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Get Information. Open Access Feature Paper Review. Sophie F. Natasha Sekhon. Monica M. Matthew Lachniet. Shading denotes temporal resolution within records given as the time difference between two consecutive stable isotope samples in years. Hiatuses in individual records are shown by blank spaces. Records are arranged by latitude, with lower latitude records at the bottom of Free text dating Buckeye West Virginia panel. Center lines are median values and box hinges represent the first and third quantiles.
Whiskers extend to the highest and lowest values with points plotted beyond the whiskers considered as outliers. Ages solid circles and associated uncertainties are shown with each record. Periods of Northern Hemisphere cooling are highlighted in blue. Records are arranged by latitude. Correlation gXCF strength increases with width of line and depth of color. Blue lines represent positive correlations and red lines represent negative ones. These relationships are computed over the amount of time that each pair of records overlaps, so each relationship covers a slightly different temporal interval within the 10—22 ka window.
Speleothem oxygen isotope records from the Caribbean, Central, and North America reveal climatic controls that include orbital variation, deglacial forcing related to ocean circulation and ice sheet retreat, and the influence of local and remote sea surface temperature variations. Here, we review these records and the global climate teleconnections they suggest following the recent publication of the Speleothem Isotopes Synthesis and Analysis SISAL database. We find that low-latitude records generally reflect changes in precipitation, whereas higher latitude records are sensitive to temperature and moisture source variability.
Tropical records suggest precipitation variability is forced by orbital precession and North Atlantic Ocean circulation driven changes in atmospheric convection on long timescales, and tropical sea surface temperature variations on short timescales. On millennial timescales, precipitation seasonality in southwestern North America is related to North Atlantic climate variability. Great Basin speleothem records are closely linked with changes in Northern Hemisphere summer insolation.
Although speleothems have revealed these critical global climate teleconnections, the paucity of continuous records precludes our ability to investigate climate drivers from the whole of Central and North America for the Pleistocene through modern. This underscores the need to improve spatial and temporal coverage of speleothem records across this climatically variable region.
Introduction Speleothems, or secondary cave carbonates, have become essential tools for the reconstruction of past terrestrial climate variability [ 1 ]. The Speleothem Isotopes Synthesis and Analysis SISAL project and database aims to compile published speleothem data globally to facilitate paleoclimate reconstructions and the evaluation of climate models [ 1 ]. These records were compiled from public archives and published data or provided through correspondence with the original authors. The challenges found while compiling such data are discussed in [ 1 ].
The database archives speleothem oxygen and carbon isotope data, detailed chronologic and analytical information, and important metadata for each cave site and speleothem such as bedrock geology, overburden thickness, and whether cave monitoring was conducted, among other pieces of information that are essential for working with and interpreting speleothem isotope records.
These records cover a vast region, spanning the tropics to mid-latitudes and bordering two oceans, with climate controls that are highly variable both in the modern and through time. Speleothem records from this region have revealed critical climate teleconnections between the polar regions, the tropics, and the mid-latitudes at decadal to orbital timescales [ 3456 ].
Our summary highlights the value, the challenges, and the opportunities afforded by the SISAL compilation of Central and North American and Caribbean speleothem records. Soluble bedrock, including carbonates and evaporites, is present throughout the study region Figure 1with extensive and laterally continuous carbonate deposits stretching across large portions of eastern North and Central America, and smaller, tectonically divided deposits of carbonates and evaporites located to the west.
For the purpose of this paper, we define Central America as the region stretching from the southern border of Panama to the southern border of Mexico, and North America from Mexico northward. As most of Mexico, including the Yucatan Peninsula, is primarily in the zone of tropical influence, monsoon- and ITCZ- related convection, and easterly wind sources, we group records from there together with the other tropical records from Central America and the Caribbean. We group the records from North America that are strongly influenced by westerly wind sources into the North America section, spanning the Southwestern United States northward to the Arctic Ocean.
The climate of western North America is dominated by westerly moisture sources originating from the Pacific Ocean. Precipitation is strongly related to the passage of winter cyclones, which can bring abundant precipitation to the region. The local climate is influenced by the complex topography that generates large gradients in precipitation and temperature [ 12 ]. With the exception of the north Pacific coast, much of western North America can be characterized as arid or semi-arid, with orographic rainout occurring first over the coast ranges, Cascade Range, and the Sierra Nevada and the climate becoming progressively more arid moving inland [ 13 ].
The entire region is also sensitive to droughts influenced by ocean-atmosphere interactions in the tropical Pacific and tropical North Atlantic [ 1415 ]. Much of western North America receives precipitation that is advected zonally over the continent from the north and central Pacific by winter cyclones that originate in the region south of the Aleutian Low and are transported by the westerly winter storm track [ 16 ] Figure 2 A.
Moisture from these winter cyclones can penetrate deeply into western North America, providing the dominant source of precipitation and groundwater recharge from the west coast into the Great Basin [ 17 ], and reaching as far east as central Texas [ 18 ]. However, the most intense rainfall and flooding events along the west coast are often linked to extra-tropical cyclones that derive moisture directly from the central or eastern tropical Pacific.
These systems can develop narrow, concentrated corridors of near-surface water vapor known as atmospheric rivers ARs which are responsible for the warmest and wettest storms reaching the west coast [ 192021 ] Figure 2 A. A study of extreme precipitation events associated with ARs along the California coast suggests they primarily occur during the negative phase of the Arctic Oscillation when the jet stream has a more meridional configuration [ 22 ]. These findings hint at the importance of both high and Free text dating Buckeye West Virginia latitude teleconnections in driving AR occurrence.
Heating of the Mojave and Sonoran deserts in the summer creates a thermal low that draws moisture from the Gulf of California, Gulf of Mexico, and Caribbean Sea into parts of the southwestern United States and northern Mexico [ 24 ]. Most NAM precipitation occurs as isolated thunderstorms or mesoscale convective systems, and thus its influence on modern regional precipitation and its past variability are complex [ 25 ].
The dominant moisture source for monsoon rains varies from west to east, with the Gulf of California and the Pacific providing more moisture to the Mojave and Sonoran deserts and the Gulf of Mexico and Caribbean becoming more important toward the east.
The Great Plains low level jet also carries moisture through eastern Mexico, influencing precipitation in central and northern Mexico, Texas, and into the Great Plains [ 2526 ]. Large-scale ocean-atmosphere interactions strongly influence patterns of precipitation variability in western North America on interannual to decadal timescales. The Pacific Decadal Oscillation PDO is thought to modulate this relationship on decadal timescales, including control on the shape and location of the transitional zone between the of correlation between precipitation and ENSO indices [ 27 ].
The range of this seasonal al is small along the coast and becomes magnified inland [ 30 ]. Analyses of rain and snow isotopes along the coast from central to southern California indicate that moisture source plays an important role in determining precipitation isotopic ratios with subtropical and tropical Pacific sourced moisture leading to precipitation with higher isotope ratios and mid-latitude and north Pacific sourced moisture leading to lower isotope ratios [ 1733 ].
However, McCabe-Glynn et al. Furthermore, isotope-enabled modeling of precipitation isotope als along the west coast of North America suggests that variations in droplet condensation height due to seasonal changes in the polar jet are the primary driver of the observed seasonal al in precipitation isotope ratios [ 3435 ]. Observations and models suggest complex controls on the isotopic al of precipitation in the winter-precipitation dominated region of western North America, and further work is necessary to understand which controls are most important for driving the variations that are transmitted to cave drip waters and ultimately preserved in speleothems.
However, isotopic atures in spring waters and cave drip waters from the Great Basin suggest that the brevity of summer precipitation events, coupled with intense evaporation, limits infiltration of monsoon Free text dating Buckeye West Virginia [ 39 ], indicating that infiltration derived from winter storms is presently the primary source of speleothem growth and suggesting a winter bias for speleothem records [ 540 ].
In southwestern North America, speleothem records from Arizona and New Mexico are interpreted to reflect the balance of contribution of winter relatively depleted in 18 O versus summer relatively enriched in 18 O precipitation, with variations mainly attributed to changing inputs of winter precipitation from the Pacific [ 540 ]. The climate of Eastern North America reflects the confluence of multiple atmospheric processes, primarily driven by the westerlies, Arctic, Gulf of Mexico, and Atlantic sources. The westerlies transport Pacific or western North American air masses across the continent.
The relative influence of these atmospheric sources is in part dictated by the topography of Eastern North America, with the Great Plains area located to the east of the Rockies. The Great Plains is characterized by small mountains to the north, semi-arid climate in the western portion, and increasing humidity to the east [ 54 ].
Further east, the topographic high of the Appalachian Mountains and low of the coastal piedmont regions are characterized by humid summers and winter snowfall in higher altitudes and northern latitudes. During the summer months, the hydroclimate of the eastern North America is dominated by moisture from the Gulf of Mexico and the subtropical Atlantic [ 555657 ]. Transport of lower latitude moisture to continental North America varies with the location and strength of low pressure systems, with steeper pressure gradients resulting in the increased transport of moisture inland [ 56 ].
Winter precipitation occurs when warm air masses from subtropical Atlantic and Gulf of Mexico sources interact with cold air masses from the Pacific and Arctic to produce storms that travel eastward with the polar jet stream [ 55 ]. Winter frontal storms limit the propagation of warm air masses laden with Gulf of Mexico and Atlantic moisture, which are only occasionally able to penetrate to the interior of the continent [ 56 ]. The most intense rainfall and flooding events along the eastern North America are often linked to hurricanes that derive moisture directly from the tropical Atlantic.
These storms gain in intensity across the Western Atlantic and Caribbean and typically move northward along the east coast, or west into the Gulf of Mexico and into the eastern interior of North America, bringing large quantities of rainfall over short periods of time. The Gulf of Mexico is an isotopically enriched source when compared to the more depleted Pacific moisture source.
The climate of Central America and the Caribbean is influenced by the competing effects of Atlantic and Pacific teleconnection patterns. This region includes continental territories, island chains, and mountain ranges of different orientations and elevations, and interactions between this diverse topography and the large-scale Free text dating Buckeye West Virginia produce sub-regional variations in annual rain totals, length of the rainy season and timing of rainfall maxima [ 6970 ].
The Inter-Tropical Convergence Zone ITCZ is the fundamental controlling element of both the Atlantic and the eastern Pacific realms [ 7172 ], and it is the dominant source of rainfall in Central America, particularly south of Guatemala. The meridional oscillation of the ITCZ responds to the seasonal insolation cycle, migrating north during the boreal summer and south during the boreal winter [ 7374 ] Figure 2 A. This seasonal migration produces strong precipitation seasonality in most of Central America, with a pronounced dry season between December and April.
As a consequence, the climate of most of Central America can broadly be classified as dry-winter tropical climate, with comparably small seasonal temperature variations. During boreal summer in the western Caribbean, the CLLJ splits into two branches, with one branch turning northward and transporting moisture to the western Gulf of Mexico, and the southerly branch of the CLLJ continuing westward carrying moisture across the Central American isthmus to the Pacific.
Precipitation on the Caribbean and Gulf of Mexico coasts typically is less seasonal, as easterly trade winds during the winter interact with the mountainous topography to produce orographic rainfall [ 78 ]. On the Pacific slope of southern Mexico, precipitation is advected from the ITCZ, where it is then available for convective systems to produce rainfall in the semi-arid regions of southwestern Mexico. Besides the ITCZ and the NASH, other ificant synoptic influences include the intrusions of polar fronts of midlatitude origin modifying the dry winter and early summer climates of the northern Caribbean and north Central America as well as westward propagating tropical disturbances—a summer season feature associated with enhanced rainfall over the Caribbean [ 70 ].
However, moisture source and air mass rainout history are also important controls on the isotope values of Central American precipitation [ 89 ]. There are 81 published speleothem stable isotope records from Northern and Central America and the Caribbean.
In Central America, identified records would improve representation outside of Mexico e. The Central and North American speleothems show variable levels of dating precision, typically with highest precision dates in high uranium aragonites e. In some cases, generation of precise age models is hampered by dating inversions and large age uncertainties whereas in others the age precision is suitable for decadal-scale climate analysis. As a result, the archived time series have varying levels of uncertainty.
Coverage is densest over the last 50 ka. The representation of speleothem records from different regions across Central and North America varies greatly. High resolution records covering the last years are primarily from the tropics, and include speleothems from Panama, Puerto Rico, Belize, and Mexico Figure 3 b.
However, coverage of the last years is also provided by records from Oregon and at lower temporal resolution in speleothems from Nevada in western North America and West Virginia in eastern North America.Free text dating Buckeye West Virginia
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