Marine ammonia oxidizing archaea (AOA) produce isoprenoid glycerol dibiphytanyl glycerol tetraethers (GDGTs) which form the basis of seawater temperature proxy TEX86. Although most studies use TEX86 for sea surface temperature (SST) reconstructions, maximum GDGT production occurs at and below the nitracline. Moreover, sedimentary GDGT-2/GDGT-3 values >5 reflect GDGT contributions of a deeper dwelling (>100 m) clade of AOA, fueling debate on export mechanisms and the water depth of TEX86 proxy sensitivity. We investigate subseasonal variations in GDGT export depth using 4 new and 19 previously published marine sediment trap records and compare results to real-time biogeochemical and physical hindcast/reanalysis model outputs. Due to the complexity of the biological pump and the often short time series of sediment trap records, no globally consistent pattern emerges. However, GDGT-2/GDGT-3 ratios imply seasonal changes in GDGT export depth, and often correlate to changes in the depth (negative) or intensity (positive) of maximum net primary production (NPP). Increased/shallower maximum NPP also correlate positively with GDGT flux at several sites, indicating that NPP exerts a strong control on GDGT origin depth. Mechanistically, increased/shallower maximum NPP incorporates relatively more shallow clade GDGTs into sinking particles, leading to lower GDGT-2/GDGT-3 values. Additionally, GDGT-2/GDGT-3 values correlate with TEX86 in most sediment traps, suggesting that, on sub-annual timescales, mixing of shallow and deep-clade derived GDGTs rather than SST changes causes variations in TEX86. TEX86-based temperatures are up to 0.5 degrees C lower per unit increase in GDGT-2/GDGT-3, but the North Atlantic deviates from this global trend with a positive correlation.

Insight in the spatial evolution of absolute land temperature is crucial for understanding the dynamics of East Asian Summer Monsoon (EASM) precipitation, which governs the water supply for over 20% of the global population. The spatiotemporal evolution of land surface temperatures in East Asia is however not well documented. Here, we use paleothermometry based on membrane lipids of soil bacteria, so-called brGDGTs, to reconstruct growing season temperatures (i.e., temperatures above freezing) for seven sections across the Chinese Loess Plateau (CLP) over the last deglaciation. Our records show that the amplitude of warming over the past similar to 40 thousand years (Kyr) increased with elevation, indicating the sensitivity of high-elevation areas to ongoing warming. Notably, the onset of warming on the lower-elevation, southeastern CLP precedes that in the higher-elevation northwest by up to similar to 23 Kyr. We propose that this spatial offset arises from variations in growing season length across the CLP, where a longer growing season at low elevation allows for a stronger influence of obliquity on integrated insolation, leading to an apparent early onset of warming in the brGDGT-based temperature records. Conversely, on the northwestern CLP, precession dominates insolation variations due to the shorter growing season at higher elevation. Climate model outputs confirms the importance of growing season length on orbital-scale temperature evolution, and thus spatial offsets in reconstructed warming patterns on the CLP.

The response of the climate system to rapid carbon-cycle perturbations can be constrained by studying past transient climate events such as the Paleocene–Eocene Thermal Maximum (PETM, ~56 million years ago). The PETM is marked by a massive input of isotopically light carbon, as recorded by a 3–4‰ negative carbon isotope excursion (CIE) in sedimentary records globally. Estimates of the duration of the rapid onset of the CIE range from a few hundred to several thousand years. The exact duration remains poorly constrained due to the scarcity of marine sedimentary records that 1) have sufficiently high sedimentation rates to resolve rapid decadal- to centennial scale transitions, 2) provide robust controls on sedimentation rates and event timing, and 3) preserve proxy data that record perturbations of the dissolved inorganic carbon (DIC) pool. Consequently, the rate of carbon release during the CIE onset, and its relevance for understanding anthropogenic climate change, remains unclear.International Ocean Discovery Program (IODP) Expedition 396 recovered expanded PETM successions on the Norwegian Margin, including a microlaminated CIE onset interval that preserves decadal-scale variability. We document the first occurrence of haptophyte alkenones from the onset of the PETM CIE and present a high-resolution record of their stable carbon isotopic variability (δ¹³Calk) across the onset interval. The δ¹³Calk records variations in the (isotopic) composition and concentration of the dissolved inorganic carbon (DIC) pool. We show that the δ¹³Calk record is not strongly influenced by local (volcanically induced) input of ¹³C-depleted carbon based on high-resolution sedimentary mercury and polyaromatic hydrocarbon data from this interval. Finally, we provide robust age control from the diatom laminations, enabling a direct and well-constrained estimate of the duration of the global CIE onset interval.

Archaea are single-celled microorganisms that are abundant in marine environments and play a key role in the carbon and nitrogen cycles. Archaea can biosynthesize a wide variety of isoprenoid membrane lipids, including isoprenoid glycerol dibiphytanyl glycerol tetraethers (isoGDGTs). Experimental and empirical evidence demonstrates that the number of cyclopentane moieties in isoGDGTs is related to growth temperature, leading to the formulation and development of the TEX86 ocean temperature proxy. The TEX86 proxy has been widely applied to marine sediments spanning the last 190 million years and has revealed unique insights into the evolution of ocean temperatures over diverse timescales. Other indices have been developed using archaeal lipids to reconstruct ecological and biogeochemical processes that operate within the marine realm. However, several knowledge gaps (e.g., depth of export production, non-temperature controls, application in non-analogue climates) limit the application of archaeal lipid-based proxies in modern and ancient marine environments. In this review, we critically assess the utility of archaeal lipids as tracers for (paleo) environmental change, with an emphasis on the TEX86 paleotemperature proxy.

The strength of the Atlantic Meridional Overturning Circulation (AMOC), in terms of streamfunction, is considered to depend partly on salt supply from the Indian Ocean through Agulhas Leakage (AL). In turn, AL is regulated by the position of the Southern Ocean subtropical front, which creates the pathway of the leaking around the African continent. Here, to evaluate the links between the subtropical front, AL and AMOC, we present latitudinal shifts of the subtropical front, and thereby potential AL changes, using dinoflagellate cysts and biomarkers in sediment cores from the Agulhas Plateau covering the late Pliocene (3,600–2,580 thousand years ago (ka)). We subsequently compare our frontal migration and AL reconstruction with ocean surface and bottom records along the AMOC pathway, and climate model simulations, to evaluate the influence of the AL on the AMOC. We find that the northward migration of the subtropical front gradually reduced the volume and salt supply of AL from 3,600 ka to 3,300 ka, whereas the AMOC intensified. We conclude that the causal link between the AL and AMOC was disconnected during the late Pliocene, challenging the presumed role of the AL in modulating the AMOC. Northward movement of the Southern Ocean subtropical front diminished salt transport by Agulhas Leakage in the late Pliocene, although this had no apparent influence on the strength of the Atlantic Meridional Overturning Circulation, according to proxy records from marine sediment cores.

River systems transport and transform organic carbon (OC) from the terrestrial realm, before delivering this organic matter to deposition centers. Organic carbon with different ages, such as i) modern organic matter, ii) pre-aged organic matter from surface soils or riparian zones or iii) petrogenic or rock-derived organic matter, is transported under different environmental conditions. Using a 30-month high-resolution time series study of the organic matter content of the suspended load in the subalpine Sihl River watershed (Switzerland), the impact of hydrology and seasonality on the amount and source of organic matter was determined.Previous work on the distribution and amount of suspended bulk OM and vegetation derived lipid biomarkers (long chain fatty acids and n-alkanes) revealed that hydrology and seasonality determine their fluxes (i.e. Schwab et al., 2025). Specifically, storms are interpreted to promote the mobilization of both contemporary plant detritus and surface soils. Because plant waxes are sourced from both modern vegetation and pre-aged soils, the unique contribution of pre-aged soil material was not targeted. Now, the analysis of branched GDGTs, bacterial membrane-spanning lipids produced in high abundance in soils, allows to track this specific C pool. Furthermore, these three lipid classes are expected to show a different recalcitrance to degradations (fatty acids>GDGTs>n-alkanes), which allows to determine the effect of age and degradation on the composition of suspended organic matter.Across the sampling period, the export of branched GDGTs closely follows the hydrograph. High discharge conditions (>12.7 m3 s−1), typified by a high suspended sediment load, result in a high brGDGT export flux. The distribution of brGDGTs in these conditions points towards a higher altitude source of brGDGTs during winter, compared with summer. This is distinct from the lower altitude source derived from plant wax distributions (Schwab et al., 2023). Changes in relative contribution of the three biomarker classes indicate the presence of three end-members, i) an end-member of recently produced fresh organic matter, dominated by long-chain fatty acids, ii) an end-member with strongly degraded organic matter (n-alkane Carbon Preference Index < 2), dominated by n-alkanes and iii) a poorly defined end-member with increased n-alkane and GDGT concentrations, interpreted as an input of soils. Remarkably, the content of the radio-active isotope 14C (F14C), is not uniform for given end-member mixtures, indicating that age alone does not determine the relative abundance of the lipid classes.In low discharge conditions, the low contribution of soil-derived GDGTs is overwritten by GDGTs produced in the aquatic system. As GDGT distributions reflect their production environment (soil versus aquatic), the use of GDGT ratios to quantify soil-derived versus aquatic bacterial biomass is evaluated. The direct effect of temperature on GDGTs produced in low discharge conditions, however, results in large ranges of their ratio values, complicating their proposed interpretation as a tracer for the provenance of aquatic biomass in river systems.References:Schwab, M. S., Haghipour, N. & Eglinton, T. I. Geochimica et Cosmochimica Acta 391, 31–48 (2025).

Changes in past East Asian climate and monsoon intensity have been inferred from a wide variety of paleoclimate archives. However, quantitative reconstruction of land surface temperatures in East Asia remains sparse. Here we present a 75-kyr temperature record derived from the carbonate clumped isotope composition (Delta(47)) of land snail shells from a loess-paleosol sequence at Yuanbao, on western edge of the Chinese Loess Plateau (CLP). Modern growing season (mid-April to September) temperature based on Delta(47) (T-47) is 21.2 +/- 1.2 degrees C. The T-47 record reveals that there are certain periods where land surface temperatures were lower: the last glacial maximum (LGM) was similar to 7 degrees C colder, Marine Isotope Stage 3 (MIS3) similar to 5 degrees C and MIS4 similar to 6 degrees C, but also the mid-Holocene was similar to 9 degrees C colder than present day. Temperatures similar to present day occurred during Northern Hemisphere Summer Insolation (NHSI) minima within MIS3 and the B & oslash;lling-Aller & oslash;d (BA). Monsoon precipitation reconstructions based on organic and inorganic geochemical proxies from the same loess-paleosol section indicate that these warm periods are characterized by relatively dry conditions. This is further supported by the relative enrichment in the temperature-independent oxygen isotope composition of snail body water (delta O-18(bw)) during these time intervals, reflecting a negative moisture balance. In contrast, the unexpected low T-47 for the mid-Holocene could be the result of wet conditions. Our record thus suggests that soil moisture availability exerts a strong influence on land surface temperatures recorded by snails stored in loess archives.

The Miocene Climatic Optimum (MCO; 16.9-14.7 Ma) was a relatively warm period with atmospheric CO2 averaging similar to 500 mu atm but CO2 change across its onset is poorly documented. We present a record of algal 13C-fractionation covering the Early to Middle Miocene (similar to 18.5-15 Ma), with a gap at the MCO onset, from Ocean Drilling Program Site 959 in the tropical Atlantic. Bulk marine organic carbon, alkenones and the dinoflagellate cyst species Spiniferites ramosus all show higher 13C-fractionation within the MCO than in the interval below the MCO. Based on various models to convert this signal to CO2, including a new statistical model based on core top and culture data, these records imply a CO2 rise of similar to 100-150 mu atm across the MCO onset, consistent with previously published information.

In the past four decades, high latitude regions have been warming 2 to 4 times more rapidly than the global average, and their ocean and cryosphere are rapidly changing. Arctic sea-ice loss, complex Antarctic sea-ice variability, instability of the Greenland and Antarctica continental icesheets, and melting have consequence for the entire planet including sea-level rise, changing ocean currents, and impacts on polar species, ecosystems and biodiversity. The International Ocean Discovery Program (IODP) completed 8 expeditions in high latitude locations during the past ~10 years. One aim that these expeditions share is to study ocean and cryosphere responses to warm climates in the geological past to get insights into cryosphere instability thresholds in a (future) warm climate scenario. Obtaining continuous high latitude records is challenging, but even snapshot views of the past offer important insights into the interaction among climate, ocean and cryosphere (in)stability, and ecosystem responses.On behalf of numerous collaborators, I will present an overview of what we have learned so far about ocean and cryosphere variability during warm periods of the Neogene (Miocene Climatic Optimum and Pliocene) and the Quaternary. I will discuss (preliminary) results, mostly centered on palynology, obtained from Expeditions 374 (Ross Sea) and 400 (NW Greenland) in the context of additional sedimentological and geochemical data, and link them to results from previous (I)ODP expeditions and on-going projects.

The Amery Ice Shelf, the third largest ice shelf at the head of Prydz Bay, and one of the four regions where Antarctic Deep Waters form, is reported as one of the most stable portions of the East Antarctic Ice Sheet (EAIS). Yet, its response to future warming remains uncertain. The Miocene Climatic Optimum (MCO, ~17–15 million years ago) is the warmest period of the past 23 million years, with global temperatures 3–8°C above modern and pCO2 of 400–600 ppm, similar to end-century projections. It therefore provides a valuable opportunity to investigate EAIS stability under warm conditions. Here, we present a combined lipid biomarker, palynology and XRF record from ODP Site 1165, offshore Prydz Bay, spanning ~16.3-16 Ma at an unprecedented millennial-scale resolution, crucial for understanding the near-future EAIS conditions in a warmer world. Interestingly, the record shows recurrent pulse-like intense organic matter oxidation events associated with elevated proportions of reworked and oxidation-resistant in situ dinoflagellate cysts as well as ice-rafted debris (IRD). IRD presence in this record was previously interpreted as evidence for deglaciation. However, deglaciation, meltwater and subsequent stratification are somewhat in contrast with seafloor oxidation. Oxidation events at the seafloor may rather be linked to oxygen-rich deepwater associated with EAIS and sea ice dynamics at location, or other processes we are investigating. Excluding the interval where organic matter oxidation is recorded, the remaining record indicates relatively stable seawater conditions. Specifically regarding sea water temperature (SST) based on glycerol dialkyl glycerol tetraethers (GDGTs)-based SST proxy (TEX86) and alkenone-based SST proxy both suggest SSTs around 9-16°C, although hydroxylated-GDGTs suggest much lower SSTs around 4-9°C. Furthermore, the occurrence of plant-derived fatty acids and pollen-spore assemblages indicate a sustained woody-tundra vegetation and an intensified hydrological cycle on the hinterland than modern throughout the record.

Dust deposition in the ocean can enhance carbon export through fertilization and ballasting. However, the processes that subsequently drive the transfer of dust particles through the water column to the ocean floor remain unresolved. To assess the occurrence of vertical dust export and potential facilitating conditions we present dust fluxes and grain-size distributions collected by sediment traps in Bannock Basin, Mediterranean Sea, complemented with three years of particulate organic (POC) and inorganic (PIC) carbon fluxes. Sediment traps were deployed at three water depths (∼550–800 m, ∼1750–2000 m, and ∼ 3000 m) for nine years between 1999 and 2011 with 10–23 days sampling intervals.Maximum dust and total mass flux (TMF) usually occurred in spring and summer, concomitant with the season of largest atmospheric dust transport indicated by remote sensing observations. Peaks in dust fluxes occur synchronously in the three sediment traps, indicating high sinking velocities during dust events. However, not all dust events in the upper trap are transferred to the deeper traps, and average modal grain sizes are larger in the deeper traps. Furthermore, Stokesian settling velocities, corresponding to particle sizes of the dust, are too low to account for these high sinking velocities. This, combined with concomitant peaks of dust, POC, and TMF, suggests that deposited dust is mainly exported as dust-ballasted aggregates during spring and summer. However, a shift in the timing of dust flux maxima from summer to winter in 2009 suggests that the processes driving dust export may vary interannually, and emphasizes the importance of longer time series.

Methane pockmarks and shallow gas systems are prominent geomorphological features in the Baltic Sea that act as hotspots of microbial activity. In the Gda & nacute;sk Basin, pockmarks vary in gas-seepage intensity and in the extent of freshened porewater discharge, both of which influence the archaeal community structure and the composition of internal methane biofilters. The objective of this study was to examine the effects of methane seepage and freshened porewater on the composition of archaeal communities and on the isoprenoid glycerol dialkyl glycerol tetraethers (iGDGTs), membrane lipids synthesised by these communities, across the gas systems examined. Additionally, the effects of these environmental factors on the use and interpretation of iGDGT-based proxies under conditions of gas and water seepage were assessed. The study investigates whether iGDGT patterns in these Baltic gas systems reflect methane-driven processes, including anaerobic oxidation of methane (AOM) and methanogenesis, porewater freshening, or pelagic contributions from ammonia-oxidising archaea (AOA). The results show elevated iGDGT concentrations in pockmark cores compared with reference non-pockmark cores; however, the summed iGDGT concentration varies by site. Overall, iGDGT concentrations are much higher at sites with reduced seabed pockmark activity and weak porewater freshening. Nevertheless, consistently low Methane Index values (MI < 0.09), together with low GDGT-0 / crenarchaeol (< 1) and low GDGT-2 / cren (< 0.04) ratios, indicate that the iGDGT pool lacks the typical enrichment in GDGT-1 to -3 associated with AOM, suggesting no AOM imprint on the iGDGT pool. However, 16S rRNA analysis revealed that the anaerobic methanotrophic archaeal lineages (ANME) consist of ANME-2b and ANME-3. A strong positive correlation between OH-GDGTs and crenarchaeol, together with the consistency of OH-GDGT% values with those previously reported for Baltic Sea surface sediments, suggests a thaumarchaeal source of iGDGTs in the studied pockmark and reference cores. The Branched and Isoprenoid Tetraether (BIT) index values suggest marine archaeal GDGT production. In this system, iGDGT-based proxies primarily reflect a strong pelagic presence of AOA, as indicated by the dominance of crenarchaeol. This suggests that, despite the local presence of methanogenic and ANME-related archaeal groups, methane-related AOM does not influence the iGDGT signal due to the archaeal community structure. These findings highlight the complex interplay between freshened porewater and gas seepage in shaping archaeal communities, and the role of ammonia-oxidising Nitrososphaeria in controlling iGDGT composition and the sedimentary record.

Currently available reconstructions of past East Asian monsoon (EAM) variability achieve annual resolution at best, which limits their ability to resolve seasonal variations in precipitation and temperature. To address this gap, we present sub-annual scale reconstructions of temperature and precipitation variability based on carbonate clumped isotope (Delta(47)) and stable oxygen isotope (delta O-18(shell)) measurements from modern and fossil land snail shells collected from the western (Yuanbao, YB) and southeastern (Lingbao, LB) edge of the Chinese Loess Plateau (CLP). Whole-shell Delta(47)-derived temperatures (T-47) from different modern snail species are consistent with land surface temperatures measured during their growing season (mid-April to September at YB and mid-March to October at LB), and show minimal inter-species differences, highlighting the ecological robustness of snail-based T-47 reconstructions. Our intra-shell Delta(47)-delta O-18-delta C-13 data show no obvious evidence of disequilibrium fractionation, supporting that land snail shell aragonite forms near isotopic equilibrium in natural settings. Notably, the reconstructed intra-shell T-47 profiles show a sub-annual temperature variability of 7-10 degrees C and potential signs of short-term thermal stress. Reconstructed body water delta O-18 (delta O-18(bw)) values from whole-shells are significantly enriched (by similar to 3-6.5 parts per thousand, p < 0.05) compared to local precipitation delta O-18 (delta O-18(p)), due to evaporative effects and micro-environmental conditions. Intra-shell delta O-18(bw) profiles reveal sub-annual fluctuations that follow seasonal delta O-18(p) patterns, capturing dry-season evaporative isotopic enrichment and wet-season depletion masked in whole-shell averages. The T-47 from early Holocene and last glacial maximum (LGM)-aged shells provides geochemical evidence of a cooler growing season than today, perhaps caused by extended growing seasons during the early Holocene and climatically restricted ones during the LGM. Lower and more stable intra-shell T-47 and more negative delta O-18(bw) values during the wet seasons highlight seasonal hydroclimatic shifts under glacial boundary conditions. Together, our results demonstrate the sensitivity of snail shell geochemistry to hydroclimatic seasonality and support the use of combined intra-shell delta O-18 and Delta(47) analyses to resolve climate seasonality beyond the resolution of traditional proxies.

Our current understanding of past changes in East Asian monsoon climate variability is largely based on loess-paleosol sequences and speleothem δ18O records. Although most records have provided insight on the strength of summer monsoon precipitation, past temperature variations over East Asia are so far relatively poorly understood. Here we quantitatively reconstruct a high-resolution land temperature for central China covering the past 250 kyr, based on soil bacterial lipid signatures, co-called branched glycerol dialkyl glycerol tetraethers (brGDGTs) preserved in a loess-paleosol sequence at Mangshan on the eastern Chinese Loess Plateau (CLP). We find that the brGDGT-based temperature is dominated by precession cycles (21 kyr), except during the last deglaciation when temperature change was mainly driven by obliquity due to low eccentricity, consistent with model outputs. Notably, our record provides first evidence of extreme cooling events during glacial times when summer insolation decreases to a critical value as predicted by model simulations. Furthermore, the degree of cyclization (DC) of brGDGTs, which is suggested to indicate moisture availability, also shows clear precession cycles but does not show extreme events in response to the critical low insolation values. Our results thus indicate that the warm season temperature and moisture are mainly forced by precession, and extreme cooling events could be triggered by low summer insolation during glacial times.

Changes in past East Asian monsoon (EAM) climate have been inferred from records of speleothem δ18O and the magnetic susceptibility (MagSus) of loess sequences on the Chinese Loess Plateau (CLP). However, where the speleothem record is dominated by a 23-kyr cycle, loess MagSus primarily shows a 100-kyr cycle. Generating a long-term high-resolution record of plant wax hydrogen isotopes (δ2Hwax) from the Yuanbao section on the western CLP reveals that variations in δ2Hwax follow the precessional pattern of the speleothem record, as opposed to the glacial-interglacial changes in MagSus from the same loess section. We, therefore, propose that plant waxes mainly record the δ2H of precipitation during the growing season, whereas MagSus represents an annual climate signal, including precipitation and temperature. This implies that summer vs annual climate variability is driven by distinct orbital forcings.Regardless, these proxies only allow for qualitative reconstructions of past EAM climate; a method to generate records of absolute monsoon precipitation changes and also leads to consistent results across the CLP is still lacking. We find that in the Yuanbao section, the degree of cyclisation (DC) of branched tetraether membrane lipids, so-called brGDGTs, which are membrane lipids of soil bacteria that are mostly known for their temperature-sensitivity, closely tracks the changes in δ2Hwax. The positive relationship of the DC with mean annual precipitation (MAP) in surface soils from the CLP enables us to quantify past MAP at Yuanbao, but also at other sites on the CLP with existing brGDGT datasets. This reveals a spatial gradient in MAP that is most pronounced during glacials, when the western CLP experiences relatively more arid conditions. Furthermore, the DC records provide independent support for precession as main forcing of precipitation on the CLP, as opposed to the 100-kyr cycle recorded by MagSus, which rather reflects the relative intensity of the EAM.

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are a suite of membrane lipids that are widely used as empirical proxies for past temperature and pH. Although the stereochemistry of their glycerol moiety suggests that they are produced by bacteria, the exact producers and the biosynthetic pathway of brGDGTs remain unclear. Here we report the occurrence of tetraester and mixed ester/ether membrane-spanning lipids with a backbone consisting of iso-diabolic acid (iso-DA) containing up to two additional methyl groups in mineral soils from Nepal and Rwanda. These compounds are presumed intermediate products during brGDGT synthesis but had not been detected in cultures or the environment before. Interestingly, while acid hydrolysis of the polar fraction releases iso-DA in the soil from Nepal, monoalkyl glycerol ethers with iso-C15 and iso-C17 chains are released in the soil from Rwanda. These results support both current hypotheses that brGDGT synthesis can occur via tail-to-tail condensation of two iso-C15 fatty acids to form iso-DA, as well as through the reduction of diesters to diethers and subsequent carbon-carbon linking as shown to occur during the synthesis of archaeal GDGTs.

Estimates of sea surface temperature (SST) in the geologic past often rely on geochemical proxies, including alkenone unsaturation ratios (UK’37), the proportion of cyclopentane rings in glycerol dibiphytanyl glycerol tetraethers (GDGTs; TEX86), δ18O and Mg/Ca in planktonic foraminifera, and clumped isotopes in biogenic carbonates (Δ47). Global calibrations show robust agreements between proxies and the temperature of the environment. However, proxy values in the eastern Mediterranean Sea are often offset from expected values based on these global relationships.Here we aim to explain the Meditrerranean Sea proxy bias using sediment traps moored in the water column at 500, 1500, and 2500 m depth in the Ionian Sea between 1999 and 2018. We compare proxy values in trap material to those in surface sediment from the same site. UK’37-based SSTs (~12-22 °C) and TEX86-based SSTs (~28-30 °C) vary seasonally, although they differ from satellite-based SSTs (~16-27 °C). No significant variations in mean Mg/Ca or δ18O values in G. ruber or in coccolith Δ47 values were observed, indicating that these proxies do not vary on seasonal timescales in sinking particles at this site. Ultimately, however, sediments should record a flux-averaged proxy value. To this end, we explore export patterns of biomarkers and foraminifera.We find that export of alkenones, GDGTs, and foraminifera exhibit different seasonality. Specifically, alkenone export typically peaks twice per year in late winter and late summer, maximum GDGT export often occurs in late winter, and export of planktonic foraminifera generally peaks in summer. Furthermore, alkenone export exhibits very little inter-annual variability, whereas the timing of GDGT export is more variable, and the peak flux of foraminifera is highly variable between years.Flux-weighted UK’37- and TEX86-, and mean coccolith Δ47-based SSTs of 15, 29, and 15 ± 2 °C, respectively are offset from mean annual average satellite-based SSTs of 21 °C, whereas Mg/Ca and δ18O of G. ruber both yield average temperatures that are similar to the satellite-derived SSTs. Notably, whereas most proxy values measured in the surface sediment closely reflect those in the sediment trap material, the UK’37-based SST (13 °C) differs from the flux-weighted average in the sediment trap.These results will be discussed in the context of seasonality, nutrient availability, dwelling depth, ecology, and physiological processes which may influence proxy values measured in the sediment trap and in underlying sediments.