[1] Several proxies have been developed to reconstruct past sea-surface temperature (SST) but different proxies may reflect temperatures of different seasons and each proxy is characterized by certain uncertainties. Therefore, a multi-proxy approach is preferred to precisely reconstruct SST. Here, we reconstruct SST of the ocean offshore southeastern Australia (Murray Canyons area) for the last ~135 ka using three independent organic proxies (TEX^H₈₆ based on glycerol dialkyl glycerol tetraethers (GDGTs), U^K’₃₇ based on alkenones and LDI based on long-chain diols) in addition to foraminiferal faunal assemblages. The organic proxy records show similar trends, with highest temperature (21 °C for U^K’₃₇ and TEX^H₈₆, and 25 °C for LDI) during the last interglacial and lowest temperature (8 °C for TEX^H₈₆, 10 °C for U^K’₃₇ and 12 °C for LDI) during the Last Glacial Maximum. However, the differences in absolute SST estimates obtained by the organic proxies varied over time with differences of up to 9 °C between LDI and TEX^H₈₆. The seasonal SST reconstructions based on the modern analogue of foraminiferal assemblages also show similar trends as the organic proxies with highest temperatures during the last interglacial (23 °C for the warmest month SST, 20 °C for mean annual and 18 °C for the coolest month) and lowest temperature during the last glacial maximum (14 °C for the warmest month, 11 °C for mean annual and 9 °C for the coolest month). Down core comparison between the reconstructed SSTs of the organic and inorganic proxies shows that LDI inferred-temperatures compare well with the temperature of the warmest month, TEX^H₈₆ with the temperature of the coolest month and U^K’₃₇ with mean annual temperature. An increase in TEX^H₈₆ SST estimates relative to those of other proxies during deglaciations and interglacials suggest that either winter temperatures rapidly warmed, possibly due to an invigoration of the Leeuwin Current over the core site, or that there was a change in the growth season of the Thaumarchaeota, the source organism of GDGTs. Our study shows the benefits of a multi-proxy approach in the interpretation of SST proxies, leading to a more robust knowledge of past ocean temperature changes.

[1] Biweekly sediment trap samples and concurrent hydrographic measurements collected between March 2005 and October 2008 from the Cariaco Basin, Venezuela are used to assess the relationship between [CO₃^2-] and the area densities (ρ_A) of two species of planktonic foraminifera (Globigerinoides ruber (pink) and Globigerinoides sacculifer). Calcification temperatures were calculated for each sample using species-appropriate oxygen isotope (δ¹⁸O) temperature equations that were then compared to monthly temperature profiles taken at the study site in order to determine calcification depth. Ambient [CO₃^2-] was determined for these calcification depths using alkalinity, pH, temperature, salinity, and nutrient concentration measurements taken during monthly hydrographic cruises. ρ_A, which is representative of calcification efficiency, is determined by dividing individual foraminiferal shell weights (± 0.43 µg) by their associated silhouette areas and taking the sample average. The results of this study show a strong correlation between ρ_A and ambient [CO₃^2-] for both G. ruber and G. sacculifer (R² = 0.89 and 0.86 respectively), confirming that [CO₃^2-] has a pronounced effect on the calcification of these species. Though the ρ_A for both species reveal a highly significant (p < 0.001) relationship with ambient [CO₃^2-], linear regression reveals that the extent to which [CO₃^2-] influences foraminiferal calcification is species-specific. Hierarchical regression analyses indicate that other environmental parameters (temperature and [PO₄^3-]) do not confound the use of G. ruber and G. sacculifer ρ_A as a predictor for [CO₃^2-]. This study suggests that G. ruber and G. sacculifer ρ_A can be used as reliable proxies for past surface ocean [CO₃^2-].

[1] To what extent are individual middle Miocene eccentricity-scale benthic foraminiferal carbon isotope maxima (so-called CM events) related to changes in marine export productivity? Here we use benthic foraminiferal accumulation rates (BFAR) from three sites in the Pacific and Southern Ocean and a geochemical box model to assess relationships between benthic foraminiferal δ¹³C records, export productivity, and the global carbon cycle. Results from Deep Sea Drilling Project Hole 588 and Ocean Drilling Program Site 747 show a distinct productivity maximum during CM 6 at 13.8 Ma, the time of major expansion of ice on Antarctica. Productivity maxima during other CM events are only recorded at high latitude Site 747. A set of numerical experiments tests whether changes in foraminiferal δ¹³C records (CM events) and export productivity can be simulated solely by sea level fluctuations and the associated changes in global weathering-deposition cycles, by sea level fluctuations plus global climatic cooling, and by sea level fluctuations plus invigorated ocean circulation. Consistent with data, the periodic forcing of sea level and albedo (and associated weathering cycles) produce δ¹³C variations of the correct temporal spacing, albeit with a reduced amplitude. A productivity response of the correct magnitude is achieved by enhancing ocean circulation during cold periods. We suggest that the pacing of middle Miocene δ¹³C fluctuations is associated with cyclical sea level variations. The amplitude, however, is muted perhaps due to the competing effects of a time-lagged response to sea level low stands but an immediate response to invigorated ocean circulation during cold phases.

[1] Antarctic Intermediate Water (AAIW) and Subantarctic Mode Water (SAMW) are the main conduits for the supply of dissolved silicon (silicic acid) from the deep Southern Ocean to the low latitude surface ocean, and therefore have an important control on low latitude diatom productivity. Enhanced supply of silicic acid by AAIW (and SAMW) during glacial periods may have enabled tropical diatoms to outcompete carbonate-producing phytoplankton, decreasing the relative export of inorganic to organic carbon to the deep ocean and lowering atmospheric pCO₂. This mechanism is known as the ‘Silicic Acid Leakage Hypothesis’ (SALH). Here we present records of neodymium and silicon isotopes from the western tropical Atlantic that provide the first direct evidence of increased silicic acid leakage from the Southern Ocean to the tropical Atlantic within AAIW during glacial Marine Isotope Stage (MIS) 4 (~60–70 ka). This leakage was approximately coeval with enhanced diatom export in the NW Atlantic and across the eastern equatorial Atlantic and provides support for the SALH as a contributor to CO₂ drawdown during full glacial development.

[1] In situ measurements of Mg/Ca, Zn/Ca, Mn/Ca and Ba/Ca in Globigerinoides bulloides and Globigerina ruber from Southwest Pacific core top sites and plankton tow are reported and their potential as paleo-proxies explored. The modern samples cover 20° of latitude from 34-54°S, 7–19 °C water temperature, and variable influence of subantarctic (SAW) and subtropical (STW) surface waters. Trace element signatures recorded in core top and plankton tow planktic foraminifera are examined in the context of the chemistry and nutrient profiles of their modern water masses. Our observations suggest that Zn/Ca and Mn/Ca may have potential to trace SAW and STW. Intra- and inter-species offsets identified by in situ measurements of Mg/Ca and Zn/Ca indicate these ratios may also record changes in thermal and nutrient stratification in the upper ocean.

[2] We apply these potential proxies to fossilised foraminifera from the high resolution core MD97-2121.At the Last Glacial Maximum surface water Mg/Ca-temperature estimates indicate that temperatures were ca.6-7 °C lower than present, accompanied by low levels of Mn/Ca and Zn/Ca and minimal thermal and nutrient stratification. This is consistent with regional dominance of SAW and reduced STW inflow associated with a reduced South Pacific Gyre (SPG). Upper ocean thermal and nutrient stratification collapsed during the Antarctic Cold Reversal, before poleward migration of the zonal winds and ocean fronts invigorated the SPG and increased STW inflow in the early Holocene.Together with reduced winds, this favoured a stratified upper ocean from ca.10 ka to present.

[1] Guaymas Basin, Gulf of California, is a restricted basin located under the present-day wet/dry subtropical divide (~27ºN) and is ideally circumstanced for detecting variations in the North Pacific Subtropical High (NPSH)/Trade Wind system.

[2] Controlled by climate cell boundary displacement, NPSH midwinter location was the primary influence on timing and intensity of upwelling seasons in Guaymas Basin. Analysis of high-resolution X-ray fluoresence data and sediment fabric log from 75% laminated Core MD02-2517/2515, western Guaymas Basin, reveals systematic changes in NPSH behavior over the last ~55 kyr BP. Southward displacement of the wet/dry subtropical divide controlled upwelling-related diatom productivity, while sea level and regional rainfall controlled terrigenous supply. The basin was oxic during the glacial and preservation was ensured by high burial rate due to the increased deposition of terrigenous sediment. Sediment fabric style (number and/or thickness of laminae, plus color-banding and homogeneous intervals) changes systematically through the core and gives insights into the number of seasons occurring in Guaymas Basin, and the occurrence and intensity of the upwelling season. Five millennial-scale low flux events with close timing to Heinrich events, and ten decadal/centennial-scale low biogenic silica events occurring in the interval ~33–16.5000 years Before Present (kyr BP), are interpreted as times of extreme aridity. At ~16.5 kyr BPa regime shift from terrigenous-dominated oxic to evenly balanced biogenic-terrigenous dysoxic conditions occurred. Although there was a further extreme arid event at ~11.5 kyr BP, ~16.5 kyr BP was essentially the beginning of the interglacial.

[1] The initial rise in atmospheric CO₂ during the last deglaciation was likely driven by input of carbon from a ¹³C-depleted reservoir [Schmitt et al., 2012]. Here we show that high resolution benthic foraminiferal records from the mid-depth Brazil Margin display an abrupt drop in δ¹³C during Heinrich Stadial 1 (HS1) that is similar to but larger than in the atmosphere. Comparing the Brazil Margin results to published records from the North Atlantic, we are unable to account for the South Atlantic δ¹³C data with conservative mixing between northern and southern component water masses. Rapid input of abyssal water from the Southeast Atlantic could account for deglacial δ¹³C anomalies at the Brazil Margin but it would require a reversal in deep water flow direction compared to today. A new mid-depth water mass may explain similar HS1 δ¹³C values in both the North and South Atlantic, but contrasting oxygen isotopic values between the two basins do not support the presence of a single dominant water mass at mid-depths. Instead, it appears that δ¹³C behaved non-conservatively during the deglaciation, possibly reflecting the input of carbon from an isotopically depleted source.

[1] A sediment core from the West Spitsbergen continental margin was studied to reconstruct climate and paleoceanographic variability during the last ~9 ka in the eastern Fram Strait (FS). Our multiproxy evidence suggests that the establishment of the modern oceanographic configuration in the eastern FS occurred stepwise, in response to the postglacial sea-level rise and the related onset of modern sea-ice production on the shallow Siberian shelves. The late Early and Mid-Holocene interval (9 to 5 ka) was generally characterized by relatively unstable conditions. High abundance of the subpolar planktic foraminifer species Turborotalita quinqueloba implies strong intensity of Atlantic Water (AW) inflow with high productivity and/or high AW temperatures, resulting in a strong heat flux to the Arctic. A series of short-lived cooling events (8.2, 6.9, and 6.1 ka) occurred superimposed on the warm late Early to Mid-Holocene conditions. Our proxy data imply that simultaneous to the complete postglacial flooding of Arctic shallow shelves and the initiation of modern sea-ice production, strong advance of polar waters initiated modern oceanographic conditions in the eastern FS at ~5.2 ka. The Late Holocene was marked by the dominance of the polar planktic foraminifer species Neogloboquadrina pachyderma, a significant expansion of sea ice/icebergs, and strong stratification of the water column. Although planktic foraminiferal assemblages as well as sea subsurface temperatures suggest a return of slightly strengthened advection of subsurface AW after 3 ka, a relatively stable cold-water layer prevailed at the sea surface, and the study site was probably located within the seasonally fluctuating marginal ice zone during the Neoglacial period.

[1] The North Atlantic and Norwegian Sea are prominent sinks of atmospheric CO₂ today, but their roles in the past remain poorly constrained. In this study, we attempt to use B/Ca and δ¹¹B ratios in the planktonic foraminifera Neogloboquadrina pachyderma (sinistral variety) to reconstruct subsurface water pH and pCO₂ changes in the polar North Atlantic during the last deglaciation. Comparison of core-top results with nearby hydrographic data shows that B/Ca in N. pachyderma (s) is mainly controlled by seawater B(OH)₄⁻/HCO₃⁻ with a roughly constant partition coefficient of 1.48 ± 0.15 × 10⁻³ (2σ), and δ¹¹B in this species is offset below δ¹¹B of the borate in seawater by 3.38 ± 0.71‰ (2σ). These values represent our best estimates with the sparse available hydrographic data close to our core-tops. More culturing and sediment trap work is needed to improve our understanding of boron incorporation into N. pachyderma (s). Application of a constant K_D of 1.48 × 10⁻³ to high resolution N. pachyderma (s) B/Ca records from two adjacent cores off Iceland shows that subsurface pCO₂ at the habitat depth of N. pachyderma (s) (~50 m) generally followed the atmospheric CO₂ trend but with negative offsets of ~10–50 ppmv during 19–10 ka. These B/Ca-based reconstructions are supported by independent estimates from low-resolution δ¹¹B measurements in the same cores. We also calibrate and apply Cd/Ca in N. pachyderma (s) to reconstruct nutrient levels for the same down cores. Like today's North Atlantic, past subsurface pCO₂ variability off Iceland was significantly correlated with nutrient changes that might be linked to surface nutrient utilization and mixing within the upper water column. Because surface pCO₂ (at 0 m water depth) is always lower than at deeper depths and if the application of a constant K_D is valid, our results suggest that the polar North Atlantic has remained a CO₂ sink during the calcification seasons of N. pachyderma (s) over the last deglaciation.

[1] The Eocene-Oligocene (E/O) boundary interval marks one of the largest and most rapid changes in climate during the last 50 Myr. Because of a very shallow calcium carbonate compensation depth in the Eocene, as well as the reworking of sediments and hiatuses in the boundary zone, it has also been one of the most difficult stratigraphic boundaries to study in deep water marine sections, especially in the Pacific Ocean. Recently, three drill sites have recovered complete sections of the E/O boundary interval in the tropical Pacific. A detailed study of these sections shows a series of pulses of reworked older radiolarians in the upper Eocene and lowermost Oligocene. The two largest pulses are coincident with the two sharp steps in carbon and oxygen isotope values that bracket the E/O boundary. Several smaller peaks in reworked material precede these two maxima. It is proposed that immixing of the older radiolarian species results from erosion and redeposition, possibly linked to pulses of new bottom water formation and the formation of a deep pycnocline.

[1] The strength and latitudinal position of the North Atlantic Current, NAC, determines the position of the Arctic front and heat transport to the high northern latitudes with potentially important consequences for Northern Hemisphere glaciation. A southward shift in the NAC and reduced poleward heat transport is hypothesized to have triggered the last major climate transition in Earth's history—late Pliocene intensification of Northern Hemisphere glaciation (iNHG). In turn, iNHG is hypothesized to have led to the amplification of climate variability on suborbital time scales. To date, however, only a handful of adequately resolved records are available to test these two hypotheses. Here we present a new late Pliocene to earliest Pleistocene record from Integrated Ocean Drilling Program Site U1313 (North Atlantic, 41°N; 2.9 to 2.4 Ma). We use Mg/Ca-derived paleotemperature records in planktic foraminiferal calcite to investigate changes in summer sea-surface temperatures (SST) on orbital and suborbital time scales. Our results call into question the suggestion that significant weakening and/or southward shift of the NAC served as a trigger for Northern Hemisphere cooling and intensified continental ice sheet growth across iNHG. In contrast to the late Pleistocene, during iNHG, we find that the position of the NAC and Arctic Front probably lay well to the north of Site U1313 and that the amplitude of suborbital SST variability did not change on glacial-interglacial time scales. Conservative estimates of Late Pliocene to earliest Pleistocene interglacial summer SSTs in our record are up to 3°C warmer than present, while glacial summer SSTs are only 2°C to 3°C cooler. In fact, our interglacial summer SSTs are remarkably similar to those of the mid-Pliocene. Our findings indicate that iNHG must have involved amplifying feedback mechanisms that are tightly coupled to ice sheet growth but that these processes were insufficiently developed by the late Pliocene/earliest Pleistocene to have triggered large amplitude changes in suborbital climate in the midlatitude North Atlantic.

[1] Six Ocean Drilling Program (ODP) sites, in the Northwest Atlantic have been used to investigate kinematic and chemical changes in the “Western Boundary Undercurrent” (WBUC) during the development of full glacial conditions across the Marine Isotope Stage 5a/4 boundary (~70,000 years ago). Sortable silt mean grain size measurements are employed to examine changes in near bottom flow speeds, together with carbon isotopes measured in benthic foraminifera and % planktic foraminiferal fragmentation as proxies for changes in water-mass chemistry. A depth transect of cores, spanning 1.8–4.6 km depth, allows changes in both the strength and depth of the WBUC to be constrained across millennial scale events. measurements reveal that the flow speed structure of the WBUC during warm intervals (“interstadials”) was comparable to modern (Holocene) conditions. However, significant differences are observed during cold intervals, with higher relative flow speeds inferred for the shallow component of the WBUC (~2 km depth) during all cold “stadial” intervals (including Heinrich Stadial 6), and a substantial weakening of the deep component (~3–4 km) during full glacial conditions. Our results therefore reveal that the onset of full glacial conditions was associated with a regime shift to a shallower mode of circulation (involving Glacial North Atlantic Intermediate Water) that was quantitatively distinct from preceding cold stadial events. Furthermore, our chemical proxy data show that the physical response of the WBUC during the last glacial inception was probably coupled to basin-wide changes in the water-mass composition of the deep Northwest Atlantic.

[1] We present a new hypothesis to explain the millennial-scale temperature variability recorded in ice cores known as Dansgaard-Oeschger (DO) cycles. We propose that an ice shelf acted in concert with sea ice to set the slow and fast timescales of the DO cycle, respectively. The abrupt warming at the onset of a cycle is caused by the rapid retreat of sea ice after the collapse of an ice shelf. The gradual cooling during the subsequent interstadial phase is determined by the timescale of ice-shelf regrowth. Once the ice shelf reaches a critical size, sea ice expands, driving the climate rapidly back into stadial conditions. The stadial phase ends when warm subsurface waters penetrate beneath the ice shelf and cause it to collapse. This hypothesis explains the full shape of the DO cycle, the duration of the different phases, and the transitions between them and is supported by proxy records in the North Atlantic and Nordic Seas.

[1] Available overwash records from coastal barrier systems document significant variability in North Atlantic hurricane activity during the late Holocene. The same climate forcings that may have controlled cyclone activity over this interval (e.g., the West African Monsoon, El Niño–Southern Oscillation (ENSO)) show abrupt changes around 6000 yrs B.P., but most coastal sedimentary records do not span this time period. Establishing longer records is essential for understanding mid-Holocene patterns of storminess and their climatic drivers, which will lead to better forecasting of how climate change over the next century may affect tropical cyclone frequency and intensity. Storms are thought to be an important mechanism for transporting coarse sediment from shallow carbonate platforms to the deep-sea, and bank-edge sediments may offer an unexplored archive of long-term hurricane activity. Here, we develop this new approach, reconstructing more than 7000 years of North Atlantic hurricane variability using coarse-grained deposits in sediment cores from the leeward margin of the Great Bahama Bank. High energy event layers within the resulting archive are (1) broadly correlated throughout an offbank transect of multi-cores, (2) closely matched with historic hurricane events, and (3) synchronous with previous intervals of heightened North Atlantic hurricane activity in overwash reconstructions from Puerto Rico and elsewhere in the Bahamas. Lower storm frequency prior to 4400 yrs B.P. in our records suggests that precession and increased NH summer insolation may have greatly limited hurricane potential intensity, outweighing weakened ENSO and a stronger West African Monsoon—factors thought to be favorable for hurricane development.

[1] Understanding changes in export production through time provides insight into the response of the biological pump to global climate change, particularly during periods of rapid climate change. In this study we consider what role changes in export production may have had on carbon sequestration and how this may have contributed to the onset of the Eocene-Oligocene transition (EOT). In addition, we consider if these export production variations are dominantly controlled by orbitally driven climate variability. To accomplish these objectives, we report changes in export production in the Eastern Equatorial Pacific (EEP) from Site U1333 across the EOT reconstructed from a high-resolution record of marine barite accumulation rates (BAR). BAR fluctuations suggest synchronous declines in export production associated with the two-step increases in oxygen isotopes that define the transition. The reduction in productivity across the EOT suggests that the biological pump did not contribute to carbon sequestration and the cooling over this transition. We also report a previously undocumented peak in EEP export productivity before the EOT onset. This peak is consistent with export production proxies from the Southern Ocean, potentially implying a global driver for this precursor event. We propose that this enhanced export production and the associated carbon sequestration in the late Eocene may have contributed to the pCO₂ drawdown at the onset of Antarctic glaciation.

[1] During the six Heinrich events of the last 70 kyr, episodic calving from the circum-Atlantic ice sheets released large numbers of icebergs into the North Atlantic. These icebergs and associated meltwater flux are hypothesized to have led to a shutdown of Atlantic Meridional Overturning Circulation and severe cooling in large parts of the Northern Hemisphere. However, due to the limited availability of high-resolution records, the magnitude of sea surface temperature (SST) changes related to the impact of Heinrich events on the midlatitude North Atlantic is poorly constrained. Here we present a record of -based SSTs derived from sediments of Integrated Ocean Drilling Project Site U1313, located at the southern end of the ice-rafted debris (IRD) belt in the midlatitude North Atlantic (41°N). We demonstrate that all six Heinrich events are associated with a rapid warming of surface waters by 2–4°C in a few thousand years. The presence of IRD leaves no doubt about the simultaneous timing and correlation between rapid surface water warming and Heinrich events. We argue that this warming in the midlatitude North Atlantic is related to a northward expansion of the subtropical gyre during Heinrich events. As a wide range of studies demonstrated that in the central IRD belt Heinrich events are associated with low SSTs, these results thus identify an antiphased (seesaw) pattern in SSTs during Heinrich events between the midlatitude (warm) and northern North Atlantic (cold). This highlights the complex response of surface water characteristics in the North Atlantic to Heinrich events that is poorly reproduced by freshwater hosing experiments and challenges the widely accepted view that, within the IRD belt of the North Atlantic, Heinrich events coincide with periods of low SSTs.

[1] Past water column stratification can be assessed through comparison of the δ¹⁸O of different planktonic foraminiferal species. The underlying assumption is that different species form their shells simultaneously, but at different depths in the water column. We evaluate this assumption using a sediment trap time-series of Neogloboquadrina pachyderma (s) and Globigerina bulloides from the NW North Atlantic. We determined fluxes, δ¹⁸O and δ¹³C of shells from two size fractions to assess size-related effects on shell chemistry and to better constrain the underlying causes of isotopic differences between foraminifera in deep-sea sediments. Our data indicate that in the subpolar North Atlantic differences in the seasonality of the shell flux, and not in depth habitat or test size, determine the interspecies Δδ¹⁸O. N. pachyderma (s) preferentially forms from early spring to late summer, whereas the flux of G. bulloides peaks later in the season and is sustained until autumn. Likewise, seasonality influences large and small specimens differently, with large shells settling earlier in the season. The similarity of the seasonal δ¹⁸O patterns between the two species indicates that they calcify in an overlapping depth zone close to the surface. However, their δ¹³C patterns are markedly different (>1‰). Both species have a seasonally variable offset from δ¹³C_DIC that appears to be governed primarily by temperature, with larger offsets associated with higher temperatures. The variable offset from δ¹³C_DIC implies that seasonality of the flux affects the fossil δ¹³C signal, which has implications for reconstruction of the past oceanic carbon cycle.

[1] We estimate an identified cointegrated vector autoregression model of the climate system to test hypotheses about the physical mechanisms that may drive glacial cycles during the late Pleistocene. Results indicate that a permanent doubling of CO₂ generates a 11.1°C rise in Antarctic temperature. Large variations in atmospheric CO₂ over glacial cycles are driven by changes in sea ice and sea surface temperature in southern oceans and marine biological activity. The latter can be represented by a two-step process in which iron dust increases biological activity and the increase in biological activity reduces CO₂ concentrations. Glacial variations in ice volume, as proxied by δ¹⁸O are driven by changes in CO₂ concentrations, global and high latitude solar insolation, latitudinal gradients in solar insolation, and the atmospheric concentration of CO₂. The model is able to quantify the effects of ice volume and temperature on sea level, such that in the long-run, sea level rises 14 m per 0.11‰ δ¹⁸O and about 17 m/°C of sea surface temperature in southern oceans. Beyond these specific results, the multivariate model suggests omitted variables may bias bivariate analyses of these mechanisms.

[1] Here we report 420 kyr long records of sediment geochemical and color variations from the southwestern Iberian Margin. We synchronized the Iberian Margin sediment record to Antarctic ice cores and speleothem records on millennial time scales and investigated the phase responses relative to orbital forcing of multiple proxy records available from these cores. Iberian Margin sediments contain strong precession power. Sediment “redness” (a* and 570–560 nm) and the ratio of long-chain alcohols to n-alkanes (C₂₆OH/(C₂₆OH + C₂₉)) are highly coherent and in-phase with precession. Redder layers and more oxidizing conditions (low alcohol ratio) occur near precession minima (summer insolation maxima). We suggest these proxies respond rapidly to low-latitude insolation forcing by wind-driven processes (e.g., dust transport, upwelling, precipitation). Most Iberian Margin sediment parameters lag obliquity maxima by 7–8 ka, indicating a consistent linear response to insolation forcing at obliquity frequencies driven mainly by high-latitude processes. Although the lengths of the time series are short (420 ka) for detecting 100 kyr eccentricity cycles, the phase relationships support those obtained by Shackleton []. Antarctic temperature and the Iberian Margin alcohol ratios (C₂₆OH/(C₂₆OH + C₂₉)) lead eccentricity maxima by 6 kyr, with lower ratios (increased oxygenation) occurring at eccentricity maxima. CO₂, CH₄, and Iberian SST are nearly in phase with eccentricity, and minimum ice volume (as inferred from Pacific δ¹⁸O_seawater) lags eccentricity maxima by 10 kyr. The phase relationships derived in this study continue to support a potential role of the Earth's carbon cycle in contributing to the 100 kyr cycle.