Climate of The Past Discussions最新文献

{"title":"Spring onset and seasonality patterns during the Lateglacial in the eastern Baltic region","authors":"L. Amon, F. Wagner-Cremer, J. Vassiljev, S. Veski","doi":"10.5194/CP-2021-133","DOIUrl":"https://doi.org/10.5194/CP-2021-133","url":null,"abstract":"Abstract. Spring onset is an important phenological observation that is sensitive to modern climate change and can be traced back in geological time. The Lateglacial (~14500–11700 cal yr BP) spring onset and growing season (growth-degree-days) dynamics in the eastern Baltic region were reconstructed using the micro-phenological approach based on the dwarf birch (Betula nana) subfossil leaf cuticles. The presented study sites, Lake Lielais Svetinu (eastern Latvia) and Lake Kosilase (central Estonia), are located ~200 km apart in the region affected by the south-eastern sector of the Scandinavian Ice Sheet. During the Lateglacial period the region and its biota were influenced by the retreating glacier and the different stages of the Baltic Ice Lake. The plant macrofossil data confirms that the study sites were located in different vegetation zones (arctic-to-boreal) during the Lateglacial period. The dynamics of the estimated length of the growing season and spring onset, combined with the regional collection of plant macrofossil records, suggest the importance of local settings to species migration. During the Lateglacial warming period (Bolling/Allerod), a notable spring warming and longer growing season was calculated based on micro-phenology, but the treeline did not extend beyond central Estonia. The comparison of pollen- and chironomid-inferred past temperature estimations with spring onset, growth-degree-days, and plant macrofossil data shows coherent patterns during the cooler Older Dryas and warmer Bolling/ Allerod periods while suggesting more complicated climate dynamics and possible warmer episodes during the Younger Dryas cold reversal.","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117114744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simulated range of mid-Holocene precipitation changes to extended lakes and wetlands over North Africa","authors":"N. Specht, M. Claussen, T. Kleinen","doi":"10.5194/cp-2021-129","DOIUrl":"https://doi.org/10.5194/cp-2021-129","url":null,"abstract":"Abstract. Enhanced summer insolation over North Africa induced a monsoon precipitation increase during the mid-Holocene, about 6000 years ago, and led to a widespread expansion of lakes and wetlands in the present-day Sahara. This expansion of lakes and wetlands is documented in paleoenvironmental sediment records, but the spatially sparse and often discontinuous sediment records provide only a fragmentary picture. Former simulation studies prescribed either a small lake and wetland extent from reconstructions or focused on documented mega-lakes only to investigate their effect on the mid-Holocene climate. In contrast to these studies, we investigate the possible range of mid-Holocene precipitation changes in response to a small lake extent and a potential maximum lake and wetland extent.  Results show that the maximum lake and wetland extent shift the North African rain belt about 3 ° farther northward than the small lake extent. Vegetated wetlands cause a larger precipitation increase than the equally-large lakes due to their high surface roughness. A moisture budget analysis reveals that both, lakes and wetlands, cause an enhanced inland moisture transport and local moisture recycling to their southern side. In contrast, increased moisture advection by the Harmattan winds causes a drying response to the north of the lakes and wetlands. These results indicate that the latitudinal position of the lakes and wetlands influences the northward extension of the African summer monsoon. In the sensitivity experiments, the northern position of West Saharan lakes and wetlands substantially contributes to the strong monsoon northward shift seen in the maximum lake and wetland simulations.","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"121 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116570917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Supplementary material to \"Low-latitude climate change linked to high-latitude glaciation during the Late Paleozoic Ice Age: evidence from the terrigenous detrital kaolinite\"","authors":"Peixin Zhang, Jing Lu, Minfang Yang, L. Shao, Zi-Zhen Wang, J. Hilton","doi":"10.5194/cp-2021-108-supplement","DOIUrl":"https://doi.org/10.5194/cp-2021-108-supplement","url":null,"abstract":"Abstract. The Late Paleozoic Ice Age (LPIA; ca. 360–260 million years ago) was one of the most significant glacial events in Earth history that records cycles of ice advance and retreat in southern high-latitude Gondwana and provides a deep-time perspective for climate-glaciation coevolution. However, climate records from the LIPA are poorly understood in low latitudes, particularly in the North China Plate (NCP) on the eastern Palaeo-Tethys. We address this through a detailed mineralogical study of the marine-continental sedimentary succession in the Yuzhou Coalfield from the southern NCP in which we apply Zircon U-Pb dating, biostratigraphy, and high-resolution clay mineral composition to reconstruct latest Carboniferous to early Permian chronostratigraphy and climate change. The Benxi, Taiyuan, and Shanxi formations in the study area are assigned to the Gzhelian, Asselian-Artinskian, and Kungurian-Roadian stages respectively and the Carboniferous Permian lithostratigraphy across NCP recognized as widely diachronous. Detrital micromorphology of kaolinite under scanning electron microscopy and illite crystallization indicates kaolinite contents to be a robust proxy for palaeoclimate reconstruction. Kaolinite data show alternating warm-humid and cool-humid climate conditions that are roughly consistent with the calibrated glacial-interglacial successions recognized in high-latitude eastern Australia, including the glaciations P1 (Asselian-early Sakmarian) and P2 (late Sakmarian-early Artinskian), as well as the climatic transition to glaciation P3 (Roadian). Our results indicate a comparatively cool-humid and warm-humid climate mode in low-latitude NCP during glacial and interglacial periods, and this is a significant step toward connecting climate change in low-latitudes to high-latitude glaciation during the LPIA.\u0000","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128119976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Holocene wildfire regimes in forested peatlands in western Siberia: interaction between peatland moisture conditions and the composition of plant functional types","authors":"A. Feurdean, A. Diaconu, M. Pfeiffer, M. Gałka, S. Hutchinson, Geanina Butiseaca, N. Gorina, S. Tonkov, A. Niamir, I. Tanțău, S. Kirpotin","doi":"10.5194/cp-2021-125","DOIUrl":"https://doi.org/10.5194/cp-2021-125","url":null,"abstract":"Abstract. Wildfire is the most common disturbance type in boreal forests and can trigger significant changes in forest composition. Waterlogging in peatlands determines the degree of tree cover and the depth of the burning horizon associated with wildfires. However, interactions between peatland moisture, vegetation composition and flammability, and fire regime in forested peatland in Eurasia remain largely unexplored, despite their huge extent in boreal regions. To address this knowledge gap, we reconstructed the Holocene fire regime, vegetation composition, and peatland hydrology at two sites in Western Siberia near Tomsk Oblast, Russia. The palaeoecological records originate from forested peatland areas in predominantly light taiga (Pinus-Betula) with the increase in dark taiga communities (Pinus sibirica, Picea obovata, Abies sibirica) towards the east. We found that the past water level fluctuated between 8 and 30 cm below the peat surface. Wet peatland conditions promoted broadleaf trees (Betula), whereas dry peatland conditions favoured conifers and a greater forest density (dark-to-light-taiga ratio). The frequency and severity of fire increased with a declining water table that enhanced fuel dryness and flammability and at an intermediate forest density. We found that the probability of intensification in fire severity increased when the water level declined below 20 cm suggesting a tipping point in peatland hydrology at which wildfire regime intensifies. On a Holocene scale, we found two scenarios of moisture-vegetation-fire interactions. In the first, severe fires were recorded between 7.5 and 4.5 ka BP with lower water levels and an increased proportion of dark taiga and fire avoiders (Pinus sibirica at Rybanya and Abies sibirica at Ulukh Chayakh) mixed into the dominantly light taiga and fire-resister community of Pinus sylvestris. The second occurred over the last 1.5 ka and was associated with fluctuating water tables, a declining abundance of fire avoiders, and an expansion of fire invaders (Betula). These findings suggest that frequent high-severity fires can lead to compositional and structural changes in forests when trees fail to reach reproductive maturity between fire events or where extensive forest gaps limit seed dispersal. This study also shows prolonged periods of synchronous fire activity across the sites, particularly during the early to mid-Holocene, suggesting a regional imprint of centennial to millennial-scale Holocene climate variability on wildfire activity. Increasing human presence in the region of the Ulukh-Chayakh Mire near Teguldet over the last four centuries drastically enhanced ignitions compared to natural background levels. Frequent warm and dry spells predicted for the future in Siberia by climate change scenarios will enhance peatland drying and may convey a competitive advantage to conifer taxa. However, dry conditions, particularly a water table decline below the threshold of 20 cm, will probably e","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125908838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Summer sea-ice variability on the Antarctic margin during the last glacial period reconstructed from snow petrel (Pagodroma nivea) stomach-oil deposits","authors":"E. McClymont, M. J. Bentley, D. Hodgson, C. Spencer-Jones, Thomas Wardley, Martin D. West, I. Croudace, S. Berg, D. Gröcke, G. Kuhn, S. Jamieson, L. Sime, R. Phillips","doi":"10.5194/cp-2021-134","DOIUrl":"https://doi.org/10.5194/cp-2021-134","url":null,"abstract":"Abstract. Antarctic sea ice is a critical component of the climate system, affecting a range of physical and biogeochemical feedbacks, and supporting unique ecosystems. During the last glacial stage, Antarctic sea ice was more extensive than today, but uncertainties in geological (marine sediments), glaciological (ice core), and climate model reconstructions of past sea-ice extent continue to limit our understanding of its role in the Earth system. Here, we present a novel archive of past sea-ice environments from regurgitated stomach oils of snow petrels (Pagodroma nivea), preserved at nesting sites in Dronning Maud Land, Antarctica. We show that by combining information from fatty acid distributions and their stable carbon isotope ratios with measurements of bulk carbon and nitrogen stable isotopes and trace metal data, it is possible to reconstruct changing snow petrel diet within Marine Isotope Stage 2 (ca. 22.6–28.8 cal. kyr BP). We show that, as today, a mixed diet of krill and fish characterises much of the record. However, between 25.7–26.8 cal. kyr BP signals of krill almost disappear. By linking dietary signals in the stomach-oil deposits to modern feeding habits and foraging ranges, we infer the use by snow petrels of open water habitats (‘polynyas’) in the sea ice during our interval of study. The periods when consumption of krill was reduced are interpreted to correspond to the opening of polynyas over the continental shelf, which became the preferred foraging habitat. Our results challenge hypotheses that the development of extensive, thick, multi-year sea-ice close to the continent was a key driver of positive sea ice-climate feedbacks during glacial stages, and highlight the potential of stomach-oil deposits as a palaeo-environmental archive of Southern Ocean conditions.\u0000","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126702923","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Climate history of the principality of Transylvania during the Maunder Minimum (MM) years (1645–1715 CE)","authors":"M. Stangl, U. Foelsche","doi":"10.5194/cp-2021-117","DOIUrl":"https://doi.org/10.5194/cp-2021-117","url":null,"abstract":"Abstract. This paper deals with the climate in the former Grand Duchy of Transylvania, now one of the three major geographical provinces of Romania, within the so-called Maunder Minimum (MM) (1645–1715), an astrophysically defined part of the Little Ice Age (LIA), which was characterized by reduced solar activity. The historical data from Transylvania are compared with that from Germany, Austria and Switzerland. This comparison for the period 1645–1715 shows good agreement but also reveals geographic characteristics of the region. For the first time, we present here a comparison between the four geographic areas in text and tabular form. Quotes from mostly German-language sources are reproduced in English translation. Furthermore, we examine for a longer period (1500–1950) the extent to which the climate of Transylvania might have been affected by long-term fluctuations in solar activity, as deduced from isotopic reconstructions from ice cores. This comparison suggests a certain solar influence but the agreement is not very pronounced. Future investigation in a pan-European context is needed to reach reliable statements. Some results are unexpected – like an unusually small number of severe winters during the last decades of the MM, where extreme cold was restricted to a few years, like the extreme winters 1699/1700 and 1708/1709.\u0000","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"144 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133506882","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Supplementary material to \"Late Paleocene CO2 drawdown, climatic cooling, and terrestrial denudation in the southwest Pacific\"","authors":"C. Hollis, S. Naeher, C. Clowes, J. Dahl, Xun Li, B. Naafs, R. Pancost, K. Taylor, G. Ventura, R. Sykes","doi":"10.5194/cp-2021-122-supplement","DOIUrl":"https://doi.org/10.5194/cp-2021-122-supplement","url":null,"abstract":"Abstract. Late Paleocene deposition of an organic-rich sedimentary facies on the continental shelf and slope of New Zealand and eastern Australia has been linked to short-lived climatic cooling and terrestrial denudation following sea-level fall. Recent studies have confirmed that the organic matter in this facies, termed Waipawa organofacies, is primarily of terrestrial origin, with a minor marine component. It is also unusually enriched in δ13C. In this study we aim to determine the cause or causes of this enrichment. For Waipawa organofacies and its bounding facies in the Taylor White section, Hawkes Bay, paired palynofacies and δ13C analysis of density fractions indicate that the heaviest δ13C values are associated with degraded phytoclasts (woody plant matter) and that the 13C enrichment is partly due to lignin degradation. Compound specific δ13C analyses of samples from the Taylor White and mid-Waipara (Canterbury) sections confirms this relationship but also reveal a residual 13C enrichment of ~ 2.5 ‰ in higher plant biomarkers (n-alkanes and n-alkanoic acids) and 3–4 ‰ in the subordinate marine component, which we interpret as indicating a significant drawdown of atmospheric CO2. Refined age control for Waipawa organofacies indicates that deposition occurred between 59.2 and 58.4 Ma, which coincides with a Paleocene oxygen isotope maximum (POIM) and the onset of the Paleocene carbon isotope maximum (PCIM). This timing suggests that this depositional event was related to global cooling and carbon burial. This relationship is further supported by published TEX86-based sea surface temperatures that indicate a pronounced regional cooling during deposition. We suggest that reduced greenhouse gas emissions from volcanism and accelerated carbon burial related to several tectonic factors and positive feedbacks resulted in short-lived global cooling, growth of ephemeral ice sheets, and a global fall in sea level. Accompanying erosion and carbonate dissolution in deep sea sediment archives may have hidden the evidence of this \"hypothermal\" event until now.\u0000","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123686078","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Water level change of Lake Machang in eastern China during the past 200 years","authors":"Jie Fei","doi":"10.5194/cp-2021-121","DOIUrl":"https://doi.org/10.5194/cp-2021-121","url":null,"abstract":"Abstract. Lake Machang, which occupies an area of approximately 30 km2 in Jining City of eastern China, was a historical reservoir on the Grand Canal existing from early 15th century to early 20th century. The premodern monthly water level observation of Lake Machang commenced in 1814 AD and ended in 1902 AD. The available observation data from the monthly records could cover 75.6 % of the whole study period 1814–1912. Although the water level was seemingly artificially intervened by human activities, monthly and annual water level changes still correlated well with precipitation. That is, climate is still the dominant factor of water level changes on seasonal and annual scales. The flooding of the Yellow River in 1871 AD carried large amount of silt into Lake Machang, which resulted in the rise of lake bed and reclamation initiated by local residents. In particular, after the reclamation activity was officially approved in 1900 AD, Lake Machang was massively reclaimed and eventually dried up in the early 20th century.\u0000","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128246203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multiple Proxy Estimates of pCO2 in the Hauterivian–Barremian of the Laiyang Basin, Eastern China","authors":"Peihong Jin, Mingzhen Zhang, Xiangtong Lei, Baoxia Du, J. Dong, Bainian Sun","doi":"10.5194/cp-2021-96","DOIUrl":"https://doi.org/10.5194/cp-2021-96","url":null,"abstract":"Abstract. In recent decades, several proxies have been developed to reconstruct atmospheric paleo-CO2 concentrations (pCO2). The confidence in paleo-CO2 estimates can be increased by comparing results from multiple proxies with multiple species at a single site. Here we present a new pCO2 record for the Hauterivian–Barremian using three methods based on two fossil coniferous species (Cupressinocladus sp. and Brachyphyllum obtusum) collected from Laiyang Basin, eastern China. The pCO2 values were approximately 579–663 ppmv (recent standardization) and 966–1106 ppmv (carboniferous standardization) based on the stomatal ratio (SR)-based method, and about 472–525 ppmv based on the mechanistic model. Both of these two methods were highly coincident with other SR-based and geochemical reconstructions for the early stage of the Early Cretaceous. The pCO2 value estimated using the carbon isotopes model was approximately 472–525 ppmv, which is generally lower than the pCO2 valueestimated using the other methods. The mechanistic model may be widely applied to more fossil taxa than the SR-based method and retains sensitivity at high pCO2. Furthermore, by comparing with other pCO2 records and Weissert event in the Early Cretaceous, the pCO2 values obtained from this study indicate a relatively low atmospheric CO2 concentration during the Hauterivian–Barremian, and reflect the cooling event in the last stage of the Weissert event.\u0000","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116638141","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Variations in export production, lithogenic sediment transport and iron fertilization in the Pacific sector of the Drake Passage over the past 400 ka","authors":"María H. Toyos, G. Winckler, H. Arz, L. Lembke‐Jene, C. Lange, G. Kuhn, F. Lamy","doi":"10.5194/cp-2021-85","DOIUrl":"https://doi.org/10.5194/cp-2021-85","url":null,"abstract":"Abstract. Changes in Southern Ocean export production have broad biogeochemical and climatic implications. Specifically, iron fertilization likely increased subantarctic nutrient utilization and enhanced the efficiency of the biological pump during glacials. However, past export production in the subantarctic Southeast Pacific is poorly documented, and its connection to Fe fertilization, potentially related to Patagonian Ice Sheet dynamics is unknown. We report on biological productivity changes over the past 400 ka, based on a combination of 230Thxs-normalized and stratigraphy-based mass accumulation rates of biogenic barium, organic carbon, biogenic opal, and calcium carbonate as indicators of paleo-export production in a sediment core upstream of the Drake Passage. In addition, we use fluxes of iron and lithogenic material as proxies for terrigenous matter, and thus potential micronutrient supply. Stratigraphy-based mass accumulation rates are strongly influenced by bottom-current dynamics, which result in variable sediment focussing or winnowing at our site. Carbonate is virtually absent in the core, except during peak interglacial intervals of the Holocene, and Marine Isotope Stages (MIS) 5 and 11, likely caused by transient decreases in carbonate dissolution. All other proxies suggest that export production increased during most glacial periods, coinciding with high iron fluxes. Such augmented glacial iron fluxes at the core site were most likely derived from glaciogenic input from the Patagonian Ice Sheet promoting the growth of phytoplankton. Additionally, glacial export production peaks are also consistent with northward shifts of the Subantarctic and Polar Fronts, which positioned our site south of the Subantarctic Front and closer to silicic acid-rich waters of the Polar Frontal Zone, as well as a with a decrease in the diatom utilization of Si relative to nitrate under Fe-replete conditions. However, glacial export production near the Drake Passage was lower than in the Atlantic and Indian sectors of the Southern Ocean, which may relate to complete consumption of silicic acid in the study area. Our results underline the importance of micro-nutrient fertilization through lateral terrigenous input from South America rather than aeolian transport, and exemplify the role of frontal shifts and nutrient limitation for past productivity changes in the Pacific entrance to the Drake Passage.\u0000","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115227971","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}