The air-sea interaction thermodynamics of the western equatorial Pacific, the Earth's largest region of warm SST, is a major component of the global climate system. Along the equator, warm pool thermodynamics and momentum are influenced by equatorial ocean visco-inertial boundary layer dynamics that occur within a few degrees of the equator because of the sign reversal of the Coriolis force. Designed to study this system, COARE Enhanced Monitoring Array (EMA) observations of temperature, salinity, velocity, and surface meteorology were centered at 0, 156°E from February 1992 through April 1994. They sampled variability on the equator over larger space/time-scales than the concurrent Intensive Flux Array (IFA) centered at 2°S, 156°E. The EMA data are examined within the context of the larger scale equatorial Pacific and the El Niño conditions that occurred at that time. There is a structural change in the equatorial Pacific near the dateline resulting from the winds that are strong, steady, and easterly in the east and generally weak, punctuated by westerly wind bursts, in the west. East of the dateline the EUC's speed and transport increases downstream, while in the west it tends to be zonally uniform, consistent with the extra-tropical ocean interior water pathways that tend to converge on the equator east of the dateline. At 0°, 156°E in the western Pacific deep, seasonal upwelling (appearing stronger after the peak of the 1991/92 El Niño than during the following weaker El Niño year) occurs within the thermocline in boreal summer with magnitudes as large as upwelling in the eastern Pacific cold tongue. This large upwelling is associated with large downward turbulent heat flux and large turbulent shear stress. While the inferred mixing is quantitatively inconclusive because of unresolved potential errors, it is consistent with the visco-inertial boundary layer concepts from early theory [e.g. Arthur 1960; Robinson 1960; Stommel 1960; and Charney and Spiegel 1971]. These findings suggest that the equatorial thermodynamics differ from those of the IFA. Further process experimentation is necessary to quantify these results.

This thesis investigated the emission and transport of very short–lived halogens (VSLS) over the tropics. VSLS are described as organic halogen gases with lifetimes of less than 6 months. In areas of rapid convective transport they reach the upper troposphere and lower stratosphere where they contribute to total bromine loading (~20 pptv) in the stratosphere that is a cause of ozone (O3) depletion. This thesis investigated speed of transport in the tropics using model age of air (Chapter 3), the strength of VSLS source regions in tropical troposphere (Chapter 4), and quantification of their monthly emission fluxes (Chapter 5). The two most abundant VSLS bromoform (CHBr3) and CH2Br2 were focussed on. A new model age of air calculation was used to describe transport of ocean emissions in the tropical latitudes. Age of air describes how long an air mass has been out of contact with the emission source region. The two most rapid convection regions of the Indian Ocean (InO) and Western Pacific (WPa) showed age of air in the tropical tropopause layer (TTL) to be 25 days. This is similar to the lifetime of CHBr3 (24 days). Using age of air estimated from simulations covering 1989–2013, it was shown how strong El Niño events can increase the age of air over the WPa by 5–7 days in the mid–troposphere, and up to 12 days in the TTL. This increase in age was due to a change in the Walker Circulation, weakening convection in the WPa and increasing convection over the CPa. Over this period, it was shown that age decreases in the tropical circulation system (the Hadley Cell). Decreasing age results from increasing convection, and more rapid transport of VSLS to the upper troposphere, lower stratosphere (UTLS). To study regional emission sources over the WPa, a tagged CHBr3 and CH2Br2 model was developed. It is the first study to quantify how open and coastal emissions contribute separately to the vertical profiles of CHBr3 and CH2Br2 in the WPa. Variability over the WPa is dominated by an open oceanic emission source, with enhanced coastal emissions influencing concentrations in the upper troposphere. Estimations of 3.14 pptv of CHBr3 and CH2Br2 contribution to TTL Bry were in agreement with recent observational studies (3.27 pptv, Navarro et al. (2015)) over the same region. Comparison with aircraft observations showed that the model has a positive bias and this is attributed to over estimation of model emissions. Ground–based observations were used in an inverse model to estimate surface emissions of CHBr3. This method has not been previously used to estimate CHBr3 emissions. The monthly a posteriori emissions had seasonal cycles in the northern and southern hemisphere coastal emissions, and reductions over tropical open oceans. A posteriori emissions were put in to the model and the predicted volume mixing ratios were able to reproduce ground stations observations over the mid–latitude and tropical stations, important for convective transport of VSLS. The model still showed a bias when compared to CAST and CONTRAST aircraft observations over the Western Pacific, but the mean model minus observed residual was reduced by around 0.3 pptv and 0.1 pptv for respective CAST and CONTRAST campaigns from the a priori emissions.

During the last deglaciation, Greenland ice core records exhibit multiple, high frequency climate events including the Oldest Dryas, Bølling-Allerød and Younger Dryas, which may be linked to meltwater routing of the Laurentide Ice Sheet (LIS). Previous studies show episodic meltwater input, via the Mississippi River to the Gulf of Mexico (GOM) several thousand years before the onset of the Younger Dryas until ~13.0 kcal (thousand calendar) yrs, when meltwater may have switched to an eastern spillway, reducing thermohaline circulation (THC). Data from laminated Orca Basin in the GOM, constrained by 34 Accelerator Mass Spectrometry (AMS) 14C dates, provide the necessary resolution to assess GOM sea-surface temperature (SST) history and test the meltwater routing hypothesis. Paired Mg/Ca and δ18O data on the Foraminifera species Globigerinoides ruber (pink and white varieties) document the timing of meltwater input and temperature change with decadal resolution. White G. ruber SST results show an early 5°C increase at 17.6-16.0 kcal yrs and several SST decreases, including at 16.0-14.7 kcal yrs during the Oldest Dryas (2°C) and at 12.9-11.7 kcal yrs during the Younger Dryas (2.5°C). While the early deglaciation shows strong similarities to records from Antarctica and Tobago Basin, the late deglaciation displays climate events that coincide with Greenland and Cariaco Basin records, suggesting that GOM SST is linked to both northern and southern hemisphere climate. Isolation of the ice-volume corrected δ18O composition of seawater (δ18OGOM) shows multiple episodes of meltwater at ~16.4-15.7 kcal yrs and ~15.2-13.1 kcal yrs with white G. ruber δ18OGOM values as low as -2.5%0. The raw radiocarbon age of the cessation of meltwater in the GOM (11.375±0.40 14C kcal yrs) is synchronous with large changes in tropical surface water Δ14C, a proxy for THC strength. An early meltwater episode beginning at 16.4 kcal yrs during the Oldest Dryas supports the suggestion of enhanced seasonality in the northern North Atlantic during Greenland stadials. We suggest a corollary to the seasonality hypothesis that in addition to extreme winters during stadials, warm summers allowed for LIS melting, which may have enhanced THC slowdown.

In this study, specimens of Tridacna sp., which are reef dwelling bivalve molluscs and have been shown to live up to 60 years, collected from the Huon Peninsula, Papua New Guinea, were sampled for geochemical profiles. The Huon Peninsula is in the heart of the Western Pacific Warm Pool (WPWP), which plays a key role in ENSO dynamics. The uplifted reef terraces of the Huon Peninsula have been extensively studied, and are well dated, which gives the opportunity to reconstruct the local climate of this region at key intervals during the past. Previous work on Tridacna sp. has shown that they precipitate their aragonite shell in equilibrium with the surrounding seawater, and the δ18O profile of a modern T. gigas from the Huon Peninsula has been shown to correlate with precipitation and temperature anomalies, and the Niño 3.4 temperature anomaly record. Fossil samples from this region are therefore assumed to have the ability to capture changes in δ18O attributable to ENSO. Seasonally resolved δ18O measurements from Tridacna sp. from early Holocene and Marine Isotope Stage 3 (MIS3) reefs were used to reconstruct changes in mean climate, seasonality and inter-annual variability (e.g. ENSO). Reconstructions of the mean state tend to agree with previously published studies of Holocene and MIS3 climate, showing similar temperatures to today during the early Holocene, and an average cooling of 2- 3°C during MIS3. The early Holocene Tridacna sp. samples show a reduction in seasonality, consistent with the reduction in seasonal insolation at this time, while those from MIS3 show variable seasonality between 30-60ka. ENSO appears to have been supressed during the early Holocene by up to 50% compared with the late 20th century, which is consistent with coral data and modelling studies. During MIS3, ENSO appears to have been more variable with some records showing anomalous warm and cool events as strong as those seen in the modern T. gigas, used here as a benchmark. Trace element profiles derived from the Tridacna sp. used in this study show a tentative link with temperature and local productivity, but these relationships are subject to species specific and intra-shell effects.

Includes vita. / Title from PDF of title page. / Document formatted into pages; contains 119 pages. / Thesis (Ph.D.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: The air-sea interaction thermodynamics of the western equatorial Pacific, the Earth's largest region of warm SST, is a major component of the global climate system. Along the equator, warm pool thermodynamics and momentum are influenced by equatorial ocean visco-inertial boundary layer dynamics that occur within a few degrees of the equator because of the sign reversal of the Coriolis force. Designed to study this system, COARE Enhanced Monitoring Array (EMA) observations of temperature, salinity, velocity, and surface meteorology were centered at 0, 156°E from February 1992 through April 1994. They sampled variability on the equator over larger space/time-scales than the concurrent Intensive Flux Array (IFA) centered at 2°S, 156°E. The EMA data are examined within the context of the larger scale equatorial Pacific and the El Niño conditions that occurred at that time. / ABSTRACT: There is a structural change in the equatorial Pacific near the dateline resulting from the winds that are strong, steady, and easterly in the east and generally weak, punctuated by westerly wind bursts, in the west. East of the dateline the EUC's speed and transport increases downstream, while in the west it tends to be zonally uniform, consistent with the extra-tropical ocean interior water pathways that tend to converge on the equator east of the dateline. At 0°, 156°E in the western Pacific deep, seasonal upwelling (appearing stronger after the peak of the 1991/92 El Niño than during the following weaker El Niño year) occurs within the thermocline in boreal summer with magnitudes as large as upwelling in the eastern Pacific cold tongue. This large upwelling is associated with large downward turbulent heat flux and large turbulent shear stress. / ABSTRACT: While the inferred mixing is quantitatively inconclusive because of unresolved potential errors, it is consistent with the visco-inertial boundary layer concepts from early theory [e.g. Arthur 1960; Robinson 1960; Stommel 1960; and Charney and Spiegel 1971]. These findings suggest that the equatorial thermodynamics differ from those of the IFA. Further process experimentation is necessary to quantify these results. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Le Pacifique équatorial est une région clé pour l'étude du phénomène climatique El Niño Oscillation Australe (ENSO) qui joue un rôle essentiel sur la variabilité du climat à l'échelle globale. L'objectif de cette thèse est d'étudier, d'une part le rôle des ondes équatoriales sur le mécanisme de Recharge-Décharge d'ENSO et d'autre part, d'observer et comprendre l'impact des couches barrières de sel susceptibles d'influencer ENSO. Le mécanisme de Recharge-Décharge de la bande équatoriale (5°N-5°S) est analysé sur la période 1992-2006 à l'aide de données altimétriques. Les variations de volume d'eau chaude qui rechargent ou déchargent la bande équatoriale sont bien représentées par les transports méridiens de masse exprimés en terme de transports géostrophiques et d'Ekman. Les ondes équatoriales de Rossby premier mode méridien premier mode barocline jouent un rôle important sur la partie géostrophique de ces transports. Une classification des évènements El Niño est également effectuée à l'aide des variations de volume d'eau chaude du Pacifique équatorial. La variabilité de la structure thermohaline de la warm pool est analysée dans la bande équatoriale, à l'aide de données Argo, sur la période 2000-2007. Une validation de ces données ainsi que des tests de différents critères d'estimation des couches barrières de sel sont présentés. Les co-variabilités entre les couches barrières de sel, le front de salinité, les températures de surface et la hauteur dynamique sont analysées. Elles montrent notamment que les températures de surface élevées (SST>28-29°C), associées au maximum de convection atmosphérique sont fortement liées à la présence de couches barrières de sel épaisses (>20m). Les couches barrières de sel sont favorisées par des fortes précipitations, de faibles vents, l'advection zonale de salinité de surface et le cisaillement vertical de courants. Pour la première fois à partir d'observations, l'influence des ondes équatoriales sur les couches barrières de sel est mise en évidenc

Variability in the tropical ocean-atmospheric system causes global scale climate anomalies, most evident in the El Niño-Southern Oscillation’s coupled climate feedbacks. Despite being an area of high interest, many questions still remain regarding the west Pacific warm pool’s response to external forcing, particularly its response to increases in anthropogenic greenhouse gases. Paleoclimate reconstructions coupled with model simulations provide insight into the tropical Pacific’s role in past climate variability necessary to the development of robust climate projections. Most paleoclimate records, however, still lack the resolution, length, and chronological control to resolve rapid variability against a background of orbital-scale variations. Here we present stalagmite oxygen isotope (δ18O) reconstructions from Gunung Mulu National Park (4oN, 115oE ), in northern Borneo, that provide reproducible centennial-scale records of western Pacific hydrologic variability that are precisely U/Th-dated and continuous throughout most of the late Pleistocene (0-160 thousand years ago, kybp). The record comprises an entire glacial-interglacial cycle, which allows us to investigate orbital-scale climate forcings and compare two well-dated glacial terminations in the western tropical Pacific. The ice- volume-corrected δ18O records suggest that glacial boundary condtions, which include significantly lower atmospheric carbon dioxide levels, did not drive significant changes in Mulu rainfall δ18O. Similarly, Borneo stalagmite δ18O is poorly correlated to either global sea level shifts or Sunda Shelf areal exposure is not evident. The Borneo record does vary in phase with local mid-fall equatorial insolation, suggesting that precessional forcing may impart a strong influence on hydroclimate variability in the warm pool. This is best illustrated across Glacial Termination II, when the oscillation of equatorial fall insolation is large and out of phase with ice sheet decay. We also use a subset of well-dated, high-resolution stalagmite δ18O records from Mulu to investigate millennial-scale climate variability during Marine Isotope Stages 3-5 (30-100kybp). We find that regional convection likely decreased during the six massive iceberg discharges defined in the North Atlantic sediment records (“Heinrich events”). The inferred drying (increased stalagmite δ18O) during Heinrich events is consistent with a southward shift of the Intertropical Convergence Zone – the dominant paradigm to explain global climate anomalies originating in the north Atlantic (ref). However, any hydrologic variability related to Dansgaad-Oeschgar (D/O) events, millennial-scale sawtooth temperature anomalies of the last glacial period first evident in the Greenland ice records, is notably absent in the stalagmite records. . The Mulu stalagmite record’s absence of D/O signal, however, is in marked contrast to the regional west Pacific marine records and suggests D/O events and Heinrich events may be characterized by fundamentally different climate mechanisms and feedbacks.

The most important component of the climate system over the Indian Ocean region is the southwest monsoon, which dictates the life and economy of billions of people in the tropics. Being a phenomena that involves interaction between atmosphere, ocean and land, the southwest monsoon is strongly influenced by upper ocean, primarily through warm sea surface temperature (SST). This is particularly true about the southeastern Arabian Sea (SEAS) and the onset of southwest monsoon over the peninsular India. A localized patch of warm water, known as the Arabian Sea mini warm pool (ASMWP), forms in the SEAS during February–March. It remain as the warmest spot in the northern Indian Ocean till early April. A large region, surrounding the SEAS, attains SST exceeding 30°C during April–May, with often the ASMWP as its core. The ASMWP is believed to have a critical impact on the air-sea interaction during the onset phase of southwest monsoon and on the formation of the onset vortex, during late May or early June. This thesis addresses the formation mechanisms of ASMWP, using a high-resolution Ocean General Circulation Model (OGCM) of the Indian Ocean. In addition to the formation of ASMWP, the SEAS is characterized by several features in its hydrography and circulation, which have been invoked in the past to explain the preferential warming of this oceanic region. During November–January, the prevailing surface currents transport low-salinity water from the Bay of Bengal into the SEAS and leads to strong haline stratification in the upper layer and formation of barrier layer (layer between mixed layer and isothermal layer). The vertical distribution of temperature in the SEAS exhibit inversions (higher subsurface temperature than that at surface) during December–February. A high in sea level and anticyclonic eddies develop in the SEAS during December and they propagate westward. These eddies modify the hydrography through downwelling and play an important role in the redistribution of advected low-salinity water within the SEAS. The seasonally reversing coastal and equatorial currents present in and around SEAS also have a major contribution in setting up the hydrography, through the advection and redistribution of cooler low-salinity water. These features make the SEAS a unique oceanographic region. The first hypothesis on the formation of ASMWP, which has been suggested by diagnostic studies, is based on the barrier layer mechanism. The barrier layer, caused by the influx of low-salinity water at surface, is argued to maintain a shallow mixed layer which can warm more efficiently. In addition, presence of barrier layer can prevent mixed layer cooling, by cutting off the interaction of mixed layer with cooler thermocline water below. However, a coupled model study have shown that there is no significant impact on the ASMWP formation from barrier layer, but only a weak warming effect during it mature phase during April. The second hypothesis, which is based on an OGCM study, has suggested that the temperature inversions present within the barrier layer can heat the mixed layer through turbulent entrainment and in turn lead to the formation of ASMWP during February–March. Both hypotheses rule out the possibility of air-sea heat fluxes being the primary reason in its formation. The strong salinity stratification in the SEAS during December–March is central to the hypotheses about formation of the ASMWP. Observational studies have only limited success in assessing the contribution from barrier layer and temperature inversions, as the ASMWP always form in their presence. OGCMs offer a better alternative. However, modelling processes in the northern Indian Ocean, especially that in the SEAS, is a challenging problem. Previous Indian Ocean models have had serious difficulties in simulating the low-salinity water in the Bay of Bengal and its intrusion into the SEAS. The northward advection of low-salinity water in the SEAS, along the west coast of India, is used to be absent in model simulations. Moreover, the coarse resolution inhibited those models from simulating faster surface currents and vigorous eddies as seen in the observations. In this thesis, we use an OGCM of the Indian Ocean, based on the recent version of Modular Ocean Model (MOM4p0), to study the ASMWP. The model has high resolutions in the horizontal (1/4o x 1/4o) and vertical (40 levels, with 5 m spacing in upper 60 m), and has been forced with daily values momentum, heat and freshwater fluxes. The turbulent (latent and sensible) and long wave heat fluxes have been calculated as a function of model SST. The freshwater forcing consists of precipitation, evaporation and river runoff, and there are no surface restoring or flux adjustments. The river runoff has been distributed over several grid points about the river mouth instead of discharging into a singe grid point, which has resulted in remarkable improvements in salinity simulation. The model simulates the Indian Ocean temperature, salinity and circulation remarkably well. The pattern of model temperature distribution and evolution matches very well with that in the observations. Significant improvements have been made in the salinity simulation, including the Bay of Bengal freshwater plume and intrusion of low-salinity water from the bay into the SEAS. The salinity distribution within the SEAS is also well represented in the model. The use of appropriate horizontal friction parameters has resulted in the simulation of realistic currents. The observed features in the SEAS, including the life cycle of the ASMWP, low-salinity water, barrier layer, temperature inversions, eddies and currents are well represented in the model. Present study has unraveled the processes involved in the life cycle of barrier layer and temperature inversions in the SEAS. Presence of low-salinity water is necessary for their formation. Barrier layer develops in the SEAS during November, after the intrusion of low-salinity water from the Bay of Bengal. The barrier layer is thickest during January–February, and it dissipates during March–April. The variations and peak of barrier layer thickness is controlled by variations in isothermal layer depth, which in turn is dominated by the downwelling effects of anticyclonic eddies. The intense solar heating during March–April leads to the formation of shallow isothermal layer and results in the dissipation of barrier layer. Temperature inversions starts developing in the SEAS during December, reaches its peak during January–February and dissipates in the following months. Advection of cooler low-salinity water over warmer salty water and penetrating shortwave radiation is found to cause temperature inversions within the SEAS, whereas winter cooling is also important to the north and south of the SEAS. There is significant variation in the magnitude, depth of occurrence and formation mechanisms of temperature inversions within the SEAS. Analysis of model mixed layer heat budget has shown that the SEAS SST is mainly controlled by atmospheric forcing, including the life cycle of ASMWP. It has also shown that the heating from temperature inversions do not contribute to the formation of ASMWP. In an experiment in which a constant salinity of 35 psu was maintained over the entire model domain, the ASMWP evolved very similar to that in the standard run, suggesting that the salinity effects are not necessary for the formation of ASMWP. Examination of wind field show that the winds over the SEAS during November–February are low due to the blocking of northeasterly winds by Western Ghats. Several process experiments by modifying the wind and turbulent heat fluxforcing fields have shown that these low winds lead to the formation of ASMWP in the SEAS during February–March. The low winds reduce latent heat loss, resulting in net heat gain by the ocean. This helps the SEAS to keep warmer SST while the surrounding region experience intense cooling under the strong dry northeasterly winds. As the winds are weak over the SEAS, the mixed layer is not able to feel the stratification beneath and the mixed layer depth is determined by solar heating, with or without salinity effects. In addition, the weak winds are not able to entrain the temperature inversions present in the barrier layer. The winds are weak during March–April too, and the air-sea heat fluxes dictate the SST evolution during this period. Therefore, during November–April, the SEAS acts as a low wind heat-dominated regime, where the evolution of sea surface temperature is solely determined by atmospheric forcing. We show that, in such regions, the evolution of surface layer temperature is not dependent on the characteristics of subsurface ocean, including the presence of barrier layer and temperature inversions.

Comprendre les mécanismes moteurs et pouvoir anticiper l'impact environnemental du phénomène El Niño Oscillation Australe (ENOA) constituent des enjeux scientifiques et sociétaux de première importance, notamment pour les Pays Emergents. Dans cette thèse, nous avons documenté et contrasté la signature de différents types d'ENOA - dits canoniques et Modoki - pour plusieurs variables climatiques essentielles (température et salinité de surface, niveau de la mer, courant de surface, précipitation, vent de surface, ...), analysé la pertinence de la théorie dite de recharge / décharge, une des quatre théories majeures d'ENOA, à rendre compte ou non de la nature quasi oscillatoire de ces différents types et quantifié l'impact potentiel des modifications des caractéristiques majeures d'ENOA sur notre interprétation des tendances climatiques à 'long' terme pour ces variables climatiques essentielles.

The West Pacific Warm Pool (WPWP) plays an important role in the global heat budget and global hydrologic cycle, so knowledge about its past variability would improve our understanding of global climate. Variations in WPWP precipitation are most notable during El Niño-Southern Oscillation events, when climate changes in the tropical Pacific impact rainfall not only in the WPWP, but around the globe. The stalagmite records presented in this dissertation provide centennial-to-millennial-scale constraints of WPWP precipitation during three distinct climatic periods: the Last Glacial Maximum (LGM), the last deglaciation, and the Holocene. In Chapter 2, the methodologies associated with the generation of U/Th-based absolute ages for the stalagmites are presented. In the final age models for the stalagmites, dates younger than 11,000 years have absolute errors of ±400 years or less, and dates older than 11,000 years have a relative error of ±2%. Stalagmite-specific 230Th/232Th ratios, calculated using isochrons, are used to correct for the presence of unsupported 230Th in a stalagmite at the time of formation. Hiatuses in the record are identified using a combination of optical properties, high 232Th concentrations, and extrapolation from adjacent U/Th dates. In Chapter 3, stalagmite oxygen isotopic composition (d18O) records from N. Borneo are presented which reveal millennial-scale rainfall changes that occurred in response to changes in global climate boundary conditions, radiative forcing, and abrupt climate changes. The stalagmite d18O records detect little change in inferred precipitation between the LGM and the present, although significant uncertainties are associated with the impact of the Sunda Shelf on rainfall d18O during the LGM. A millennial-scale drying in N. Borneo, inferred from an increase in stalagmite d18O, peaks at ~16.5ka coeval with timing of Heinrich event 1, possibly related to a southward movement of the Intertropical Convergence Zone (ITCZ). An inferred precipitation maximum (stalagmite d18O minimum) during the mid-Holocene in N. Borneo supports La Niña-like conditions and/or a southward migration of the ITCZ over the course of the Holocene as likely mechanisms for the observed millennial-scale trends. In Chapter 4, stalagmite Mg/Ca, Sr/Ca, and d13C records reflect hydrologic changes in the overlying karst system that are linked to a combination of rainfall variability and cave micro-environmental effects. Dripwater and stalagmite geochemistry suggest that prior calcite precipitation is a mechanism which alters dripwater geochemistry in slow, stalagmite-forming drips in N. Borneo. Stalagmite Mg/Ca ratios and d13C records suggest that the LGM climate in N. Borneo was drier and that ecosystem carbon cycling may have responded to the drier conditions. Large amplitude decadal- to centennial-scale variability in stalagmite Mg/Ca, Sr/Ca and d13C during the deglaciation may be linked to deglacial abrupt climate change events.