Spatial variations in sea surface temperature (SST) and rainfall changes over the tropics are investigated based on ensemble simulations for the first half of the twenty-first century under the greenhouse gas (GHG) emission scenario A1B with coupled ocean–atmosphere general circulation models of the Geophysical Fluid Dynamics Laboratory (GFDL) and National Center for Atmospheric Research (NCAR). Despite a GHG increase that is nearly uniform in space, pronounced patterns emerge in both SST and precipitation. Regional differences in SST warming can be as large as the tropical-mean warming. Specifically, the tropical Pacific warming features a conspicuous maximum along the equator and a minimum in the southeast subtropics. The former is associated with westerly wind anomalies whereas the latter is linked to intensified southeast trade winds, suggestive of wind–evaporation–SST feedback. There is a tendency for a greater warming in the northern subtropics than in the southern subtropics in accordance ...

Global Warming Pattern Formation: Sea Surface Temperature and Rainfall

A solution is presented for the change in water level in a well of finite diameter after a known volume of water is suddenly injected or withdrawn. A set of type curves computed from this solution permits a determination of the transmissibility of the aquifer.

Response of a finite-diameter well to an instantaneous charge of water. Paper No. H-21

Principles of Isotope Geology

The report summarizes the science of climate change and the impacts of climate change in the United States, now and in the future.

Climate Change Impacts in the United States

..........................................................................................................................................................

/pdf/groundwater-depletion-in-the-united-states-1900-2008-4mrfhw46h1.pdf

Groundwater Depletion in the United States (1900?2008)

This study addresses a need to document changes in streamflow and base flow (groundwater discharge to streams) in Hawaii during the past century. Statistically significant long-term (19132008) downward trends were detected (using the nonparametric MannKendall test) in low-streamflow and base-flow records. These long-term downward trends are likely related to a statistically significant downward shift around 1943 detected (using the nonparametric Pettitt test) in index records of streamflow and base flow. The downward shift corresponds to a decrease of 22% in median streamflow and a decrease of 23% in median base flow between the periods 19131943 and 19432008. The shift coincides with other local and regional factors, including a change from a positive to a negative phase in the Pacific Decadal Oscillation, shifts in the direction of the trade winds over Hawaii, and a reforestation programme. The detected shift and long-term trends reflect region-wide changes in climatic and land-cover factors. A weak pattern of downward trends in base flows during the period 19432008 may indicate a continued decrease in base flows after the 1943 shift. Downward trends were detected more commonly in base-flow records than in high-streamflow, peak-flow, and rainfall records. The decrease in base flow is likely related to a decrease in groundwater storage and recharge and therefore is a valuable indicator of decreasing water availability and watershed vulnerability to hydrologic changes. Whether the downward trends will continue is largely uncertain given the uncertainty in climate-change projections and watershed responses to changes. Copyright (c) 2012 John Wiley & Sons, Ltd.

Trends and shifts in streamflow in Hawai‘i, 1913–2008

Investigation of geochemical indicators to evaluate the connection between inland and coastal groundwater systems near Kaloko-Honokōhau National Historical Park, Hawai‘i

Freshwater-lens thickness and long-term changes in freshwater volume in coastal aquifers are commonly assessed through repeated measurement of salinity profiles from monitor wells that penetrate into underlying salt water. In Hawaii, the thickest measured freshwater lens is currently 262 m in dike-free, volcanic-rock aquifers that are overlain by thick coastal sediments. The midpoint depth (depth where salinity is 50% salt water) between freshwater and salt water can serve as an indicator for freshwater thickness. Most measured midpoints have risen over the past 40 years, indicating a shrinking lens. The mean rate of rise of the midpoint from 1999–2009 varied locally, with faster rates in highly developed areas (1.0 m/year) and slower rates in less developed areas (0.5 m/year). The thinning of the freshwater lenses is the result of long-term groundwater withdrawal and reduced recharge. Freshwater/salt-water interface locations predicted from measured water levels and the Ghyben-Herzberg principle may be deeper than measured midpoints during some periods and shallower during other periods, although depths may differ up to 100 m in some cases. Moreover, changes in the midpoint are slower than changes in water level. Thus, water levels may not be a reliable indicator of the amount of freshwater in a coastal aquifer.

Changes of freshwater-lens thickness in basaltic island aquifers overlain by thick coastal sediments

Simple method for estimating groundwater recharge on tropical islands

Groundwater inundation (GWI) is a particularly challenging consequence of sea-level rise (SLR), as it progressively inundates infrastructure located above and below the ground surface. Paths offlooding byGWIdiffer fromother types of SLRflooding (i.e., wave overwash, storm-drain backflow) such that it ismore difficult tomitigate, and thus requires a separate set of highly innovative adaptation strategies tomanage. To spur consideration ofGWI in planning, data-intensive numericalmodeling methods have been developed that produce locally specific visualizations of GWI, though the accessibility of suchmethods is limited by extensive data requirements. Conversely, the hydrostatic (or ‘bathtub’)modeling approach is widely used in adaptation planning owing to easily accessed visualizations (i.e., NOAASLRViewer), yet its capacity to simulate GWIhas never been tested. Given the separate actions necessary tomitigate GWI relative tomarine overwash, this is a significant gap. Herewe compare a simple hydrostaticmodelingmethodwith amore deterministic, dynamic and robust 3Dnumericalmodeling approach to explore the effectiveness of the hydrostaticmethod in simulating equilibrium aquifer effects ofmulti-decadal sea-level rise, and in turnGWI forHonolulu, Hawai’i.We find hydrostaticmodeling in theHonolulu area and likely other settingsmay yield similar results to numericalmodelingwhen referencing the localmean higher-highwater tide datum (generally typical offlood studies). Thesefindings have the potential to spur preliminary understanding ofGWI impacts inmunicipalities that lack the required data to conduct rigorous groundwater-modeling investigations.We note that themethods explored here forHonolulu do not simulate dynamic coastal processes (i.e., coastal erosion, sediment accretion or changes in land cover) and thus aremost appropriately applied to regions that host heavily armored shorelines behindwhich GWI can develop.

https://iopscience.iop.org/article/10.1088/2515-7620/ab21fe/pdf

Comparison of a simple hydrostatic and a data-intensive 3D numerical modeling method of simulating sea-level rise induced groundwater inundation for Honolulu, Hawai’i, USA

Delwyn S. Oki

Papers

Trends and shifts in streamflow in Hawai‘i, 1913–2008

Investigation of geochemical indicators to evaluate the connection between inland and coastal groundwater systems near Kaloko-Honokōhau National Historical Park, Hawai‘i

Changes of freshwater-lens thickness in basaltic island aquifers overlain by thick coastal sediments

Simple method for estimating groundwater recharge on tropical islands

Comparison of a simple hydrostatic and a data-intensive 3D numerical modeling method of simulating sea-level rise induced groundwater inundation for Honolulu, Hawai’i, USA