| 1. |
- Emile-Geay, J., et al.
(författare)
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Data Descriptor: A global multiproxy database for temperature reconstructions of the Common Era
- 2017
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Ingår i: Scientific Data. - : Springer Science and Business Media LLC. - 2052-4463. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with HadCRUT4.2 surface temperature over the period 1850-2014. Global temperature composites show a remarkable degree of coherence between high-and low-resolution archives, with broadly similar patterns across archive types, terrestrial versus marine locations, and screening criteria. The database is suited to investigations of global and regional temperature variability over the Common Era, and is shared in the Linked Paleo Data (LiPD) format, including serializations in Matlab, R and Python. Since the pioneering work of D'Arrigo and Jacoby1-3, as well as Mann et al. 4,5, temperature reconstructions of the Common Era have become a key component of climate assessments6-9. Such reconstructions depend strongly on the composition of the underlying network of climate proxies10, and it is therefore critical for the climate community to have access to a community-vetted, quality-controlled database of temperature-sensitive records stored in a self-describing format. The Past Global Changes (PAGES) 2k consortium, a self-organized, international group of experts, recently assembled such a database, and used it to reconstruct surface temperature over continental-scale regions11 (hereafter, ` PAGES2k-2013'). This data descriptor presents version 2.0.0 of the PAGES2k proxy temperature database (Data Citation 1). It augments the PAGES2k-2013 collection of terrestrial records with marine records assembled by the Ocean2k working group at centennial12 and annual13 time scales. In addition to these previously published data compilations, this version includes substantially more records, extensive new metadata, and validation. Furthermore, the selection criteria for records included in this version are applied more uniformly and transparently across regions, resulting in a more cohesive data product. This data descriptor describes the contents of the database, the criteria for inclusion, and quantifies the relation of each record with instrumental temperature. In addition, the paleotemperature time series are summarized as composites to highlight the most salient decadal-to centennial-scale behaviour of the dataset and check mutual consistency between paleoclimate archives. We provide extensive Matlab code to probe the database-processing, filtering and aggregating it in various ways to investigate temperature variability over the Common Era. The unique approach to data stewardship and code-sharing employed here is designed to enable an unprecedented scale of investigation of the temperature history of the Common Era, by the scientific community and citizen-scientists alike.
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| 2. |
- Angelopoulus, M., et al.
(författare)
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Physical properties of sea ice cores from site MCS_FYI measured on legs 1 to 3 of the MOSAiC expedition.
- 2022
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Ingår i: PANGAEA.
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We present sea ice temperature and salinity data from first-year ice (FYI) and second-year ice (SYI) relevant to the temporal development of sea ice permeability and brine drainage efficiency from the early growth phase in October 2019 to the onset of spring warming in May 2020. Our dataset was collected in the central Arctic Ocean during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Expedition in 2019 to 2020. MOSAiC was an international transpolar drift expedition in which the German icebreaker RV Polarstern anchored into an ice floe to gain new insights into Arctic climate over a full annual cycle. In October 2019, RV Polarstern moored to an ice floe in the Siberian sector of the Arctic at 85 degrees north and 137 degrees east to begin the drift towards the North Pole and the Fram Strait via the Transpolar Drift Stream. The data presented here were collected during the first three legs of the expedition, so all the coring activities took place on the same floe. The end dates of legs 1, 2, and 3 were 13 December, 24 February, and 4 June, respectively. The dataset contributed to a baseline study entitled, Deciphering the properties of different Arctic ice types during the growth phase of the MOSAiC floes: Implications for future studies. The study highlights downward directed gas pathways in FYI and SYI by inferring sea ice permeability and potential brine release from several time series of temperature and salinity measurements. The physical properties presented in this paper lay the foundation for subsequent analyses on actual gas contents measured in the ice cores, as well as air-ice and ice-ocean gas fluxes. Sea ice cores were collected with a Kovacs Mark II 9 cm diameter corer. To measure ice temperatures, about 4.5 cm deep holes were drilled into the core (intervals varied by site and leg) . The temperatures were measured by a digital thermometer within minutes after the cores were retrieved. The ice cores were placed into pre-labelled plastic sleeves sealed at the bottom end. The ice cores were transported to RV Polarstern and stored in a -20 degrees Celsius freezer. Each of the cores was sub-sampled, melted at room temperature, and processed for salinity within one or two days. The practical salinity was estimated by measuring the electrical conductivity and temperature of the melted samples using a WTW Cond 3151 salinometer equipped with a Tetra-Con 325 four-electrode conductivity cell. The practical salinity represents the the salinity estimated from the electrical conductivity of the solution. The dataset also contains derived variables, including sea ice density, brine volume fraction, and the Rayleigh number.
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| 3. |
- Angelopoulus, M., et al.
(författare)
-
Physical properties of sea ice cores from site MCS-SYI measured on legs 1 to 3 of the MOSAiC expedition
- 2022
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Ingår i: PANGAEA.
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We present sea ice temperature and salinity data from first-year ice (FYI) and second-year ice (SYI) relevant to the temporal development of sea ice permeability and brine drainage efficiency from the early growth phase in October 2019 to the onset of spring warming in May 2020. Our dataset was collected in the central Arctic Ocean during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Expedition in 2019 to 2020. MOSAiC was an international transpolar drift expedition in which the German icebreaker RV Polarstern anchored into an ice floe to gain new insights into Arctic climate over a full annual cycle. In October 2019, RV Polarstern moored to an ice floe in the Siberian sector of the Arctic at 85 degrees north and 137 degrees east to begin the drift towards the North Pole and the Fram Strait via the Transpolar Drift Stream. The data presented here were collected during the first three legs of the expedition, so all the coring activities took place on the same floe. The end dates of legs 1, 2, and 3 were 13 December, 24 February, and 4 June, respectively. The dataset contributed to a baseline study entitled, Deciphering the properties of different Arctic ice types during the growth phase of the MOSAiC floes: Implications for future studies. The study highlights downward directed gas pathways in FYI and SYI by inferring sea ice permeability and potential brine release from several time series of temperature and salinity measurements. The physical properties presented in this paper lay the foundation for subsequent analyses on actual gas contents measured in the ice cores, as well as air-ice and ice-ocean gas fluxes. Sea ice cores were collected with a Kovacs Mark II 9 cm diameter corer. To measure ice temperatures, about 4.5 cm deep holes were drilled into the core (intervals varied by site and leg) . The temperatures were measured by a digital thermometer within minutes after the cores were retrieved. The ice cores were placed into pre-labelled plastic sleeves sealed at the bottom end. The ice cores were transported to RV Polarstern and stored in a -20 degrees Celsius freezer. Each of the cores was sub-sampled, melted at room temperature, and processed for salinity within one or two days. The practical salinity was estimated by measuring the electrical conductivity and temperature of the melted samples using a WTW Cond 3151 salinometer equipped with a Tetra-Con 325 four-electrode conductivity cell. The practical salinity represents the the salinity estimated from the electrical conductivity of the solution. The dataset also contains derived variables, including sea ice density, brine volume fraction, and the Rayleigh number.
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| 4. |
- Divine, D. V., et al.
(författare)
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Deuterium excess record from a small Arctic ice cap
- 2008
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 113:D19, s. D19104-
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a deuterium excess (d) record from an ice core drilled on a small ice cap in Svalbard in 1997. The core site is located at Lomonosovfonna at 1255 m asl, and the analyzed time series spans the period 1400-1990 A. D. The record shows pronounced multidecadal to centennial-scale variations coherent with sea surface temperature changes registered in the subtropical to southern middle-latitude North Atlantic during the instrumental period. We interpret the negative trend in the deuterium excess during the 1400s and 1500s as an indication of cooling in the North Atlantic associated with the onset of the Little Ice Age. Consistently positive anomalies of d after 1900, peaking at about 1950, correspond with well-documented contemporary warming. Yet the maximum values of deuterium excess during 1900-1990 are not as high as in the early part of the record (pre-1550). This suggests that the sea surface temperatures during this earlier period of time in the North Atlantic to the south of approximately 45 degrees N were at least comparable with those registered in the 20th century before the end of the 1980s. We examine the potential for a cold bias to exist in the deuterium excess record due to increased evaporation from the local colder sources of moisture having isotopically cold signature. It is argued that despite a recent oceanic warming, the contribution from this local moisture to the Lomonosovfonna precipitation budget is still insufficient to interfere with the isotopic signal from the primary moisture region in the midlatitude North Atlantic.
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| 5. |
- Gruen, E., et al.
(författare)
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Ulysses Dust Detection System V3.1
- 2010
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Ingår i: NASA Planetary Data System. ; 140
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Tidskriftsartikel (refereegranskat)abstract
- This data set contains the data from the Ulysses dust detector system (UDDS) from start of mission through the end of mission, 1990-2007. (As the dust detector was turned off after Nov. 30, 2007, this is the last date for which UDDS data is recorded.) Included are the dust impact data, noise data, laboratory calibration data, and location and orientation of the spacecraft and instrument.
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| 6. |
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| 7. |
- Salganik, E., et al.
(författare)
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Temporal evolution of under-ice meltwater layers and false bottoms and their impact on summer Arctic sea ice mass balance
- 2023
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Ingår i: Elementa: Science of the Anthropocene. - 2325-1026. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Low-salinity meltwater from Arctic sea ice and its snow cover accumulates and creates under-ice meltwater layers below sea ice. These meltwater layers can result in the formation of new ice layers, or false bottoms, at the interface of this low-salinity meltwater and colder seawater. As part of the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC), we used a combination of sea ice coring, temperature profiles from thermistor strings and underwater multibeam sonar surveys with a remotely operated vehicle (ROV) to study the areal coverage and temporal evolution of under-ice meltwater layers and false bottoms during the summer melt season from mid-June until late July. ROV surveys indicated that the areal coverage of false bottoms for a part of the MOSAiC Central Observatory (350 by 200 m2) was 21%. Presence of false bottoms reduced bottom ice melt by 7-8% due to the local decrease in the ocean heat flux, which can be described by a thermodynamic model. Under-ice meltwater layer thickness was larger below first-year ice and thinner below thicker second-year ice. We also found that thick ice and ridge keels confined the areas in which under-ice meltwater accumulated, preventing its mixing with underlying seawater. While a thermodynamic model could reproduce false bottom growth and melt, it could not describe the observed bottom melt rates of the ice above false bottoms. We also show that the evolution of under-ice meltwaterlayer salinity below first-year ice is linked to brine flushing from the above sea ice and accumulating in the meltwater layer above the false bottom. The results of this study aid in estimating the contribution of underice meltwater layers and false bottoms to the mass balance and salt budget for Arctic summer sea ice.
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| 8. |
- Schleussner, C. -F., et al.
(författare)
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Indications for a North Atlantic ocean circulation regime shift at the onset of the Little Ice Age
- 2015
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Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 45:11-12, s. 3623-3633
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Tidskriftsartikel (refereegranskat)abstract
- A prominent characteristic of the reconstructed Northern Hemisphere temperature signal over the last millennium is the transition from the Medieval Climate Anomaly to the Little Ice Age (LIA). Here we report indications for a non-linear regime shift in the North Atlantic ocean circulation at the onset of the LIA. Specifically, we apply a novel statistical test based on horizontal visibility graphs to two ocean sediment August sea-surface temperature records from the Norwegian Sea and the central subpolar basin and find robust indications of time-irreversibility in both records during the LIA onset. Despite a basin-wide cooling trend, we report an anomalous warming in the central subpolar basin during the LIA that is reproduced in ensemble simulations with the climate model of intermediate complexity CLIMBER-3 as a result of a non-linear regime shift in the subpolar North Atlantic ocean circulation. The identified volcanically triggered non-linear transition in the model simulations provides a plausible explanation for the signatures of time-irreversibility found in the ocean sediment records. Our findings indicate a potential multi-stability of the North Atlantic ocean circulation and its importance for regional climate change on centennial time scales.
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| 9. |
- Divine, D. V., et al.
(författare)
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Modelling the regional climate and isotopic composition of Svalbard precipitation using REMOiso : a comparison with available GNIP and ice core data
- 2011
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 25:24, s. 3748-3759
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Tidskriftsartikel (refereegranskat)abstract
- Simulations of a regional (approx. 50 km resolution) circulation model REMOiso with embedded stable water isotope module covering the period 1958-2001 are compared with the two instrumental climate and four isotope series (d18O) from western Svalbard. We examine the data from ice cores drilled on Svalbard ice caps in 1997 (Lomonosovfonna, 1250 m asl) and 2005 (Holtedahlfonna, 1150 m asl) and the GNIP series from Ny-angstrom lesund and Isfjord Radio. The surface air temperature (SAT) and precipitation data from Longyearbyen and Ny-angstrom lesund are used to assess the skill of the model in reproducing the local climate. The model successfully captures the climate variations on the daily to multidecadal times scales although it tends to systematically underestimate the winter SAT. Analysis suggests that REMOiso performs better at simulating isotope compositions of precipitation in the winter than summer. The simulated and measured Holtedahlfonna d18O series agree reasonably well, whereas no significant correlation has been observed between the modelled and measured Lomonosovfonna ice core isotopic series. It is shown that sporadic nature as well as variability in the amount inherent in precipitation process potentially limits the accuracy of the past SAT reconstruction from the ice core data. This effect in the study area is, however, diminished by the role of other factors controlling d18O in precipitation, most likely sea ice extent, which is directly related with the SAT anomalies.
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| 10. |
- Orme, L. C., et al.
(författare)
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Climatic impacts on an Arctic lake since 1300 AD : a multi-proxy lake sediment reconstruction from Prins Karls Forland, Svalbard
- 2023
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Ingår i: Journal of Paleolimnology. - : Springer Science and Business Media LLC. - 0921-2728 .- 1573-0417. ; 69:3, s. 249-266
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Tidskriftsartikel (refereegranskat)abstract
- On the remote Arctic archipelago of Svalbard, there is increasing evidence of environmental impacts from climate change. The analysis of lake sedimentary records can be used to assess how strongly these recent changes have altered lake ecosystems. Sediments deposited during the last millennium from Lake Blokkvatnet, Prins Karls Forland, were analysed using a multiproxy approach, including stable isotope and X-ray fluorescence analysis. The results were interpreted as reflecting variability of (1) soil organic matter inwash, and potentially catchment and lake primary production, and (2) catchment weathering and erosion. Organic content began increasing after 1920 AD to the present, likely in response to warming. Earlier peaks of a similar magnitude occurred on three occasions since 1300 AD, with evidence indicating that these may have coincided with multidecadal-scale periods with higher temperatures, reduced sea ice and negative phases of the North Atlantic Oscillation. Catchment weathering and fluvial erosion began to increase around 1800 AD and peaked during the early twentieth century, potentially due to rising temperatures in autumn and winter causing increased liquid water availability. The records suggest that similar levels of erosion and weathering occurred between approximately 1300 and 1600 AD, spanning the transition from the Medieval Climate Anomaly to the Little Ice Age.
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