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- Davis, P. E. D., et al.
(author)
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Suppressed basal melting in the eastern Thwaites Glacier grounding zone
- 2023
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 614:7948
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Journal article (peer-reviewed)abstract
- Thwaites Glacier is one of the fastest-changing ice-ocean systems in Antarctica(1-3). Much of the ice sheet within the catchment of Thwaites Glacier is grounded below sea level on bedrock that deepens inland(4), making it susceptible to rapid and irreversible ice loss that could raise the global sea level by more than half a metre(2,3,5). The rate and extent of ice loss, and whether it proceeds irreversibly, are set by the ocean conditions and basal melting within the grounding-zone region where Thwaites Glacier first goes afloat(3,6), both of which are largely unknown. Here we show-using observations from a hot-water-drilled access hole-that the grounding zone of Thwaites Eastern Ice Shelf (TEIS) is characterized by a warm and highly stable water column with temperatures substantially higher than the in situ freezing point. Despite these warm conditions, low current speeds and strong density stratification in the ice-ocean boundary layer actively restrict the vertical mixing of heat towards the ice base(7,8), resulting in strongly suppressed basal melting. Our results demonstrate that the canonical model of ice-shelf basal melting used to generate sea-level projections cannot reproduce observed melt rates beneath this critically important glacier, and that rapid and possibly unstable grounding-line retreat may be associated with relatively modest basal melt rates.
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| 2. |
- Frutkin, Andrew D., et al.
(author)
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A critical developmental role for tgfbr2 in myogenic cell lineages is revealed in mice expressing SM22-Cre, not SMMHC-Cre
- 2006
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In: Journal of Molecular and Cellular Cardiology. - : Elsevier BV. - 1095-8584 .- 0022-2828. ; 41:4, s. 724-731
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Journal article (peer-reviewed)abstract
- Smooth muscle cell (SMC)-specific deletion of transforming growth factor beta (TGF-beta) signaling would help elucidate the mechanisms through which TGF-beta signaling contributes to vascular development and disease. We attempted to generate mice with SMC-specific deletion of TGF-beta signaling by mating mice with a conditional ("floxed") allele for the type 11 TGF-beta receptor (tgfbr2(flox)) to mice with SMC-targeted expression of Cre recombinase. We bred male mice transgenic for smooth muscle myosin heavy chain (SMMHC)-Cre with females carrying tgfbr2(flox). Surprisingly, SMMHC-Cre rnice recombined tglbr2(flox) at low levels in SMC and at high levels in the testis. Recombination of tgfbr2(flox) in testis correlated with high-level expression of SMMHC-Cre in testis and germline transmission of tgfbr2(null). In contrast, mice expressing Cre from a SM22 alpha promoter (SM22-Cre) efficiently recombined tgfbr2(flox) in vascular and visceral SMC and the heart, but not in testis. Use of the R26R reporter allele confirmed that Cre-mediated recombination in vascular SMC was inefficient for SMMHC-Cre mice and highly efficient for SM22-Cre mice. Breedings that introduced the SM22-Cre allele into tgfbr2(flox) zygotes in order to generate adult mice that are hemizygous for SM22-Cre and homozygous for tgfbr2(flox) and would have conversion of tgfbr2(flox/flox) to tgfbr2(null/null) in SMC-produced no live SM22-Cre : tgfbr2(flox/flox) pups (P < 0.001). We conclude: (1) "SMC-targeted" Cre lines vary significantly in specificity and efficiency of Cre expression; (2) TGF-beta signaling in the subset of cells that express SM22 alpha is required for normal development; (3) generation of adult mice with absent TGF-beta signaling in SMC remains a challenge. (c) 2006 Elsevier Inc. All rights reserved.
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