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Future extreme sea level seesaws in the tropical Pacific.

Widlansky MJ, Timmermann A, Cai W - Sci Adv (2015)

Bottom Line: Global mean sea levels are projected to gradually rise in response to greenhouse warming.Using present-generation coupled climate models forced with increasing greenhouse gas concentrations and subtracting the effect of global mean sea level rise, we find that climate change will enhance El Niño-related sea level extremes, especially in the tropical southwestern Pacific, where very low sea level events, locally known as Taimasa, are projected to double in occurrence.Additionally, and throughout the tropical Pacific, prolonged interannual sea level inundations are also found to become more likely with greenhouse warming and increased frequency of extreme La Niña events, thus exacerbating the coastal impacts of the projected global mean sea level rise.

View Article: PubMed Central - PubMed

Affiliation: International Pacific Research Center, University of Hawai'i at Mānoa, 1680 East-West Road, Honolulu, HI 96822, USA.

ABSTRACT
Global mean sea levels are projected to gradually rise in response to greenhouse warming. However, on shorter time scales, modes of natural climate variability in the Pacific, such as the El Niño-Southern Oscillation (ENSO), can affect regional sea level variability and extremes, with considerable impacts on coastal ecosystems and island nations. How these shorter-term sea level fluctuations will change in association with a projected increase in extreme El Niño and its atmospheric variability remains unknown. Using present-generation coupled climate models forced with increasing greenhouse gas concentrations and subtracting the effect of global mean sea level rise, we find that climate change will enhance El Niño-related sea level extremes, especially in the tropical southwestern Pacific, where very low sea level events, locally known as Taimasa, are projected to double in occurrence. Additionally, and throughout the tropical Pacific, prolonged interannual sea level inundations are also found to become more likely with greenhouse warming and increased frequency of extreme La Niña events, thus exacerbating the coastal impacts of the projected global mean sea level rise.

No MeSH data available.


Related in: MedlinePlus

Observed sea surface height variability on interannual (top) and annual cycle (bottom) time scales and the corresponding CMIP5 21st-century projections.(A and C) Observed (1979–2013) SD of sea surface height (cm). The red boxes in (A) represent island averaging regions used in Fig. 5. Orange contours in (C) enclose large annual cycle variations in wind stress curl (SD exceeding 3.5 × 10−8 s−1). (B and D) Multimodel projection (22 models that simulate the observed nonlinear relationship between El Niño and the SPCZ) (18) for RCP8.5 (2006–2100) with respect to the historical experiment (1911–2005) for the SD of interannual and annual cycle variability (% change). Stippling denotes regions with no significant change in the multimodel variance according to a two-sample F test (P < 95%) with degrees of freedom specified by either the number of model-years (B, 22 models × 95 years) or model-months (D, 22 models × 12 months), respectively, for interannual and annual cycle changes.
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Figure 2: Observed sea surface height variability on interannual (top) and annual cycle (bottom) time scales and the corresponding CMIP5 21st-century projections.(A and C) Observed (1979–2013) SD of sea surface height (cm). The red boxes in (A) represent island averaging regions used in Fig. 5. Orange contours in (C) enclose large annual cycle variations in wind stress curl (SD exceeding 3.5 × 10−8 s−1). (B and D) Multimodel projection (22 models that simulate the observed nonlinear relationship between El Niño and the SPCZ) (18) for RCP8.5 (2006–2100) with respect to the historical experiment (1911–2005) for the SD of interannual and annual cycle variability (% change). Stippling denotes regions with no significant change in the multimodel variance according to a two-sample F test (P < 95%) with degrees of freedom specified by either the number of model-years (B, 22 models × 95 years) or model-months (D, 22 models × 12 months), respectively, for interannual and annual cycle changes.

Mentions: The largest interannual variability of sea level occurs in the tropical Pacific (Figs. 1 and 2A) and is a well-known aspect of El Niño–Southern Oscillation (ENSO) (1–3) and its interaction with the annual cycle (4–8). During strong El Niño events, such as observed in 1982–1983 and 1997–1998, sea level drops around tropical western Pacific islands by up to 20 to 30 cm (Fig. 1) (9). Such extreme low sea levels expose shallow reefs (referred to in Samoa as “Taimasa,” which means foul-smelling tide) (8, 10), thereby damaging associated coastal ecosystems and contributing to the formation of “flat-topped coral heads” often referred to as microatolls (11). At the same time, sea levels rise in the eastern Pacific—especially along the equator, where anomalies exceeding 35 cm have been recorded around the Galápagos Islands (12)—stressing coastal ecosystems by sea level high stands (13). This Pacific-wide sea level seesaw generally reverses during La Niña, although the anomalies rarely exceed 10 cm (Fig. 1) and coastal impacts are typically less severe (14).


Future extreme sea level seesaws in the tropical Pacific.

Widlansky MJ, Timmermann A, Cai W - Sci Adv (2015)

Observed sea surface height variability on interannual (top) and annual cycle (bottom) time scales and the corresponding CMIP5 21st-century projections.(A and C) Observed (1979–2013) SD of sea surface height (cm). The red boxes in (A) represent island averaging regions used in Fig. 5. Orange contours in (C) enclose large annual cycle variations in wind stress curl (SD exceeding 3.5 × 10−8 s−1). (B and D) Multimodel projection (22 models that simulate the observed nonlinear relationship between El Niño and the SPCZ) (18) for RCP8.5 (2006–2100) with respect to the historical experiment (1911–2005) for the SD of interannual and annual cycle variability (% change). Stippling denotes regions with no significant change in the multimodel variance according to a two-sample F test (P < 95%) with degrees of freedom specified by either the number of model-years (B, 22 models × 95 years) or model-months (D, 22 models × 12 months), respectively, for interannual and annual cycle changes.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4643769&req=5

Figure 2: Observed sea surface height variability on interannual (top) and annual cycle (bottom) time scales and the corresponding CMIP5 21st-century projections.(A and C) Observed (1979–2013) SD of sea surface height (cm). The red boxes in (A) represent island averaging regions used in Fig. 5. Orange contours in (C) enclose large annual cycle variations in wind stress curl (SD exceeding 3.5 × 10−8 s−1). (B and D) Multimodel projection (22 models that simulate the observed nonlinear relationship between El Niño and the SPCZ) (18) for RCP8.5 (2006–2100) with respect to the historical experiment (1911–2005) for the SD of interannual and annual cycle variability (% change). Stippling denotes regions with no significant change in the multimodel variance according to a two-sample F test (P < 95%) with degrees of freedom specified by either the number of model-years (B, 22 models × 95 years) or model-months (D, 22 models × 12 months), respectively, for interannual and annual cycle changes.
Mentions: The largest interannual variability of sea level occurs in the tropical Pacific (Figs. 1 and 2A) and is a well-known aspect of El Niño–Southern Oscillation (ENSO) (1–3) and its interaction with the annual cycle (4–8). During strong El Niño events, such as observed in 1982–1983 and 1997–1998, sea level drops around tropical western Pacific islands by up to 20 to 30 cm (Fig. 1) (9). Such extreme low sea levels expose shallow reefs (referred to in Samoa as “Taimasa,” which means foul-smelling tide) (8, 10), thereby damaging associated coastal ecosystems and contributing to the formation of “flat-topped coral heads” often referred to as microatolls (11). At the same time, sea levels rise in the eastern Pacific—especially along the equator, where anomalies exceeding 35 cm have been recorded around the Galápagos Islands (12)—stressing coastal ecosystems by sea level high stands (13). This Pacific-wide sea level seesaw generally reverses during La Niña, although the anomalies rarely exceed 10 cm (Fig. 1) and coastal impacts are typically less severe (14).

Bottom Line: Global mean sea levels are projected to gradually rise in response to greenhouse warming.Using present-generation coupled climate models forced with increasing greenhouse gas concentrations and subtracting the effect of global mean sea level rise, we find that climate change will enhance El Niño-related sea level extremes, especially in the tropical southwestern Pacific, where very low sea level events, locally known as Taimasa, are projected to double in occurrence.Additionally, and throughout the tropical Pacific, prolonged interannual sea level inundations are also found to become more likely with greenhouse warming and increased frequency of extreme La Niña events, thus exacerbating the coastal impacts of the projected global mean sea level rise.

View Article: PubMed Central - PubMed

Affiliation: International Pacific Research Center, University of Hawai'i at Mānoa, 1680 East-West Road, Honolulu, HI 96822, USA.

ABSTRACT
Global mean sea levels are projected to gradually rise in response to greenhouse warming. However, on shorter time scales, modes of natural climate variability in the Pacific, such as the El Niño-Southern Oscillation (ENSO), can affect regional sea level variability and extremes, with considerable impacts on coastal ecosystems and island nations. How these shorter-term sea level fluctuations will change in association with a projected increase in extreme El Niño and its atmospheric variability remains unknown. Using present-generation coupled climate models forced with increasing greenhouse gas concentrations and subtracting the effect of global mean sea level rise, we find that climate change will enhance El Niño-related sea level extremes, especially in the tropical southwestern Pacific, where very low sea level events, locally known as Taimasa, are projected to double in occurrence. Additionally, and throughout the tropical Pacific, prolonged interannual sea level inundations are also found to become more likely with greenhouse warming and increased frequency of extreme La Niña events, thus exacerbating the coastal impacts of the projected global mean sea level rise.

No MeSH data available.


Related in: MedlinePlus