Deglacial Subantarctic CO2 outgassing driven by a weakened solubility pump

Dai, Yuhao; Yu, Jimin; Ren, Haojia; Ji, Xuan

doi:10.1038/s41467-022-32895-9

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Published: 03 September 2022

Deglacial Subantarctic CO₂ outgassing driven by a weakened solubility pump

Nature Communications volume 13, Article number: 5193 (2022) Cite this article

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Abstract

The Subantarctic Southern Ocean has long been thought to be an important contributor to increases in atmospheric carbon dioxide partial pressure (pCO₂) during glacial-interglacial transitions. Extensive studies suggest that a weakened biological pump, a process associated with nutrient utilization efficiency, drove up surface-water pCO₂ in this region during deglaciations. By contrast, regional influences of the solubility pump, a process mainly linked to temperature variations, have been largely overlooked. Here, we evaluate relative roles of the biological and solubility pumps in determining surface-water pCO₂ variabilities in the Subantarctic Southern Ocean during the last deglaciation, based on paired reconstructions of surface-water pCO₂, temperature, and nutrient utilization efficiency. We show that compared to the biological pump, the solubility pump imposed a strong impact on deglacial Subantarctic surface-water pCO₂ variabilities. Our findings therefore reveal a previously underappreciated role of the solubility pump in modulating deglacial Subantarctic CO₂ release and possibly past atmospheric pCO₂ fluctuations.

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Introduction

The Southern Ocean is widely regarded as a crucial source of carbon dioxide (CO₂) to the atmosphere during glacial terminations because this region serves as a window for CO₂ exchanges between the atmosphere and the ocean interior^1,2,3,4. In the Southern Ocean, prevailing southern hemisphere westerly winds drive upwelling of carbon-rich deep waters surrounding Antarctica, some of which are transported northward to the Subantarctic Zone (SAZ)^5,6. The surface SAZ exposes the newly upwelled carbon-rich deep waters to the atmosphere enabling CO₂ outgassing, before these waters are entrained to form intermediate and mode waters^5,6,7.

Changes in the SAZ have been thought to be critical to deglacial atmospheric pCO₂ rises, with a contribution estimated to be around 40 ppm^8,9,10,11. In the SAZ, CO₂ tends to escape to the atmosphere due to elevated surface-water CO₂ partial pressures (pCO₂) driven by high surface-water dissolved inorganic carbon (DIC) concentrations^12,13 associated with the newly upwelled deep waters surrounding Antarctica. CO₂ outgassing in the SAZ is somewhat alleviated by biologically driven carbon sequestration that exports carbon to depths in the form of organic matter, a process called the biological pump^1,14,15. In addition to this biological process, it is important to note that surface-water pCO₂ is further affected by CO₂ solubility determined by seawater temperature and salinity, a process known as the solubility pump^14,16. Changes in the solubility pump have been shown by modeling studies to contribute substantially to atmospheric pCO₂ variability^2,17,18,19. Everything else being equal, warming lowers CO₂ solubility in seawater and thus increases surface-water pCO₂ with an effect to cause CO₂ outgassing from the ocean to the atmosphere¹⁶. Surface-water pCO₂ increases with increasing salinity, but the salinity effect on the CO₂ solubility is generally smaller than the temperature effect in most regions²⁰ (Supplementary Fig. 2).

During glacial terminations, it has been proposed that the biological pump efficiency was lowered, driving up CO₂ outgassing in the SAZ^{1,11,21,22,23}. The deglacial SAZ biological pump efficiency decline has been linked to reduced supplies of micronutrients such as iron via eolian lithogenic fluxes^10,11,24. In this case, weakened biological pump would leave more carbon unused in the SAZ surface, raising surface-water pCO₂ which would stimulate CO₂ outgassing¹. On the other hand, as manifested by Southern Ocean temperature reconstructions^25,26,27, deglacial SAZ warming, in theory, should weaken the solubility pump, raise surface-water pCO₂, and promote CO₂ outgassing¹⁶ (Supplementary Fig. 1). Existing reconstructions in the SAZ indeed show elevated surface-water pCO₂ during the last deglaciation (~18-11 ka BP)^22,23. Yet, it remains unknown regarding the respective roles of biological and solubility pump changes in affecting these past surface-water pCO₂ rises in the SAZ and by extension atmospheric pCO₂ changes.

Here, we systematically investigate the contributions of the biological and solubility pumps to the SAZ surface-water pCO₂ changes in the modern ocean and during the last deglaciation. For the deglacial investigation, we have generated a surface-water pCO₂ record using a sediment core from the Southwest Pacific, paired with nutrient utilization efficiency and sea surface temperature (SST) reconstructions. We evaluate the relative roles of biological and solubility pumps in regulating deglacial surface-water pCO₂ changes at our site location. The same approach is further applied to published records at three additional SAZ locations. Moreover, we examine simulated early deglacial carbon cycle changes in an earth system model²⁸ to distinguish effects of the two pumps during the early deglaciation. All our investigations suggest a strong solubility pump effect on the SAZ surface-water pCO₂ changes, urging a rethinking of mechanisms underlying deglacial CO₂ outgassing from the SAZ and, by extension, past atmospheric pCO₂ variabilities.

Results

Solubility pump in the modern SAZ

In the modern SAZ, both biological and solubility pumps strongly control spatial distribution and seasonal variability of surface-water pCO₂^12,13,29. Regarding the spatial distribution, Fig. 1a shows small northward declines in annual mean surface-water pCO₂ within the SAZ, where nutrient (nitrate) is progressively utilized equatorward (Fig. 1b). Enhanced nutrient consumption would lower surface-water pCO₂, but this biological effect is compensated by the opposing influence of equatorward surface-water warming in the SAZ (Fig. 1c). Consequently, surface-water pCO₂ changes caused by nutrient consumption is largely balanced by decreasing CO₂ solubility, and the total northward surface-water pCO₂ decline is marginal. Regarding the seasonal variability, Fig. 1d shows minimal monthly surface-water pCO₂ deviation from the annual mean levels in the SAZ. By contrast, seasonal changes in the biological and solubility pumps each cause surface-water pCO₂ to fluctuate ~40 ppm around the annual mean level (Fig. 1e, f)^12,29. Because the strong (weak) biological pump occurs during warm (cold) seasons with low (high) CO₂ solubility, effects from the biological and solubility pumps generally cancel each other, leading to little seasonal surface-water pCO₂ variability. Combined, these spatial and temporal patterns suggest that the solubility pump plays a critical role, comparable to that of the biological pump, in determining the SAZ surface-water pCO₂ fluctuations in the modern ocean. Next, we move on to explore the impact of the solubility pump on past surface-water pCO₂ changes, a topic that has rarely been studied by proxy reconstructions.

**Fig. 1: Surface-water chemistry in the modern Southern Ocean.**

New deglacial SAZ surface-water pCO₂ and δ¹⁵N records

We present records of surface-water pCO₂ and nutrient utilization, respectively, based on boron isotopes (δ¹¹B)^22,30,31 and foraminifera-bound nitrogen isotopes (δ¹⁵N_FB) of mixed-layer-dwelling planktic foraminifera species Globigerina bulloides for site MD97-2106 from the Southwest Pacific Ocean (Fig. 1). Site MD97-2106 (45.15°S, 146.28°E) is located in the northern part of the SAZ. Compared to today, the Subtropical Front, the northern boundary of the SAZ, possibly shifted northward to Tasmania during the Last Glacial Maximum (LGM; ~22-18 ka)^32,33. During the last deglaciation, the Subtropical Front might migrate southwards^32,33, but unlikely to the south of our site. This is because the Subtropical Front marks a ~4 °C SST gradient³⁴, while reconstructions at our site only show ~3 °C SST change during the entire deglaciation^35,36. Consequently, our site was likely located within the SAZ during the entire last deglaciation, ideal for investigating deglacial SAZ surface conditions. The age model of site MD97-2106 during the last deglaciation is based on new radiocarbon dates and tuning of SST at this site to Antarctic temperatures²⁶ (Fig. 2a, b; Supplementary Table 1, Supplementary Fig. 4). See Methods for analytical details.

**Fig. 2: Surface-water reconstructions at site MD97-2106.**

Our reconstructed surface-water pCO₂ at site MD97-2106 fluctuated between ~210 and ~270 ppm during the last deglaciation, reached ~270 ppm at the onset of the Holocene, and increased by ~20 ppm from the early to middle Holocene (Fig. 2d). The range of deglacial surface-water pCO₂ at site MD97-2106 is comparable to previous reconstructions^22,23. At our site, surface-water pCO₂ briefly dropped below the atmospheric pCO₂ values during the Antarctic Cold Reversal (ACR; 14.6–12.8 ka BP) and the Younger Dryas (YD; 12.8–11.7 ka BP) (Fig. 2d).

In addition to our surface-water pCO₂ reconstructions, we employ δ¹⁵N_FB to infer nitrate utilization efficiency at site MD97-2106. δ¹⁵N_FB reflects δ¹⁵N of surface-water nitrate taken up by foraminifera which increases as surface nitrate is progressively consumed by photosynthetic algae^11,37,38. During Heinrich Stadial 1 (HS1; 18.0-14.6 ka BP) when the age model of our core is well constrained by a warming phase, δ¹⁵N_FB at our site remained roughly unchanged (Fig. 2b, g). This observation is consistent with a precisely dated coral-bound δ¹⁵N record from the same region showing minimal δ¹⁵N variability over the same period²¹ (Supplementary Fig. 9). Maxima of δ¹⁵N_FB occurred during the ACR and the YD, coinciding with surface-water pCO₂ minima. During the Holocene, δ¹⁵N_FB declined by about 2.0‰, consistent with other fossil-bound δ¹⁵N records from the Southern Ocean^{11,21,39,40,41}.

Evaluating past biological and solubility effects at site MD97-2106

We partition surface-water pCO₂ changes at site MD97-2106 into two components caused by changes in biological and solubility pumps, using a similar method previously applied to investigate modern surface-water pCO₂ variability^12,16,29. Firstly, we calculate total in-situ surface-water pCO₂ changes (noted as δpCO₂^TOTAL) relative to the reference age of 18 ka; choosing a different reference age has little effect on our conclusions (Supplementary Fig. 6). Secondly, surface-water pCO₂ is recalculated using carbonate chemistry (i.e., DIC and alkalinity) fixed at the reference age, but using varying SST and sea surface salinity (SSS) based on our reconstructions (Methods). Thirdly, this recalculated surface-water pCO₂ is used to compute changes relative to 18 ka (the reference age). The relative surface-water pCO₂ changes calculated in this way are only driven by SST and SSS, and thus are attributed to the solubility pump effect (noted as δpCO₂^SOL). Fourthly, we calculate the difference between δpCO₂^TOTAL and δpCO₂^SOL, which is defined as the biology-driven surface-water pCO₂ change (noted as δpCO₂^BIO). We also provide an alternative approach to directly calculate δpCO₂^BIO, which yields consistent results with those presented in the main text (Methods; Supplementary Fig. 8). Any influence of external processes on surface-water pCO₂, such as changes associated with frontal shift, is embedded in our method, because these external processes affect surface-water pCO₂ via the carbonate chemistry, SST-SSS, or both. See “Methods” for calculation details.

As can be seen from Fig. 2f, δpCO₂^BIO at site MD97-2106 fluctuated between ~−20 ppm and ~+40 ppm from the LGM to the early Holocene, followed by a ~20-ppm increase during the Holocene. From 18 to 15 ka, δpCO₂^BIO showed little net change, suggesting marginal influence of biological processes on surface-water pCO₂ variations at our site. During the ACR and the YD, δpCO₂^BIO exhibits mostly negative values, indicating a strengthened biological pump that would lower surface-water pCO₂ during these times. The evolution of δpCO₂^BIO at our site is well corroborated by our δ¹⁵N_FB record from the same core. Little net δpCO₂^BIO change concurred with stable δ¹⁵N_FB during HS1, while negative δpCO₂^BIO during the ACR and the YD coincided with higher δ¹⁵N_FB values which indicate more complete nutrient utilization (Fig. 2f–g). We note that, in addition to nitrate utilization in the SAZ, our δ¹⁵N_FB might have also been affected by δ¹⁵N of nitrate supplied to our site, which depends on the nitrate utilization of the nitrate source^11,21,41,42. Despite these complications, similar deglacial structures in δ¹⁵N_FB and independently derived δpCO₂^BIO suggest that δ¹⁵N_FB at site MD97-2106 reflects local nitrate utilization efficiency. Moreover, given their independent methods, consistent patterns of our δpCO₂^BIO and δ¹⁵N_FB lend strong support to our inference about past biological pump changes at this site. In stark contrast to previous findings in the SAZ^22,23,24, our δpCO₂^BIO and δ¹⁵N_FB suggest that the biological pump played a minor role in contributing to surface-water pCO₂ and thus air-sea CO₂ exchange at site MD97-2106 during HS1 and the YD when atmospheric pCO₂ rose substantially^43,44.

Compared with δpCO₂^BIO, our calculated δpCO₂^SOL, which reflects solubility pump effects, shows a different history (Fig. 2f). As expected, deglacial δpCO₂^SOL increased in response to warming, although this warming effect was slightly counteracted by a declining SSS (Supplementary Fig. 5). From 18 to 10 ka, δpCO₂^SOL showed a net increase of ~20 ppm, contributing to about one-third of the δpCO₂^TOTAL at site MD97-2106 over the same period. More specifically, the δpCO₂^SOL increase dominated the δpCO₂^TOTAL rise from 18 to 15 ka, in contrast to little net change in the concurrent δpCO₂^BIO. This highlights the critical role of the weakened solubility pump in maintaining positive sea-air pCO₂ gradients, which would contribute to the atmospheric pCO₂ rise during HS1. During the YD, rising δpCO₂^SOL helped reverse biological effects (shown by δpCO₂^BIO and δ¹⁵N_FB) to limit the development of negative sea-air pCO₂ gradient (Fig. 2f-g), contributing to the contemporary atmospheric pCO₂ rise.

By separating influences of the biological and solubility pumps downcore, we demonstrate that a substantial portion of deglacial surface-water pCO₂ rise at our site originated from variations in the solubility pump. This suggests that the solubility pump, which has been neglected in previous investigations in the region, played an important role in regulating deglacial surface-water pCO₂ changes in the Pacific SAZ.

Proxy and model data evaluation for broader SAZ

To quantify past influences of biological and solubility pumps in broader SAZ regions, we reanalyze deglacial surface-water pCO₂ changes at three additional locations using published proxy records^22,23 (Figs. 1a; 3b–d). At all the investigated sites, our calculated δpCO₂^BIO suggests little-to-modest biological pump effects on SAZ surface-water pCO₂ during times with large atmospheric pCO₂ rises. For instance, except for a brief excursion at ~17 ka, δpCO₂^BIO at Site ODP 1090 (Fig. 3b) varied little and suggests minimal biological pump effects on surface-water pCO₂ during the last deglaciation²³. At site PS2498-1, despite an overall larger δpCO₂^BIO contribution to surface-water pCO₂ compared to other sites, roughly stable average δpCO₂^BIO during ~14-11 ka contributed little to the observed surface-water pCO₂ rise (Fig. 3c). At site TAN1106-28, δpCO₂^BIO showed a prominent peak at ~16 ka, but the general deglacial trend of δpCO₂^BIO is poorly defined by the low temporal resolution. In contrast to δpCO₂^BIO changes, our calculated δpCO₂^SOL at all studied sites supports that solubility pump changes consistently contributed to deglacial δpCO₂^TOTAL. From 18 to 10 ka, we observe well-defined δpCO₂^SOL increases of ~20 ppm at Site ODP 1090 from the South Atlantic. At site TAN1106-28 from the South Pacific, δpCO₂^SOL increased by ~50 ppm, in response to the deglacial SST change of ~7 °C in part caused by a possible frontal shift over this site²³. Although the record at site PS2498-1 does not cover the entire last deglaciation, δpCO₂^SOL at this site shows a ~30-ppm increase during ~14–11 ka (Fig. 3c). These δpCO₂^SOL changes significantly contribute to, or even dominate, the surface-water pCO₂ variations at these sites, strengthening our findings at site MD97-2106. Overall, our analyses of proxy data from different sectors of the Southern Ocean demonstrate that deglacial surface-water pCO₂ changes in the SAZ are substantially affected by solubility pump changes, rather than solely by biological pump changes as previously assumed^11,22,23.

**Fig. 3: Deglacial surface-water pCO₂, solubility and biological pump effects, dust and opal fluxes, and nutrient utilization at four Subantarctic Zone sites.**

We further scrutinize the role of the solubility pump in affecting deglacial SAZ surface-water pCO₂ in a simulation by climate model LOVECLIM²⁸. In this simulation, a 30-ppm atmospheric pCO₂ increase is achieved during HS1 when the Southern Ocean overturning circulation and southern hemisphere westerly winds are intensified. The rising surface-water pCO₂ in the Southern Ocean is diagnosed as a main CO₂ source for the early deglacial atmospheric pCO₂ increase²⁸. Using the same method applied to proxy data, we quantify δpCO₂^BIO and δpCO₂^SOL changes between 19 ka and 15 ka in this simulation (“Methods”). Our decomposition (Fig. 4) reveals that δpCO₂^BIO changes are either small or tend to lower pCO₂^TOTAL in the SAZ. Because nutrient utilization forced by iron availability is not prescribed in the model, our calculated δpCO₂^BIO per se cannot be used to dismiss iron fertilization effect on deglacial SAZ surface-water pCO₂ changes. By contrast, δpCO₂^SOL changed substantially due to strong surface warming, dominating surface-water δpCO₂^TOTAL rise in the SAZ (Fig. 4). Therefore, our model data analyses suggest that solubility pump changes are crucial for deglacial surface-water pCO₂ and air-sea CO₂ exchange in the SAZ, strengthening our findings based on above extensive proxy reconstructions.

**Fig. 4: Southern Ocean surface-water pCO₂ changes in a climate model simulation during the last deglaciation²⁸.**

Discussion

It is widely thought that declined biological pump efficiency, possibly owing to reducing nutrient utilization associated with dust-borne iron deposition, enhanced CO₂ outgassing in the SAZ and hence atmospheric pCO₂ rises during deglaciations^1,10,11,24. During HS1 when atmospheric pCO₂ raised substantially and dust deposition in Antarctica declined dramatically⁴⁵ (Fig. 3), δpCO₂^BIO, together with independently measured δ¹⁵N_FB, indicates little net biological pump change at site MD97-2106. Over the same period, δpCO₂^BIO shows little increase in response to the reduced iron fertilization inferred from dust deposition in Antarctica⁴⁵ and other examined sites. At two of the examined sites (ODP 1090 and PS2498-1), where opal and lithogenic fluxes are available^24,46,47,48, δpCO₂^BIO shows correlation with neither flux during HS1^24,46,47 (Fig. 3b, c). In addition to local nutrient utilization efficiency, δpCO₂^BIO and δ¹⁵N_FB at a certain site in the SAZ may also be affected by nutrient supplies modulated by shifts of the Southern Ocean fronts^{11,21,39,41,42}. Everything else being equal, poleward movements of the Subtropical and Subantarctic fronts and thus the SAZ during HS1 would reduce nutrient supply, with an effect to raise observed nutrient utilization efficiency, at any given location in the SAZ. During HS1, declining local nutrient utilization efficiency deduced from reduced iron fertilization and poleward front shifts would have opposing effects on SAZ δpCO₂^BIO, and their combined effects may result in minimal δpCO₂^BIO changes overall. Thus, despite the lack of any δpCO₂^BIO decline, our reconstructions imply a potential role of iron fertilization in affecting surface-water pCO₂ through nutrient utilization in the SAZ during HS1.

Instead of a dominant biological contribution, our systematic investigations reveal persistent influences of the solubility pump on surface-water pCO₂ fluctuations in the SAZ under both modern and past conditions. Modern hydrographical data shows that the solubility pump causes surface-water pCO₂ to fluctuate by ~40 ppm seasonally (Fig. 1). New and published proxy data demonstrates a solubility effect that can modulate surface-water pCO₂ by ~20–50 ppm on millennial timescales during the last deglaciation (Figs. 2 and 3). The strong solubility pump influence is likely widespread in the SAZ, as shown by >20 ppm surface-water pCO₂ increase attributable to solubility pump changes during the early deglaciation in a model simulation²⁸ (Fig. 4). Notably, in this model simulation, solubility pump changes in the SAZ lead to strong CO₂ outgassing and, together with other Southern Ocean processes, contribute to a full-scale atmospheric pCO₂ increase during HS1 without invoking nutrient utilization efficiency changes related to iron fertilization²⁸. Based on our analyses on modern data, proxy reconstructions, and modeling outputs, we suggest that a weakened solubility pump, driven by warming, contributed critically to the rising surface-water pCO₂ in the SAZ and thereby maintaining this region as a CO₂ source to the atmosphere during the last deglaciation.

In sum, while our δpCO₂^BIO reconstructions, at face value, indicate little biological pump contributions to deglacial SAZ surface-water pCO₂ variations at various SAZ sites locally, these reconstructions imply iron-related nutrient utilization effects on the deglacial SAZ surface-water pCO₂ variabilities when the influence of frontal shift is considered. Nevertheless, such an iron-related biological effect appears to be smaller than previously thought. Therefore, the common view that the iron-regulated SAZ biological pump changes substantially contributed to the deglacial atmospheric pCO₂ rise^8,9,10,11 may need to be re-evaluated. In comparison to the widely recognized biological pump effect, the potential effect of the solubility pump in the SAZ has been previously overlooked when explaining the past atmospheric pCO₂ changes. Our work demonstrates that the solubility pump plays an indispensable role in modulating SAZ surface-water pCO₂ under both modern and past conditions. We suggest future works on quantifying the effect of SAZ solubility pump on past and possibly future atmospheric pCO₂ changes, which would have important implications for our mechanistic understanding of the global carbon cycle.

Methods

Trace element and boron isotope analyses

About 30 to 40 shells of planktic foraminifera G. bulloides from the 300–355 µm size fraction and >5 mg of G. bulloides shells from the 250–355 µm size fraction were picked for trace element and δ¹¹B analyses, respectively. These samples were cleaned following the “Mg-cleaning” procedure^50,51,52,53. Measurements of B/Ca and Mg/Ca, along with Al/Ca and Mn/Ca for monitoring contaminants, were performed on an iCAP Inductively coupled plasma-mass spectrometry (ICP-MS) at the Australian National University (ANU), following an established method⁵¹.

Separation of boron from sample matrices and measurement of δ¹¹B on a multi-collector-ICP-MS (MC-ICP-MS) generally follows the method of Foster³¹ with some modifications. The cleaned foraminifera shells were dissolved in 0.5 M HNO₃, and buffered by 2 M NH₄Ac, instead of NaAc-HAc mixture, to pH of ~5.5. We changed the buffering solution to eliminate potential matrix contamination of Na on the δ¹¹B measurement. The buffered solution was gravitationally dripped into micro-columns, loaded with 20 µL ion exchange resin (Amberlite IRA-743, 63–125 µm size fraction), which was precleaned by 0.5 M HNO₃ and then boron-free deionized water. These micro-columns were tested by processing reference materials (boric acid solutions, NIST SRM 951 and ERM AE-121, without and with addition of CaCO₃ matrix; standard carbonates, NEP-3B) and generating values consistent with published values. After rinsing the resin eight times using Milli-Q water, boron was eluted by five aliquots of 90 µL 0.5 M HNO₃. A sixth aliquot was also added and collected to check for complete boron recovery. Total procedure blanks for each batch of samples were monitored, and were between ~20 and 100 pg.

δ¹¹B was measured on a MC-ICP-MS (Neptune Plus) at ANU using a standard bracketing method similar to Foster²⁹. Following Farmer et al.⁵⁴, we measured boron blanks before every bracketing standard (NIST SRM 951) and sample. We also introduce water aerosol into the spray chamber through a second nebulizer after every standard/sample measurement in addition to the routine rinse, to flush out boron in order to minimize the memory effect of boron. An analytical block is as follows: flush-blank-standard-flush-blank-sample-flush-blank-standard. With the additional water flushing in between, measured blanks for ¹¹B can be kept <1.8% (an average for blanks of all the samples, external standards, and bracketing standards during 5 sessions) of the bracketing standard with 30 ppb of boron. Prior to and during analyses of these samples, repeating measurements of standard materials (NIST SRM 951, ERM AE-121, NEP-3B, and NIST RM 8301f) yield results consistent with their published values (Supplementary Table 2). The external reproducibility is estimated by repeating measurements of standard ERM AE-121 at 30-ppb boron concentration along with the samples (2σ = 0.17‰, n = 12). The boron concentration of the standard is chosen to match the expected median concentration of samples. Three of the foraminiferal samples were divided into two subsamples and processed separately from the cleaning step, and standard deviations of these replicated samples range from 0.08 to 0.27‰ (Supplementary Table 3).

During the late LGM and HS1, G. bulloides δ¹¹B we measured at site MD97-2106 agrees with previous measurements by MC-ICP-MS in the Pacific and Atlantic SAZ²³ and the Subtropical Southwest Pacific⁵⁵, but is on average ~1‰ lower than those from the same site measured on a Negative Thermal Ionization Mass Spectrometry (N-TIMS) by a previous study⁵⁶ (Supplementary Fig. 3). We tentatively attribute such offsets to potential analytical biases between MC-ICP-MS and N-TIMS that, as shown by a previous study, range from 0.5 to 2.7‰ and appear to enlarge for samples with low B/Ca values⁵⁴. Despite that Moy et al.⁵⁶ show different deglacial δ¹¹B and thus surface-water pCO₂ magnitudes, deglacial δpCO₂^SOL and δpCO₂^BIO calculated using their data show similar patterns to those based on our new data (Supplementary Fig. 3).

Carbonate chemistry system calculation

G. bulloides δ¹¹B is converted into δ¹¹B of seawater borate (δ¹¹B_borate) using the calibration from Raitzsch, et al.³⁰: δ¹¹B_borate = (δ¹¹B_{G. bulloides} + 3.58 ± 11.77)/(1.09 ± 0.65). To estimate pH, SST and surface seawater salinity (SSS) are required. SST is estimated from G. bulloides Mg/Ca using the calibration of Elderfield and Ganssen³⁵. SSS is estimated from the global sea-level change following Foster³¹. To calculate seawater pCO₂, seawater alkalinity is estimated from the modern seawater SSS-alkalinity relation²⁰. We then use the CO2sys script⁵⁷ to calculate seawater pCO₂ and other carbonate chemistry parameters including DIC. The 2.3–97.7% uncertainties of seawater pCO₂ are propagated by a 10,000-iteration Monte-Carlo method incorporating uncertainties from δ¹¹B (2σ = 0.17‰), SST (2σ = 1 °C), and SSS (2σ = 0.5), and alkalinity which is sourced from SSS and the modern SSS-alkalinity relation²⁰. Using a different way to estimate alkalinity (Supplementary Fig. 7) does not substantially affect our calculated seawater pCO₂ and its decompositions. For published δ¹¹B records, surface-water pCO₂ is recalculated using the same method as this study to be consistent with our methodology. Final uncertainties shown in Figs. 2 and 3 also incorporate age uncertainties. For site MD97-2106, age uncertainty (1σ ranging from 0.2 to 0.8 ka) is derived from the Undatable script⁵⁸, and for published records, a uniform age uncertainty (1σ) of 0.5 ka is assigned.

We partition the total in-situ surface-water pCO₂ changes (δpCO₂^TOTAL) into two components: solubility-driven (δpCO₂^SOL) and biology-driven (δpCO₂^BIO) components. In the main text, δpCO₂^SOL is derived first, and the different between δpCO₂^TOTAL and δpCO₂^SOL is defined as δpCO₂^BIO. Here, we provide an alternative method to derive δpCO₂^BIO first and subsequently δpCO₂^SOL. Firstly, δpCO₂^TOTAL is calculate the same way as described in the main text. Secondly, we use DIC and alkalinity values (the same as those used for in-situ pCO₂ calculations), but constant SST and SSS values at 18 ka to calculate new surface-water pCO₂. It is important to note that DIC and alkalinity are used as intermediate parameters for calculations, and their values do not need to be accurately quantified to yield well-quantified new pCO₂ values. This is because DIC and alkalinity are inherently linked given constraint from pH (see Yu et al.⁵⁹ for detailed discussions). Thirdly, δpCO₂^BIO is calculated by changes in the newly calculated surface-water pCO₂ relative to 18 ka. Fourthly, δpCO₂^SOL is defined by differencing δpCO₂^TOTAL and δpCO₂^BIO. As can be seen from Supplementary Fig. 8, the two methods yield consistent results, strengthening reliability of our calculation. The small differences between these two methods are due to the non-linear responses of seawater pCO₂ to temperature and DIC changes.

For δpCO₂^SOL, it may be further partitioned into temperature- and salinity-driven components (δpCO₂^T and δpCO₂^S, respectively). We first calculate new surface-water pCO₂ at each age by using constant DIC, alkalinity, and SSS at 18 ka, but varying SST. Then, δpCO₂^T is derived as changes of the newly calculated pCO₂ relative to 18 ka. Afterward, δpCO₂^S is defined as the difference between δpCO₂^SOL and δpCO₂^T_. As can be seen from Supplementary Fig. 5, salinity changes tend to counter temperature effect on pCO₂, but δpCO₂^S are limited to within 10 ppm at all four SAZ sites studied.

Regarding model outputs²⁸, we first calculate δpCO₂^TOTAL between 15 ka and 19 ka, simply by differencing in-situ surface-water pCO₂ values at these times (pCO₂^in-situ,15ka and pCO₂^in-situ,19ka, respectively). We re-calculate surface-water pCO₂ at 15 ka (pCO₂^recalc,15ka) using DIC and alkalinity at 15 ka but using SST and SSS at 19 ka. Similar to proxy data, δpCO₂^BIO and δpCO₂^SOL are calculated by: δpCO₂^BIO = pCO₂^recalc,15ka − pCO₂^in-situ,19ka and δpCO₂^SOL = pCO₂^TOTAL − δpCO₂^BIO.

For modern hydrological data²⁹, monthly δpCO₂^TOTAL, δpCO₂^BIO, and δpCO₂^SOL represent deviations from annual mean values. δpCO₂^TOTAL, δpCO₂^BIO, and δpCO₂^SOL are calculated similarly to those for model results described above. For example, monthly δpCO₂^BIO is calculated using monthly alkalinity and DIC but annual mean SST and SSS, while monthly δpCO₂^SOL is calculated using annual mean alkalinity and DIC but with monthly SST and SSS (Fig. S2).

Foraminifera-bound nitrogen isotope analyses

Sample preparation and measurements of δ¹⁵N follow protocols in Ren et al.⁶⁰. For each sample, >3 mg of G. bulloides shells (250–355 µm size fraction) were picked and crushed under a dissecting microscope. Foraminiferal samples were sonicated in an ultrasonic bath for 5 min with 2% polyphosphate solution, treated in bicarbonate-buffered dithionite−citric acid in an 80 °C water bath for 1 h, and added with basic potassium persulfate solution and autoclaved at 121 °C for 1 h. After every cleaning step, samples were rinsed with deionized water. Cleaned samples were dried overnight at 55 °C. Each sample was weighed (~1.5–3.5 mg) into a combusted glass vial and then dissolved in 3 M HCl to release organic N from the calcite shell. Persulfate oxidation reagent (POR, 0.3 g of 3-time-recrystallized basic potassium persulfate and 0.7 g of NaOH dissolved in 100 mL of deionized water) were added to the dissolved samples which were then autoclaved at 121 °C for 1 h to convert organic N to nitrate. The nitrate concentrations of all POR-oxidized samples were measured to determine N contents after autoclaving using the chemiluminescence method⁶¹. Average N content of the cleaned calcite samples is 3.07 mmol N per gram. Nitrate concentration of POR and its δ¹⁵N were constrained by two organic standards (US Geological Survey (USGS) 40, δ¹⁵N = −4.5‰ vs. air; and a laboratory standard, mixture of 6-aminocaproic acid and glycine, δ¹⁵N = 5.4‰ vs. air) processed along with samples. Nitrate concentration of POR is 0.2 µM, representing 1–3% of the total N in samples.

The denitrifier method was applied to transform dissolved nitrate and nitrite into nitrous oxide (N₂O) gas using a naturally occurring denitrifying bacterial strain, Pseudomonas chlororaphis, which lacks an active form of the enzyme N₂O reductase. After degassing of the bacteria for 3 h, 1.5 mL of the bacterial concentrate was added with 5 nmol of samples acidified to pH of 3-7. Two nitrate reference materials (International Atomic Energy Agency NO₃ reference (IAEA-N3), δ¹⁵N = 4.7‰ vs. air; and USGS 34, δ¹⁵N = −1.8‰ vs. air) were processed along with samples to monitor the bacterial conversion and were later repeatedly measured between samples to check the stability of the mass spectrometry.

δ¹⁵N of foraminiferal samples, together with bacterial blanks and organic standards, were determined by gas chromatography and isotope ratio mass spectrometry using a modified SigBench and MAT253 plus⁶². Due to the small sample size and low N content within foraminifera, no duplicates were made for these samples. Our IAEA-N3 and USGS 34 standards yielded standard deviation (1σ) of 0.06 and 0.07‰, respectively. The standard deviation (1σ) of the organic standards analyzed with these samples is 0.15‰, agreeing with the long-term variability of in-house carbonate standards using homogenized coral samples (±0.25‰). As a result, we assume that the analytical error for the δ¹⁵N_FB is 0.25‰ in our new record.

Data availability

All data generated in this study have been deposited in the Zenodo database under access code: https://doi.org/10.5281/zenodo.6970032. All data generated in this study are also provided in the Supplementary Information.

Code availability

Codes used to produce Figs. 1 and 4 are available from Y.D. upon request. Mode output data used to produce Fig. 4 is available from https://doi.org/10.4225/41/5af39aae7960f²⁸.

References

Sigman, D. M., Hain, M. P. & Haug, G. H. The polar ocean and glacial cycles in atmospheric CO₂ concentration. Nature 466, 47–55 (2010).
Article ADS CAS PubMed Google Scholar
Sigman, D. M. & Boyle, E. A. Glacial/interglacial variations in atmospheric carbon dioxide. Nature 407, 859–869 (2000).
Article ADS CAS PubMed Google Scholar
Yu, J. et al. Millennial and centennial CO₂ release from the Southern Ocean during the last deglaciation. Nat. Geosci. 15, 293–299 (2022).
Article ADS CAS Google Scholar
Yu, J. et al. Loss of carbon from the deep sea since the Last Glacial Maximum. Science 330, 1084–1087 (2010).
Article ADS CAS PubMed Google Scholar
Talley, L. D. Descriptive Physical Oceanography: An Introduction (Academic Press, 2011).
Rintoul, S. R. The global influence of localized dynamics in the Southern Ocean. Nature 558, 209–218 (2018).
Article ADS CAS PubMed Google Scholar
Sarmiento, J., Gruber, N., Brzezinsld, M. & Dunne, J. High-latitude controls of thermocline nutrients and low lattitude biological productivity. Nature 427, 53–56 (2004).
Article ADS CAS Google Scholar
Brovkin, V., Ganopolski, A., Archer, D. & Rahmstorf, S. Lowering of glacial atmospheric CO₂ in response to changes in oceanic circulation and marine biogeochemistry. Paleoceanography 22, PA4202 (2007).
Article ADS Google Scholar
Hain, M. P., Sigman, D. M. & Haug, G. H. Carbon dioxide effects of Antarctic stratification, North Atlantic Intermediate Water formation, and subantarctic nutrient drawdown during the last ice age: diagnosis and synthesis in a geochemical box model. Glob. Biogeochem. Cycles 24, GB4023 (2010).
Article ADS CAS Google Scholar
Jaccard, S. L. et al. Two modes of change in southern ocean productivity over the past million years. Science 339, 1419–1423 (2013).
Article ADS CAS PubMed Google Scholar
Martínez-García, A. et al. Iron fertilization of the Subantarctic Ocean during the last ice age. Science 343, 1347–1350 (2014).
Article ADS PubMed CAS Google Scholar
Takahashi, T. Global sea-air CO₂ flux based on climatological surface ocean pCO₂, and seasonal biological and temperature effects. Deep Sea Res. Part II 49, 1601–1622 (2002).
Article ADS CAS Google Scholar
Takahashi, T. et al. Climatological mean and decadal change in surface ocean pCO₂, and net sea–air CO₂ flux over the global oceans. Deep Sea Res. Part II 56, 554–577 (2009).
Article ADS CAS Google Scholar
Volk, T. & Hoffert, M. I. The Carbon Cycle and Atmospheric CO₂: Natural Variations Archean to Present Vol. 32, 99–110 (the American Geophysical Union, 1985).
Hain, M., Sigman, D. & Haug, G. in Treatise on Geochemistry 2nd ed., Vol. 8, 485–517 (Elsevier, 2014).
Takahashi, T., olafsson, J., Goddard, J. G., Chipman, D. W. & Sutherland, S. C. Seasonal variation of CO₂ and nutrients in the high‐latitude surface oceans: a comaprative study. Glob. Biogeochem. Cycles 7, 843–878 (1993).
Article ADS CAS Google Scholar
Khatiwala, S., Schmittner, A. & Muglia, J. Air-sea disequilibrium enhances ocean carbon storage during glacial periods. Sci. Adv. 5, eaaw4981 (2019).
Article ADS CAS PubMed PubMed Central Google Scholar
Köhler, P., Fischer, H., Munhoven, G. & Zeebe, R. E. Quantitative interpretation of atmospheric carbon records over the last glacial termination. Glob. Biogeochem. Cycles 19, GB4020 (2005).
Article ADS CAS Google Scholar
Heinze, C., Maier-Reimer, E. & Winn, K. Glacial pCO₂ reduction by the world ocean: experiments with the hamburg carbon cycle model. Paleoceanography 6, 395–430 (1991).
Article ADS Google Scholar
Sarmiento, J. L. & Gruber, N. Ocean Biogeochemical Dynamics (Princeton University Press, 2006).
Wang, X. T. et al. Deep-sea coral evidence for lower Southern Ocean surface nitrate concentrations during the last ice age. Proc. Natl Acad. Sci. USA 114, 3352–3357 (2017).
Article ADS CAS PubMed PubMed Central Google Scholar
Martinez-Boti, M. A. et al. Boron isotope evidence for oceanic carbon dioxide leakage during the last deglaciation. Nature 518, 219–222 (2015).
Article ADS CAS PubMed Google Scholar
Shuttleworth, R. et al. Early deglacial CO₂ release from the Sub-Antarctic Atlantic and Pacific oceans. Earth Planet. Sci. Lett. 554, 116649 (2021).
Article CAS Google Scholar
Martinez-Garcia, A. et al. Southern Ocean dust-climate coupling over the past four million years. Nature 476, 312–315 (2011).
Article ADS CAS PubMed Google Scholar
Pedro, J. B. et al. The spatial extent and dynamics of the Antarctic Cold Reversal. Nat. Geosci. 9, 51–55 (2015).
Article ADS CAS Google Scholar
Jouzel, J. et al. Orbital and millennial Antarctic climate variability over the past 800,000 years. Science 317, 793–796 (2007).
Article ADS CAS PubMed Google Scholar
Benz, V., Esper, O., Gersonde, R., Lamy, F. & Tiedemann, R. Last Glacial Maximum sea surface temperature and sea-ice extent in the Pacific sector of the Southern Ocean. Quat. Sci. Rev. 146, 216–237 (2016).
Article ADS Google Scholar
Menviel, L. et al. Southern Hemisphere westerlies as a driver of the early deglacial atmospheric CO₂ rise. Nat. Commun. 9, 2503 (2018).
Article ADS CAS PubMed PubMed Central Google Scholar
Gregor, L. & Gruber, N. OceanSODA-ETHZ: a global gridded data set of the surface ocean carbonate system for seasonal to decadal studies of ocean acidification. Earth Syst. Sci. Data 13, 777–808 (2021).
Article ADS Google Scholar
Raitzsch, M. et al. Boron isotope-based seasonal paleo-pH reconstruction for the Southeast Atlantic – a multispecies approach using habitat preference of planktonic foraminifera. Earth Planet. Sci. Lett. 487, 138–150 (2018).
Article ADS CAS Google Scholar
Foster, G. L. Seawater pH, pCO₂ and [CO₃²⁻] variations in the Caribbean Sea over the last 130 kyr: A boron isotope and B/Ca study of planktic foraminifera. Earth Planet. Sci. Lett. 271, 254–266 (2008).
Article ADS CAS Google Scholar
Bostock, H. C., Hayward, B. W., Neil, H. L., Sabaa, A. T. & Scott, G. H. Changes in the position of the Subtropical Front south of New Zealand since the last glacial period. Paleoceanography 30, 824–844 (2015).
Article ADS Google Scholar
Sikes, E. L. et al. Southern Ocean seasonal temperature and Subtropical Front movement on the South Tasman Rise in the late Quaternary. Paleoceanography 24, PA2201 (2009).
Article ADS Google Scholar
Belkin, I. M. & Gordon, A. L. Southern Ocean fronts from the Greenwich meridian to Tasmania. J. Geophys. Res. Oceans 101, 3675–3696 (1996).
Article ADS Google Scholar
Elderfield, H. & Ganssen, G. Past temperature and δ¹⁸O of surface ocean waters inferred from foraminiferal Mg/Ca ratios. Nature 405, 442–445 (2000).
Article ADS CAS PubMed Google Scholar
Dai, Y., Yu, J. & Rafter, P. A. Deglacial ventilation changes in the deep Southwest Pacific. Paleoceanogr. Paleoclimatol 36, e2020PA004172 (2021).
Article ADS Google Scholar
Ren, H. et al. Glacial-to-interglacial changes in nitrate supply and consumption in the subarctic North Pacific from microfossil-bound N isotopes at two trophic levels. Paleoceanography 30, 1217–1232 (2015).
Article ADS Google Scholar
Ren, H., Sigman, D. M., Thunell, R. C. & Prokopenko, M. G. Nitrogen isotopic composition of planktonic foraminifera from the modern ocean and recent sediments. Limnol. Oceanogr. 57, 1011–1024 (2012).
Article ADS CAS Google Scholar
Studer, A. S. et al. Increased nutrient supply to the Southern Ocean during the Holocene and its implications for the pre-industrial atmospheric CO₂ rise. Nat. Geosci. 11, 756–760 (2018).
Article ADS CAS Google Scholar
Studer, A. S. et al. Antarctic Zone nutrient conditions during the last two glacial cycles. Paleoceanography 30, 845–862 (2015).
Article ADS Google Scholar
Ai, X. E. et al. Southern Ocean upwelling, Earth’s obliquity, and glacial-interglacial atmospheric CO₂ change. Science 370, 1348–1352 (2020).
Article ADS CAS PubMed Google Scholar
Li, T. et al. Rapid shifts in circulation and biogeochemistry of the Southern Ocean during deglacial carbon cycle events. Sci. Adv. 6, eabb3807 (2020).
Article ADS CAS PubMed PubMed Central Google Scholar
Monnin, E. et al. Evidence for substantial accumulation rate variability in Antarctica during the Holocene, through synchronization of CO₂ in the Taylor Dome, Dome C and DML ice cores. Earth Planet. Sci. Lett. 224, 45–54 (2004).
Article ADS CAS Google Scholar
Marcott, S. A. et al. Centennial-scale changes in the global carbon cycle during the last deglaciation. Nature 514, 616–619 (2014).
Article ADS CAS PubMed Google Scholar
Lambert, F. et al. Dust-climate couplings over the past 800,000 years from the EPICA Dome C ice core. Nature 452, 616–619 (2008).
Article ADS CAS PubMed Google Scholar
Sachs, J. P. & Anderson, R. F. Fidelity of alkenone paleotemperatures in southern Cape Basin sediment drifts. Paleoceanography 18, 1082 (2003).
Article ADS Google Scholar
Anderson, R. F. et al. Biological response to millennial variability of dust and nutrient supply in the Subantarctic South Atlantic Ocean. Philos. Trans. A Math. Phys. Eng. Sci. 372, 20130054 (2014).
ADS PubMed Google Scholar
Garcia, H. E. et al. World Ocean Atlas 2018. Vol. 4: dissolved inorganic nutrients (phosphate, nitrate and nitrate+nitrite, silicate). A. Mishonov Technical Editor, NOAA Atlas NESDIS 84, 35pp. https://www.ncei.noaa.gov/sites/default/files/2020-04/woa18_vol4.pdf (2019).
Locarnini, R. A. et al. World Ocean Atlas 2018, Volume 1: Temperature. A. Mishonov, Technical Editor. NOAA Atlas NESDIS 81, 52pp. https://www.ncei.noaa.gov/sites/default/files/2020-04/woa18_vol1.pdf (2019).
Barker, S., Greaves, M. & Elderfield, H. A study of cleaning procedures used for foraminiferal Mg/Ca paleothermometry. Geochem. Geophys. Geosyst. 4, 8407 (2003).
Article ADS CAS Google Scholar
Boyle, E. & Keigwin, L. Comparison of Atlantic and Pacific paleochemical records for the last 215,000 years: Changes in deep ocean circulation and chemical inventories. Earth Planet. Sci. Lett. 76, 135–150 (1985).
Article ADS CAS Google Scholar
Yu, J., Elderfield, H., Greaves, M. & Day, J. Preferential dissolution of benthic foraminiferal calcite during laboratory reductive cleaning. Geochem. Geophys. Geosyst. 8, Q06016 (2007).
Article ADS CAS Google Scholar
Yu, J., Day, J., Greaves, M. & Elderfield, H. Determination of multiple element/calcium ratios in foraminiferal calcite by quadrupole ICP-MS. Geochem. Geophys. Geosyst. 6, Q08P01 (2005).
Article Google Scholar
Farmer, J. R., Hönisch, B. & Uchikawa, J. Single laboratory comparison of MC-ICP-MS and N-TIMS boron isotope analyses in marine carbonates. Chem. Geol. 447, 173–182 (2016).
Article ADS CAS Google Scholar
Shao, J. et al. Atmosphere‐ocean CO₂ exchange across the last deglaciation from the boron isotope proxy. Paleoceanogr. Paleoclimatol. 34, 1650–1670 (2019).
Article ADS Google Scholar
Moy, A. D. et al. Varied contribution of the Southern Ocean to deglacial atmospheric CO₂ rise. Nat. Geosci. 12, 1006–1011 (2019).
Article ADS CAS Google Scholar
Lewis, E., Wallace, D. & Allison, L. J. Program Developed for CO₂ System Calculations (Carbon Dioxide Information Analysis Center, managed by Lockheed Martin Energy Research Corporation for the US Department of Energy Tennessee, 1998).
Lougheed, B. C. & Obrochta, S. P. A rapid, deterministic age-depth modeling routine for geological sequences with inherent depth uncertainty. Paleoceanogr. Paleoclimatol. 34, 122–133 (2019).
Article ADS Google Scholar
Yu, J. et al. More efficient North Atlantic carbon pump during the Last Glacial Maximum. Nat. Commun. 10, 2170 (2019).
Article ADS CAS PubMed PubMed Central Google Scholar
Ren, H. et al. Impact of glacial/interglacial sea level change on the ocean nitrogen cycle. Proc. Natl Acad. Sci. USA 114, E6759–E6766 (2017).
CAS PubMed PubMed Central Google Scholar
Braman, R. S. & Hendrix, S. A. Nanogram nitrite and nitrate determination in environmental and biological materials by vanadium (III) reduction with chemiluminescence detection. Anal. Chem. 61, 2715–2718 (1989).
Article CAS PubMed Google Scholar
Weigand, M. A., Foriel, J., Barnett, B., Oleynik, S. & Sigman, D. M. Updates to instrumentation and protocols for isotopic analysis of nitrate by the denitrifier method. Rapid Commun. Mass Spectrom. 30, 1365–1383 (2016).
Article ADS CAS PubMed Google Scholar

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Acknowledgements

We thank Brad Opdyke and Will Howard for help with arranging core materials, and Laurie Menviel for providing model outputs. This work is supported by NSFC42076056 and ARC Discovery Project DP190100894 to J.Y., and Ministry of Science and Technology, Taiwan (111-2636-M-002-020) to H.R.

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Open access funding provided by Lund University.

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Yuhao Dai
Present address: Department of Geology, Lund University, Lund, Sweden

Authors and Affiliations

Research School of Earth Sciences, The Australian National University, Canberra, ACT, Australia
Yuhao Dai, Jimin Yu & Xuan Ji
Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao, China
Jimin Yu
Department of Geosciences, National Taiwan University, Taipei, Taiwan
Haojia Ren

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Yuhao Dai
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Jimin Yu
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Xuan Ji
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Contributions

J.Y. designed the project. Y.D. derived the pCO₂ decomposition method. Y.D. made boron isotope measurements. X.J. made new trace element measurements. J.Y. supervised geochemical measurements made by Y.D. and X.J. H.R. made nitrogen isotope measurements. Y.D. performed data analyses and visualization. Y.D. wrote the first draft of the manuscript with significant inputs from J.Y. All authors contributed to the interpretation of the data and refinement of the manuscript.

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Correspondence to Yuhao Dai or Jimin Yu.

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Dai, Y., Yu, J., Ren, H. et al. Deglacial Subantarctic CO₂ outgassing driven by a weakened solubility pump. Nat Commun 13, 5193 (2022). https://doi.org/10.1038/s41467-022-32895-9

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Received: 09 July 2022
Accepted: 23 August 2022
Published: 03 September 2022
DOI: https://doi.org/10.1038/s41467-022-32895-9

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