chemistry upstream would experience substantial Sr and Ca enrichment, potentially affecting aquatic environments and biological communities.

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Twentieth century sea level: An enigma

Cited by 150 publications

References 29 publications

Identifying the causes of sea-level change

Identifying the causes of sea-level change

Climate change projections of sea level extremes along the California coast

Spatiotemporal Distributions of Sr and Ba along an Estuarine River with a Large Salinity Gradient to the Gulf of Mexico

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