Planetary polar explorer – the case for a next-generation remote sensing mission to low Mars orbit

We propose the exploration of polar areas on Mars by a next-generation orbiter mission. In particular, we aim at studying the seasonal and regional variations in snow-deposits, which – in combination with measurements of temporal variations in rotation and gravity field – will improve models of the global planetary CO2 cycle. A monitoring of polar scarps for rock falls and avalanche events may provide insights into the dynamics of ice sheets. The mapping of the complex layering of polar deposits, believed to contain an important record of climate history, may help us understand the early climate collapse on the planet. Hence, we propose an innovative next-generation exploration mission in polar circular Low Mars Orbit, which will be of interest to scientists and challenging to engineers alike. Schemes will be developed to overcome atmosphere drag forces acting upon the spacecraft by an electric propulsion system. Based on the experience of missions of similar type in Earth orbit we believe that a two-year mission in circular orbit is possible at altitudes as low as 150 km. Such a mission opens new opportunities for novel remote sensing approaches, not requiring excessive telescope equipment or power. We anticipate precision altimetry, powerful radars, high-resolution imaging, and magnetic field mapping.

The interaction of climate history and evolution impacts alpine biodiversity assembly differently in freshwater and on land

Quaternary climate fluctuations can affect biodiversity assembly through speciation in two non-mutually-exclusive ways: a glacial species pump, where isolation in glacial refugia accelerates allopatric speciation, and adaptive radiation during ice-free periods. Here we detected biogeographic and genetic signatures associated with both mechanisms in the generation of the European Alps biodiversity. Age distributions of endemic and widespread species within aquatic and terrestrial taxa (amphipods, fishes, amphibians, butterflies and flowering plants) revealed that endemic fish evolved only in lakes, are highly sympatric and mainly of Holocene age, consistent with adaptive radiation. Endemic amphipods are ancient, suggesting preglacial radiation with limited range expansion and local Pleistocene survival, perhaps facilitated by a groundwater-dwelling lifestyle. Terrestrial endemics are mostly of Pleistocene age, and are thus more consistent with the glacial species pump. The lack of evidence for Holocene adaptive radiation in the terrestrial biome may be attributable to a faster range expansion of these taxa after glacial retreats, though fewer stable environments may also have contributed to differences between terrestrial areas and lakes. The high proportion of young, endemic species make the Alps vulnerable to climate change, but the mechanisms and consequences of species loss will likely differ between biomes because of their distinct histories.

Using Pollen Records from New Zealand and Southern Chile to Reconstruct New Zealand Climate Variability over the Last 14,000 years

<p>Climate variability in New Zealand (34-47°S), a long, narrow continental strip straddling the mid-latitudes of the Southern Hemisphere, results largely from the interplay between sub-tropical and sub-Antarctic atmospheric and oceanic circulation systems. Despite their importance to present-day New Zealand climate, these hemispheric-wide systems have only recently come under the spotlight of paleo-climate investigations with most attention having traditionally been centred on reconstructing climate trends. This PhD adopts a broader approach to climate reconstruction, by developing and comparing two new pollen-climate reconstructions from New Zealand (38-42°S) and one from Patagonia, Southern Chile (43°S). At each site, paleo-climate interpretations are based on the changes in climate-sensitive plant indicators. The influence of hemispheric atmospheric circulation on New Zealand climate history is assessed by: (1) comparing New Zealand climate/vegetation trends with published proxies from low- and high-latitudes, and (2) comparing New Zealand reconstructions with the Patagonian record. Finally, a multi-millennial pattern of Southern Hemisphere circulation over the last 14,000 cal yr BP (calendar years before AD 1950) is outlined. The first record presented is a 16,000-year temperature reconstruction from a small alpine lake in South Island, New Zealand (41°S), based on pollen and plant macrofossils. Climate variations are interpreted from the relative abundance of lowland and highland vegetation. The results include a lifting of the altitudinal forest limits attributed to warming pulses between 13,000-10,000 cal yr BP and between 7000-6000 cal yr BP, and a decline of lowland relative to upland forest taxa interpreted as cooling trends between 10,000-7000 cal yr BP and over the last 3000 years. The second record gives 15,000-year temperature and precipitation reconstructions from a peatbog in northern New Zealand (38°S), based on pollen and charcoal analysis. Temperature changes are assessed based on two quantitate reconstructions, whereas precipitation trends are inferred from variations in arboreal taxa with different drought tolerances. A long-term warming is inferred between 14,600-10,000 cal yr BP. Persistent dry conditions are recorded between 12,000-10,000 cal yr BP, followed by a long-term wet period between 10,000-6000 cal yr BP. The last 7000 years feature a long-term drying trend that culminates with persistent drier conditions over the last 3000 years. The third record provides a 16,000-year reconstruction from a small lake in Northwestern Patagonia (43°S), based on pollen and charcoal analysis. Climate conditions are inferred from the relative variations of pollen types with distinctive climate tolerances and complemented with changes in fire activity. These variations are in turn interpreted as resulting from changes in the position and/or strength of the Southern Westerly Winds (SWW). Cold and moist conditions attributable to stronger/northward-shifted SWW winds are observed between 16,000-13,600 cal yr BP. In contrast, warm and dry conditions suggestive of weaker/southward-shifted SWW are detected between 12,000-10,000 cal yr BP. The last 6000 years shows a trend towards colder conditions and increasing precipitation variability, suggesting a highly variable westerly flow over Patagonia. A comparison between the New Zealand and the Patagonia records suggest: (1) weakened/southward-shifted westerly flow over the southern mid-latitudes between 13,000-10,000 cal yr BP caused rapid warming and peak temperatures in New Zealand, as well as dry conditions in Northern New Zealand, (2) Enhanced/northward-shifted SWW over the southern mid-latitudes between 9000-4000 cal yr BP caused decreasing temperatures in the South Island and increasing precipitation in Northern New Zealand and (3) Overall weakened/southward-shifted SWW after 4000 cal yr BP caused a decrease in temperature in the southern New Zealand site. Drier conditions in Northern New Zealand and the overall increase in climate instability at all sites may have resulted from more frequent El Niño events along with an increase in sub-tropical climate variability.</p>

Using Pollen Records from New Zealand and Southern Chile to Reconstruct New Zealand Climate Variability over the Last 14,000 years

<p>Climate variability in New Zealand (34-47°S), a long, narrow continental strip straddling the mid-latitudes of the Southern Hemisphere, results largely from the interplay between sub-tropical and sub-Antarctic atmospheric and oceanic circulation systems. Despite their importance to present-day New Zealand climate, these hemispheric-wide systems have only recently come under the spotlight of paleo-climate investigations with most attention having traditionally been centred on reconstructing climate trends. This PhD adopts a broader approach to climate reconstruction, by developing and comparing two new pollen-climate reconstructions from New Zealand (38-42°S) and one from Patagonia, Southern Chile (43°S). At each site, paleo-climate interpretations are based on the changes in climate-sensitive plant indicators. The influence of hemispheric atmospheric circulation on New Zealand climate history is assessed by: (1) comparing New Zealand climate/vegetation trends with published proxies from low- and high-latitudes, and (2) comparing New Zealand reconstructions with the Patagonian record. Finally, a multi-millennial pattern of Southern Hemisphere circulation over the last 14,000 cal yr BP (calendar years before AD 1950) is outlined. The first record presented is a 16,000-year temperature reconstruction from a small alpine lake in South Island, New Zealand (41°S), based on pollen and plant macrofossils. Climate variations are interpreted from the relative abundance of lowland and highland vegetation. The results include a lifting of the altitudinal forest limits attributed to warming pulses between 13,000-10,000 cal yr BP and between 7000-6000 cal yr BP, and a decline of lowland relative to upland forest taxa interpreted as cooling trends between 10,000-7000 cal yr BP and over the last 3000 years. The second record gives 15,000-year temperature and precipitation reconstructions from a peatbog in northern New Zealand (38°S), based on pollen and charcoal analysis. Temperature changes are assessed based on two quantitate reconstructions, whereas precipitation trends are inferred from variations in arboreal taxa with different drought tolerances. A long-term warming is inferred between 14,600-10,000 cal yr BP. Persistent dry conditions are recorded between 12,000-10,000 cal yr BP, followed by a long-term wet period between 10,000-6000 cal yr BP. The last 7000 years feature a long-term drying trend that culminates with persistent drier conditions over the last 3000 years. The third record provides a 16,000-year reconstruction from a small lake in Northwestern Patagonia (43°S), based on pollen and charcoal analysis. Climate conditions are inferred from the relative variations of pollen types with distinctive climate tolerances and complemented with changes in fire activity. These variations are in turn interpreted as resulting from changes in the position and/or strength of the Southern Westerly Winds (SWW). Cold and moist conditions attributable to stronger/northward-shifted SWW winds are observed between 16,000-13,600 cal yr BP. In contrast, warm and dry conditions suggestive of weaker/southward-shifted SWW are detected between 12,000-10,000 cal yr BP. The last 6000 years shows a trend towards colder conditions and increasing precipitation variability, suggesting a highly variable westerly flow over Patagonia. A comparison between the New Zealand and the Patagonia records suggest: (1) weakened/southward-shifted westerly flow over the southern mid-latitudes between 13,000-10,000 cal yr BP caused rapid warming and peak temperatures in New Zealand, as well as dry conditions in Northern New Zealand, (2) Enhanced/northward-shifted SWW over the southern mid-latitudes between 9000-4000 cal yr BP caused decreasing temperatures in the South Island and increasing precipitation in Northern New Zealand and (3) Overall weakened/southward-shifted SWW after 4000 cal yr BP caused a decrease in temperature in the southern New Zealand site. Drier conditions in Northern New Zealand and the overall increase in climate instability at all sites may have resulted from more frequent El Niño events along with an increase in sub-tropical climate variability.</p>

Genome of the estuarine oyster provides insights into climate impact and adaptive plasticity

Understanding the roles of genetic divergence and phenotypic plasticity in adaptation is central to evolutionary biology and important for assessing adaptive potential of species under climate change. Analysis of a chromosome-level assembly and resequencing of individuals across wide latitude distribution in the estuarine oyster (Crassostrea ariakensis) revealed unexpectedly low genomic diversity and population structures shaped by historical glaciation, geological events and oceanographic forces. Strong selection signals were detected in genes responding to temperature and salinity stress, especially of the expanded solute carrier families, highlighting the importance of gene expansion in environmental adaptation. Genes exhibiting high plasticity showed strong selection in upstream regulatory regions that modulate transcription, indicating selection favoring plasticity. Our findings suggest that genomic variation and population structure in marine bivalves are heavily influenced by climate history and physical forces, and gene expansion and selection may enhance phenotypic plasticity that is critical for the adaptation to rapidly changing environments.

An Oceanographic Study of the Cavity Beneath the McMurdo Ice Shelf, Antarctica

<p><b>This thesis reports the first observations of currents, temperature and salinity beneaththe McMurdo Ice Shelf, Antarctica. They are reviewed and discussed here in conjunctionwith results of a numerical modelling study used to simulate current flow and to investigatelocal sediment deposition. The McMurdo Ice Shelf lies behind Ross Island off theVictoria Land coast of Antarctica, and represents the northwest corner of the much largerRoss Ice Shelf. The site will be drilled by the ANDRILL consortium in 2006, passingthrough the ice shelf, the water column, and 1000 m into the sea floor, to obtain a recordof ice shelf and climate history in this area.</b></p> <p>This study stems from a site survey carried out in early 2003, for which access holeswere melted at two locations on the McMurdo Ice Shelf. Current meters surveyed multipledepths simultaneously during spring tides, and profiles of temperature and salinitywere collected through a diurnal tidal cycle at each site. Maximum currents were recordedin the boundary layer at the base of the ice shelf, reaching 0.22 m s−1 during the flood tide.</p> <p>The salinity and temperature profiles were similar at the two sites, with greater temporalvariability observed at the site closer to the open water of McMurdo Sound. Supercooling,due to the pressure-dependence of the in-situ freezing temperature, was observed at oneof the sites. At the second site, where the draft of the ice shelf was deeper, temperaturescorresponding to basal melting were observed.</p> <p>At a third site on the sea ice at the northwestern edge of the McMurdo Ice Shelf, acurrent meter surveyed the water column to 320 metres below sea level for 23 days. Thisallowed comparison of current behaviour through spring and neap tides, and between subseaice and sub-ice shelf environments in the same season. Net throughflow over springtides at each of the three sites was consistent with transport eastwards from McMurdoSound along the channel defined by local bathymetry. Profiles of temperature and salinityfrom beneath the ice shelf were likewise consistent with McMurdo Sound being the sourceof the observed water masses.</p> <p>Flow along the sub-ice shelf channel was further investigated using an adaptation of atwo-dimensional thermohaline ocean model. Year-long profiles of temperature and salinityfrom southern McMurdo Sound were used to seasonally force the model, resulting in annual variation in all parameters. The rate of melting decreased monotonically from∼0.6 m yr−1 at the deep end of the ice shelf, into a region of freezing associated withsupercooling closer to the McMurdo Sound end of the domain. This change in regimemirrored the observations from the boundary layer beneath the McMurdo Ice Shelf.</p> <p>Sediment transport and deposition were investigated, with settling velocities used to representsediment sizes ranging from biogenic pellets and fine sand through algal flocs to finemud, particle types known and described from the present day environment. This methodof incorporating sedimentation processes gave results similar to observations from surfacesediment cores collected beneath the ice shelf. The larger grains were preferentially depositedclose to the open water McMurdo Sound source, whereas fine-grained materialwas entrained into the general circulation and deposited by regions of down-welling. Asettling velocity of ∼1x10−4 m s−1, corresponding to a grain size of ∼5 μm, defined theboundary between these depositional behaviours.</p> <p>Characteristics of the water beneath the ice shelf suggest that it had been transportedfrom McMurdo Sound, being modified through interaction with the base of the ice shelf.</p> <p>This pattern of throughflow was also seen in the current meter data, with a strong tidalsignal throughout the water column superimposed on the net transport eastward fromMcMurdo Sound and under the ice shelf. This net flow pattern was supported by theresults of the longer-term simulation experiments.</p>

An Oceanographic Study of the Cavity Beneath the McMurdo Ice Shelf, Antarctica

<p><b>This thesis reports the first observations of currents, temperature and salinity beneaththe McMurdo Ice Shelf, Antarctica. They are reviewed and discussed here in conjunctionwith results of a numerical modelling study used to simulate current flow and to investigatelocal sediment deposition. The McMurdo Ice Shelf lies behind Ross Island off theVictoria Land coast of Antarctica, and represents the northwest corner of the much largerRoss Ice Shelf. The site will be drilled by the ANDRILL consortium in 2006, passingthrough the ice shelf, the water column, and 1000 m into the sea floor, to obtain a recordof ice shelf and climate history in this area.</b></p> <p>This study stems from a site survey carried out in early 2003, for which access holeswere melted at two locations on the McMurdo Ice Shelf. Current meters surveyed multipledepths simultaneously during spring tides, and profiles of temperature and salinitywere collected through a diurnal tidal cycle at each site. Maximum currents were recordedin the boundary layer at the base of the ice shelf, reaching 0.22 m s−1 during the flood tide.</p> <p>The salinity and temperature profiles were similar at the two sites, with greater temporalvariability observed at the site closer to the open water of McMurdo Sound. Supercooling,due to the pressure-dependence of the in-situ freezing temperature, was observed at oneof the sites. At the second site, where the draft of the ice shelf was deeper, temperaturescorresponding to basal melting were observed.</p> <p>At a third site on the sea ice at the northwestern edge of the McMurdo Ice Shelf, acurrent meter surveyed the water column to 320 metres below sea level for 23 days. Thisallowed comparison of current behaviour through spring and neap tides, and between subseaice and sub-ice shelf environments in the same season. Net throughflow over springtides at each of the three sites was consistent with transport eastwards from McMurdoSound along the channel defined by local bathymetry. Profiles of temperature and salinityfrom beneath the ice shelf were likewise consistent with McMurdo Sound being the sourceof the observed water masses.</p> <p>Flow along the sub-ice shelf channel was further investigated using an adaptation of atwo-dimensional thermohaline ocean model. Year-long profiles of temperature and salinityfrom southern McMurdo Sound were used to seasonally force the model, resulting in annual variation in all parameters. The rate of melting decreased monotonically from∼0.6 m yr−1 at the deep end of the ice shelf, into a region of freezing associated withsupercooling closer to the McMurdo Sound end of the domain. This change in regimemirrored the observations from the boundary layer beneath the McMurdo Ice Shelf.</p> <p>Sediment transport and deposition were investigated, with settling velocities used to representsediment sizes ranging from biogenic pellets and fine sand through algal flocs to finemud, particle types known and described from the present day environment. This methodof incorporating sedimentation processes gave results similar to observations from surfacesediment cores collected beneath the ice shelf. The larger grains were preferentially depositedclose to the open water McMurdo Sound source, whereas fine-grained materialwas entrained into the general circulation and deposited by regions of down-welling. Asettling velocity of ∼1x10−4 m s−1, corresponding to a grain size of ∼5 μm, defined theboundary between these depositional behaviours.</p> <p>Characteristics of the water beneath the ice shelf suggest that it had been transportedfrom McMurdo Sound, being modified through interaction with the base of the ice shelf.</p> <p>This pattern of throughflow was also seen in the current meter data, with a strong tidalsignal throughout the water column superimposed on the net transport eastward fromMcMurdo Sound and under the ice shelf. This net flow pattern was supported by theresults of the longer-term simulation experiments.</p>

The Mittimatalik Siku Asijjipallianinga (Sea Ice Climate Atlas): How Inuit Knowledge, Earth Observations, and Sea Ice Charts Can Fill IPCC Climate Knowledge Gaps

The IPCC special report on the ocean and cryosphere in a changing climate (SROCC) highlights with high confidence that declining Arctic sea ice extents and increased ship-based transportation are impacting the livelihoods of Arctic Indigenous peoples. Current IPCC assessments cannot address the local scale impacts and adaptive needs of Arctic Indigenous communities based on the global, top-down model approaches used. Inuit maintain the longest unrecorded climate history of sea ice in Canada, and to support Inuit community needs, a decolonized, Inuit knowledge-based approach was co-developed in the community of Mittimatalik, Nunavut (Canada) to create the Mittimatalik siku asijjipallianinga (sea ice climate atlas) 1997–2019. This paper presents the novel approach used to develop the atlas based on Inuit knowledge, earth observations and Canadian Ice Service (CIS) sea ice charts, and demonstrates its application. The atlas provides an adaptation tool that Mittimatalik can use to share locations of known and changing sea ice conditions to plan for safe sea ice travel. These maps can also be used to support the safety and situational awareness of territorial and national search and rescue partners, often coming from outside the region and having limited knowledge of local sea ice conditions. The atlas demonstrates the scientific merit of Inuit knowledge in environmental assessments for negotiating a proposal to extend the shipping seasons for the nearby Mary River Mine. The timing and rates of sea ice freeze-up (October–December) in Mittimatalik are highly variable. There were no significant trends to indicate that sea ice is freezing up later to support increased shipping opportunities into the fall. The atlas shows that the first 2 weeks of November are critical for landfast ice formation, and icebreaking at this time would compromise the integrity of the sea ice for safe travel, wildlife migration and reproduction into the winter months. There was evidence that sea ice break-up (May–July) and the fracturing of the nearby floe edge have been occurring earlier in the last 10 years (2010–2019). Shipping earlier into the break-up season could accelerate the break-up of an already declining sea ice travel season, that Inuit are struggling to maintain.