Antarctic ice-sheet sensitivity to obliquity forcing enhanced through ocean connections

Deep sea geological records indicate that Antarctic ice-sheet growth and decay is strongly influenced by the Earth's astronomical variations (known as Milankovitch cycles), and that the frequency of the glacial-interglacial cycles changes through time. Here we examine the emergence of a strong obliquity (axial tilt) control on Antarctic ice-sheet evolution during the Miocene by correlating the Antarctic margin geological records from 34 to 5 million years ago with a measure of obliquity sensitivity that compares the variance in deep sea sediment core oxygen-isotope data at obliquity timescales with variance of the calculated obliquity forcing. Our analysis reveals distinct phases of ice-sheet evolution and suggests the sensitivity to obliquity forcing increases when ice-sheet margins extend into marine environments. We propose that this occurs because obliquity-driven changes in the meridional temperature gradient affect the position and strength of the circum-Antarctic easterly flow and enhance (or reduce) ocean heat transport across the Antarctic continental margin. The influence of obliquity-driven changes in ocean dynamics is amplified when marine ice sheets are extensive, and sea ice is limited. Our reconstruction of the Antarctic ice-sheet history suggests that if sea-ice cover decreases in the coming decades, ocean-driven melting at the ice-sheet margin will be amplified.Published132-1371A. Geomagnetismo e Paleomagnetismo4A. Oceanografia e clima5A. Ricerche polari e paleoclimaJCR Journa

Global Tipping Points Report 2023: Ch1.2: Cryosphere tipping points.

Drastic changes in our planet’s frozen landscapes have occurred over recent decades, from Arctic sea ice decline and thawing of permafrost soils to polar amplification, the retreat of glaciers and ice loss from the ice sheets. In this chapter, we assess multiple lines of evidence for tipping points in the cryosphere – encompassing the ice sheets on Greenland and Antarctica, sea ice, mountain glaciers and permafrost – based on recent observations, palaeorecords, numerical modelling and theoretical understanding. With about 1.2°C of global warming compared to pre-industrial levels, we are getting dangerously close to the temperature thresholds of some major tipping points for the ice sheets of Greenland and West Antarctica. Crossing these would lock in unavoidable long-term global sea level rise of up to 10 metres. There is evidence for localised and regional tipping points for glaciers and permafrost and, while evidence for global-scale tipping dynamics in sea ice, glaciers and permafrost is limited, their decline will continue with unabated global warming. Because of the long response times of these systems, some impacts of crossing potential tipping points will unfold over centuries to millennia. However, with the current trajectory of greenhouse gas (GHG) emissions and subsequent anthropogenic climate change, such largely irreversible changes might already have been triggered. These will cause far-reaching impacts for ecosystems and humans alike, threatening the livelihoods of millions of people, and will become more severe the further global warming progresses

Identification of Novel Targets of CSL-Dependent Notch Signaling in Hematopoiesis

Somatic activating mutations in the Notch1 receptor result in the overexpression of activated Notch1, which can be tumorigenic. The goal of this study is to understand the molecular mechanisms underlying the phenotypic changes caused by the overexpression of ligand independent Notch 1 by using a tetracycline inducible promoter in an in vitro embryonic stem (ES) cells/OP9 stromal cells coculture system, recapitulating normal hematopoiesis. First, an in silico analysis of the promoters of Notch regulated genes (previously determined by microarray analysis) revealed that the motifs recognized by regulatory proteins known to mediate hematopoiesis were overrepresented. Notch 1 does not bind DNA but instead binds the CSL transcription factor to regulate gene expression. The in silico analysis also showed that there were putative CSL binding sites observed in the promoters of 28 out of 148 genes. A custom ChIP-chip array was used to assess the occupancy of CSL in the promoter regions of the Notch1 regulated genes in vivo and showed that 61 genes were bound by activated Notch responsive CSL. Then, comprehensive mapping of the CSL binding sites genome-wide using ChIP-seq analysis revealed that over 10,000 genes were bound within 10 kb of the TSS (transcription start site). The majority of the targets discovered by ChIP-seq belong to pathways that have been shown by others to crosstalk with Notch signaling. Finally, 83 miRNAs were significantly differentially expressed by greater than 1.5-fold during the course of in vitro hematopoiesis. Thirty one miRNA were up-regulated and fifty two were down-regulated. Overexpression of Notch1 altered this pattern of expression of microRNA: six miRNAs were up-regulated and four were down regulated as a result of activated Notch1 overexpression during the course of hematopoiesis. Time course analysis of hematopoietic development revealed that cells with Notch 1 overexpression mimic miRNA expression of cells in a less mature stage, which is consistent with our previous biological characterization

Behavioural tendencies of the last British-Irish Ice Sheet revealed by data-model comparison

Integrating ice sheet models with empirical data pertaining to palaeo-ice sheets promotes advances in the models used in sea-level predictions, and can improve our understanding of past ice sheet behaviour. The large number of empirical constraints on last British-Irish Ice Sheet make it ideal for model-data comparison experiments. Here, we present an ensemble of 600 model simulations, which are compared to data on former ice flow extent, flow geometry and deglaciation timing. Simulations which poorly recreate data were ruled out, allowing us to examine the remaining physically realistic simulations which capture the ice sheets’ behavioural tendencies. Our results led to a novel reconstruction of behaviour in the data poor region of the North Sea, insights into ice stream, potential ice shelf, and readvance dynamics, and potential locations of periphery ice caps. We also propose that the asynchronous behaviour of the British-Irish Ice Sheet is a consequence of the geography of the British Isles and the merging and splitting of different bodies of ice through saddle merger and collapse. Furthermore, persistent model-data mismatches highlight the need for model development, especially regarding the physics of ice-ocean interactions. Thus, this work highlights the power of integrating models and data, a long-held aim of palaeoglaciolog

Kaivoskoneiden ohjauskonsolin ja penkkien nostoapuvälineen suunnittelu

Tämän työn tarkoituksena oli suunnitella nostoapuväline helpottamaan Normetin Iisalmen-yksikön ohjaamoiden esivarustelusolussa tapahtuvaa ohjauskonsoleiden ja penkkien asennusta sekä parantamaan työergonomiaa. Työn tavoitteena oli suunnitella mahdollisimman edullinen ja toimiva alle 1000 euron nostoapuväline, joka voidaan CE-merkitä. Tarkoituksena oli tehdä 3D-mallit ja valmistuspiirustukset, jotka työn valmistumisen jälkeen luovutettaisiin Normetille. Työn alussa esiteltiin tuotekehitysprosessin vaiheet ja mitä ne sisältävät, CE-merkintä ja mitä sen saaminen edellyttää sekä nostoapuvälineet ja mitä ne ovat. Tämän jälkeen siirryttiin suunnitteluvaiheeseen, jossa käytiin lävitse luonnosteluvaihetta, itse suunnittelua ja aikaan saatua nostoapuvälinettä sekä FE-analyysiä. Tuloksina saatiin 3D-malli ja valmistuspiirustukset, joiden pohjalta nostoapuväline voidaan valmistaa. Onnistuneesta FE-analyysistä pystyttiin näkemään, missä kohdassa nostoapuvälinettä ovat suurimmat jännityskeskittymät ja toteamaan, että tuotteen rakenne kestää kuorman, joka se on suunniteltu nostamaan. Rakenne kesti jopa kolminkertaisen kuorman nostamisen ilman hajoamista. Hinta-arvio oli erittäin karkea, siinä listatut komponentit ja materiaalit pystyvät vielä muuttumaan sekä niiden hinta vaihdella. Arvion pohjalta voitiin kuitenkin todeta, että tuotteen valmistushinta ilman ruuvitarraimia mitä todennäköisimmin jäi alle 1000 euron, mutta ruuvitarraimien kanssa nostoapuvälineen hinta lähes kaksinkertaistui

The DeepMIP contribution to PMIP4:experimental design for model simulations of the EECO, PETM, and pre-PETM (version 1.0)

Past warm periods provide an opportunity to evaluate climate models under extreme forcing scenarios, in particular high (&gt; 800ppmv) atmospheric CO2 concentrations. Although a post hoc intercomparison of Eocene (∼ 50 Ma) climate model simulations and geological data has been carried out previously, models of past high-CO2 periods have never been evaluated in a consistent framework. Here, we present an experimental design for climate model simulations of three warm periods within the early Eocene and the latest Paleocene (the EECO, PETM, and pre-PETM). Together with the CMIP6 pre-industrial control and abrupt 4 × CO2 simulations, and additional sensitivity studies, these form the first phase of DeepMIP-the Deep-time Model Intercomparison Project, itself a group within the wider Paleoclimate Modelling Intercomparison Project (PMIP). The experimental design specifies and provides guidance on boundary conditions associated with palaeogeography, greenhouse gases, astronomical configuration, solar constant, land surface processes, and aerosols. Initial conditions, simulation length, and output variables are also specified. Finally, we explain how the geological data sets, which will be used to evaluate the simulations, will be developed.</p