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Record W3191564472

Thermokarst Lagoons - Carbon Pools and Panarctic Distribution

2020· dissertation· en· W3191564472 on OpenAlex
Maren Jenrich

Why this work is in the frame

A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.

aboutThe title or abstract carries a Canadian signal from the geographic lexicon.
no affNo Canadian affiliation: this work is invisible to an affiliation-only frame.
No Canadian affiliation. An affiliation-only frame, the usual design, would never have seen this work. It is one of the works that make the case for inverting the frame.

Bibliographic record

VenueHelmholtz-Zentrum für Polar-und Meeresforschung (Alfred-Wegener-Institut) · 2020
Typedissertation
Languageen
FieldEarth and Planetary Sciences
TopicClimate change and permafrost
Canadian institutionsnot available
Fundersnot available
KeywordsThermokarstPermafrostArcticErosionClimate changeGeologyEnvironmental scienceCoastal erosionSedimentOceanographyHydrology (agriculture)Earth sciencePhysical geographyGeomorphologyGeography
DOInot available

Abstract

fetched live from OpenAlex

The permafrost carbon (C) pool is a major storage component of the terrestrial C cycle and it is vulnerable in a warming climate. Permafrost carbon is mobilized by different processes of thaw and erosion, including thermokarst and thermo-erosion. For example, thermokarst lagoons in the Arctic form along ice-rich permafrost coasts of Siberia, Alaska, and Canada by thaw subsidence, lake formation, and subsequent breaching by coastal erosion and marine inundation of lakes or drained lake basins. Thermokarst lagoon formation is an important step in the process of mobilizing terrestrial permafrost C pools along rapidly changing Arctic coasts. In addition, they affect the temperature and salinity of former thermokarst lake taliks during their transition to the marine environment. During current and future climate change in the Arctic, sea-level rise, accelerated permafrost thaw, intensified coastal erosion and changing sea ice regimes likely will increase the rate of thermokarst lagoon formation. Given the potentially increasing frequency of thermokarst lagoon formation and their rapid effect on permafrost degradation during the transition from a terrestrial to a marine system, it is important to understand how sedimentation regime, permafrost warming, and organic C stocks are affected during this transition. The objective of this master thesis is to asses (1) the sediment and pore water characteristics, (2) the C inventory, and (3) the spatial coverage of such thermokarst lagoon features with a multidisciplinary approach using sedimentological, hydrochemical, biogeochemical and remote sensing techniques. Samples of 30 m long sediment cores from two thermokarst lagoons on the Bykovsky Peninsula (Laptev Sea, Siberia) were analysed to characterise and quantify the C-pools as well as the sediment and pore water properties. The lagoons are examples for two different lagoon systems, an open and a semi-closed lagoon system. GIS and remote sensing tools were used to identify, map, and characterise thermokarst lagoons on a panarctic context along coasts of Siberia, Alaska, and NW Canada. The results showed that salt intrusion into sediments is higher in the open lagoon with electrical conductivities of up to 108mS/cm leading to cryotic talik formation. The total organic C density varies between 2 and 85 kg/m3 for the chosen sites, with higher values found in the class “open system lagoons”. To evaluate the larger-scale spatial relevance of this data, I identified eight lagoons along the southern Laptev Sea coast covering an area of about 18.2 x 106m2 and extrapolated my measured data on C storage to a regional level. I measured 16.5 kg/m3 as the mean for lagoon C density, which is well within the range of the terrestrial yedoma (8 kg/m³) and thermokarst (24 kg/m3) deposits in the yedoma region. Using this lagoon C density mean and the spatial coverage, I calculated 9.4 Mt C in the first 30m of southern Laptev Sea lagoon sediments, which makes it a substantial inventory of formerly frozen but now unfrozen C that has become available for microbial degradation. Along the pan-arctic coast between Taimyr Peninsula in North Siberia and Tuktoyaktuk Peninsula in Northwest Canada I mapped 690 lagoons of which 292 (42%) originated from thermokarst basins indicating the broader relevance of my findings to many regions along the Arctic coast. Thermokarst lagoons along the southern Laptev Sea coast were on average five times larger than non-thermokarst lagoons. The case study on Bykovsky provides an initial estimate of the potential contribution of this highly dynamic degradation process that combines permafrost degradation in both the marine and the terrestrial system.

Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.

Full frame distilled prediction

Teacher imitation

Not calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.

metaresearch head score (Codex)0.000
metaresearch head score (Gemma)0.000
Version: codex-gemma-dda1882f352aValidation status: machine_predicted_unvalidated
Candidate categoriesMeta-epidemiology (narrow), Insufficient payload (model declined to judge)
Consensus categoriesMeta-epidemiology (narrow)
DomainCandidate signal: none · Consensus signal: none
Study designCandidate signal: Observational · Consensus signal: none
GenreCandidate signal: Empirical · Consensus signal: Empirical
Teacher disagreement score0.522
Threshold uncertainty score1.000

Codex and Gemma teacher scores by category

CategoryCodexGemma
Metaresearch0.0000.000
Meta-epidemiology (narrow)0.0010.001
Meta-epidemiology (broad)0.0010.001
Bibliometrics0.0000.001
Science and technology studies0.0010.000
Scholarly communication0.0010.001
Open science0.0010.000
Research integrity0.0010.001
Insufficient payload (model declined to judge)0.0020.000

Machine scores (provisional)

The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.

Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.

Opus teacher head0.024
GPT teacher head0.261
Teacher spread0.238 · how far apart the two teachers sit on this one work
Validation statusscore_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it