Sea-Level Rise for the Coasts of California, Oregon, and Washington Past, Present, and Future (2012) / Chapter Skim
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3 Contributions to Global Sea-Level Rise
3 Contributions to Global Sea-Level Rise
Pages 33-54
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From page 33... ...
Because warm biases, reducing estimates of the thermal expansion water expands more than cold water with the same contribution to sea-level rise, and recorded increased amount of heating, and seawater at higher pressure rates of land ice loss. In the most recent estimate, for expands more than seawater at lower pressure, global 19932008, the contribution from land ice increased to sea-level change depends on the distribution of ocean 68 percent, the contribution from thermal expansion temperature change throughout the ocean, from top decreased to 35 percent, and land water storage con- to bottom.
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From page 34... ...
, the using bias-corrected temperature data, and the record contribution of thermal expansion was estimated to has been extended by new observations. In addition, a have increased to 1.5 ± 0.5 mm yr-1 above 700 m and few new estimates of the thermosteric fraction of sea 1.6 ± 0.5 mm yr-1 above 3,000 m, about half of the level have been made using data assimilation products observed rate of global sea-level rise.
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From page 35... ...
for 1993 to 2003. The Argo biases were associated with a particular set Observations for the deep ocean are sparse, so of instruments deployed mainly in the Atlantic Ocean thermal expansion estimates for the full ocean depth (Willis et al., 2009)
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From page 36... ...
(2008; brown line with 1 standard deviation shaded) and an uncorrected estimate down to 1,000 m from the Simple Ocean Data Assimilation model by Carton et al.
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From page 37... ...
d Updated from Leuliette and Willis (2011) for thermosteric sea level.
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From page 38... ...
There are, Different data processing approaches also may however, significant differences between the various account for some differences among thermosteric sea- data assimilation products and direct observations, level estimates, such as the relatively high estimates of arising in part from uncertainties in direct observa TABLE 3.2 Committee Estimates of Thermosteric Sea-Level Rise for the Full Ocean Depth Data Source Used in the Estimate Period Thermosteric Sea-Level Rise Estimates, This Report (mm yr-1) a Ishii and Kimoto (2009)
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From page 39... ...
used Summary a more sophisticated approach, which synthesizes the observed data into a dynamically consistent model The thermal expansion estimates in the IPCC using the adjoint assimilation technique. To ensure Fourth Assessment Report were made before temdynamical consistency, the model forcing fields are perature biases due to the XBT and MBT depth errors modified.
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From page 40... ...
The equivalent of at least and at the base. The difference between accumulation 65 m of sea level is stored in glaciers, ice caps, and ice and ablation is called the mass balance, and it is detersheets.
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From page 41... ...
, by repeated geodetic measurements, by combinations of the two, and by measurements of mass change through gravity surveys using the GRACE satellite system. Quantitative determination of glacier and ice sheet mass balance requires a variety of data sets, including ice surface elevation and ice thickness, the rate of ice flow, and the rate of ice (snow)
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From page 42... ...
Black lines delineate major ice divides. Velocities can reach a few km yr-1 on fast-moving glaciers (e.g., Pine Island)
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From page 43... ...
. The rate of ice loss appears to have increased 0.41 ± 0.08 mm yr-1 for 20032010, but this value does since 1993 because of increasing surface melt on the not include the glaciers and ice caps on the periphery of Greenland Ice Sheet and faster flow of some outlet the Greenland and Antarctic ice sheets.
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From page 44... ...
used GRACE gravity methods to deter- terrestrial groundwater signal through modeling. mine ice losses from high mountain Asia and estimated All glacier and ice cap loss rates reported to date that the sea-level contribution of the entire region was are based on a global glacier and ice cap inventory 0.13 ± 0.04 mm yr-1 SLE for 20032009.
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From page 45... ...
Approximately one-third of the uninventoried area is in the peripheral glaciers and ice caps surrounding the two ice sheets, and most of the rest is in North America. "Missing" indicates that data are absent in the Cogley (2009)
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From page 46... ...
age loss rates for 20022009 were 0.56 ± 0.13 mm yr-1 Such information is not always available or presented for the Greenland Ice Sheet and 0.37 ± 0.14 mm yr-1 for in a useful way. In this sense, the best mass balance the Antarctic Ice Sheet.
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From page 47... ...
(2009) 20002008 Mass balance method 0.46 20032008 0.66 Antarctic Ice Sheet IPCC (2007)
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this period (Rasmussen et al., 2011, corrected here for The ice sheets are so thick (Figures 3.6 and 3.7) that ice already grounded below sea level)
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From page 49... ...
prior to 2007. The new estimates of the glacier and Since about 2006, the rate of ice loss in Greenland ice cap contribution to sea-level rise tend to be at the has increased substantially and the rate of change in high end of the estimates provided in the IPCC Fourth Antarctica, while more difficult to quantify, appears to Assessment Report (Table 3.3)
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From page 50... ...
In the most recent periods reported, wide range of spatial and temporal scales involved, fully the loss rates are 0.56 ± 0.13 mm yr-1 from 2002 to deterministic models are generally not used. A variety 2009 for the Greenland Ice Sheet, 0.37 ± 0.14 mm yr-1 of nondeterministic approaches have been developed from 2002 to 2009 for the Antarctic Ice Sheet, and (Eagleson, 1994; Famiglietti et al., 2009)
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From page 51... ...
Recent Advances The terrestrial hydrologic processes contributing to Reservoir Storage sea-level change remain poorly constrained, although the importance of water storage in artificial reservoirs Until recently, additions to sea level from groundhas become increasingly clear. Apart from changes in water extraction were thought to be largely offset by precipitation patterns and land ice volume, the primary increasing reservoir storage, although few studies esterrestrial water fluxes are now thought to be reservoir timated uncertainties in reservoir storage.
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From page 52... ...
Although more Other Contributors data (e.g., GRACE) and model results are available now than were for the IPCC Fourth Assessment Re Snow accumulation and loss dominate seasonal port, it remains difficult to constrain the contributions variations in the terrestrial water contribution to global of terrestrial water to sea-level rise and uncertainties mean sea level but do not contribute to a long-term are large.
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From page 53... ...
Since 2006, ice loss rates have accelerated in the ice sheets and declined in CONCLUSIONS glaciers and ice caps, likely reflecting interannual to multi-annual variability and possibly uncertainties The most comprehensive recent assessments of in data processing or interpretation of short records. global sea-level rise is given in the IPCC Fourth The most recent published estimate is that land ice Assess ment Report, which evaluated data and research melt accounted for about 65 percent of global sea-level results published up to about mid-2006, and Church et rise for 19932008 (Church et al., 2011)
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