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During austral summer (DJF) 2017/18, the New Zealand region experienced an unprecedented coupled ocean-atmosphere heatwave, covering an area of 4 million km². Regional average air temperature anomalies over land were +2.2 °C, and sea surface temperature anomalies reached +3.7 °C in the eastern Tasman Sea. This paper discusses the event, including atmospheric and oceanic drivers, the role of anthropogenic warming, and terrestrial and marine impacts. The heatwave was associated with very low wind speeds, reducing upper ocean mixing and allowing heat fluxes from the atmosphere to the ocean to cause substantial warming of the stratified surface layers of the Tasman Sea. The event persisted for the entire austral summer resulting in a 3.8 ± 0.6 km³ loss of glacier ice in the Southern Alps (the largest annual loss in records back to 1962), very early Sauvignon Blanc wine-grape maturation in Marlborough, and major species disruption in marine ecosystems. The dominant driver was positive Southern Annular Mode (SAM) conditions, with a smaller contribution from La Niña. The long-term trend towards positive SAM conditions, a result of stratospheric ozone depletion and greenhouse gas increase, is thought to have contributed through association with more frequent anticyclonic 'blocking' conditions in the New Zealand region and a more poleward average latitude for the Southern Ocean storm track. The unprecedented heatwave provides a good analogue for possible mean conditions in the late 21st century. The best match suggests this extreme summer may be typical of average New Zealand summer climate for 2081-2100, under the RCP4.5 or RCP6.0 scenario.

Marine heatwaves pose an increasing threat to the ocean’s wellbeing as global warming progresses. Forecasting marine heatwaves is challenging due to the various factors that affect their occurrence, including large variability in the atmospheric state. In this study we demonstrate a causal link between ocean heat content and the area and intensity of marine heatwaves in the Tasman Sea on interannual to decadal time scales. Ocean heat content variations are more persistent than ‘weather-related’ atmospheric drivers (e.g. blocking high pressure systems) for marine heatwaves and thus provide better predictive skill on timescales longer than weeks. Using data from a forced global ocean sea-ice model, we show that ocean heat content fluctuations in the Tasman Sea are predominantly controlled by oceanic meridional heat transport from the subtropics, which in turn, is mainly characterized by the interplay of the East Australian Current and the Tasman Front. Variability in these currents is impacted by wind stress curl anomalies north of this region, following Sverdrup´s and Godfrey’s ‘Island Rule’ theories. Data from models and observations show that periods with positive upper (2000m) ocean heat content anomalies or rapid increases in ocean heat content are characterized by more frequent, larger, longer and more intense marine heatwaves on interannual to decadal timescales. Thus, the oceanic heat content in the Tasman Sea acts as a preconditioner and has a prolonged predictive skill compared to the atmospheric state (e.g. surface heat fluxes), making ocean heat content a useful indicator and measure of the likelihood of marine heatwaves.

During austral summers (DJF) 1934/35, 2017/18 and 2018/19, the New Zealand (NZ) region (approximately 4 million km2) experienced the most intense coupled ocean-atmosphere heatwaves on record. Average air temperature anomalies over land were + 1.7 to 2.1 °C while sea surface temperatures (SST) were 1.2 to 1.9 °C above average. All three heatwaves exhibited maximum SST anomalies west of the South Island of NZ. Atmospheric circulation anomalies showed a pattern of blocking centred over the Tasman Sea extending south-east of NZ, accompanied by strongly positive Southern Annular Mode conditions, and reduced trough activity over NZ. Rapid melt of seasonal snow occurred in all three cases. For the two most recent events, combined ice loss in the Southern Alps was estimated at 8.9 km3 (22% of the 2017 volume). Sauvignon blanc and Pinot noir wine grapes had above average berry number and bunch mass in 2018 but were below average in 2019. Summerfruit harvest (cherries and apricots) was 14 and 2 days ahead of normal in 2017/18 and 2018/19 respectively. Spring wheat simulations suggested earlier flowering and lower grain yields compared to average, and below-average yield and tuber quality in potatoes crops occurred. Major species disruption occurred in marine ecosystems. Hindcasts indicate that the heatwaves were either atmospherically driven or arose from combinations of atmospheric surface warming and oceanic heat advection.

This paper describes the development of New Zealand's Earth System Model (NZESM) and evaluates its performance against its parent model (United Kingdom Earth System Model, UKESM) and observations. The main difference between the two earth system models is an embedded high‐resolution (1/5°) nested region over the oceans around New Zealand in the NZESM. Due to this finer ocean model mesh, currents such as the East Australian Current, East Australian Current Extension, Tasman Front, and Tasman Leakage, and their volume and heat transports are better simulated in the NZESM. The improved oceanic transports have led to a reduction in upper ocean temperature and salinity biases over the nested region. In addition, net transports through the Tasman Sea of volume, heat and salt in the NZESM agree better with previously reported estimates. A consequence of the increased cross‐Tasman Sea transports in the NZESM is increased temperatures and salinity west of Australia and in the Southern Ocean reducing the meridional sea surface temperature gradient between the subtropics and sub‐Antarctic. This also leads to a weakening of the westerly winds between 60°S and 45°S over large parts of the Southern Ocean, which reduces the northward Ekman transport, reduces the formation of Antarctic Intermediate Water, and allows for a southward expansion of the Super‐Gyre in all ocean basins. Connecting an improved oceanic circulation around New Zealand to a basin‐wide Super‐Gyre response is an important step forward in our current understanding of how local scales can influence global scales in a fully coupled earth system model. Plain Language Summary We describe the model development of the New Zealand Earth System Model and assess its performance against the model on which it is based (United Kingdom Earth System Model) and observations. The New Zealand Earth System Model is a fully coupled earth system model, which aims to model all relevant bio‐physical processes in and between the atmosphere, land, ocean, and sea‐ice. The main difference between both models is that the oceans around New Zealand in the New Zealand Earth System Model are more precisely modeled, due to a refined ocean model mesh in this region. That results in a more accurate oceanic circulation around New Zealand in the New Zealand Earth System Model compared to the United Kingdom Earth System Model and reduced model biases of temperature and salinity. These oceanic changes have implications beyond the oceans around New Zealand, causing a warming in the Southern Ocean and a related weakening of the westerly winds over the Southern Ocean. This weakening of the winds allows subtropical waters to reach further south into the Southern Ocean. It is notable that regional changes in the ocean circulation can have implications on the global scale. Key Points NZESM is a nested fully coupled ESM based on UKESM with a high‐resolution ocean grid of 1/5° around New Zealand The oceanic circulation is improved in NZESM over the nested domain and model biases of temperature and salinity are reduced The Super‐Gyre intensifies and expands southward due to wind changes triggered by changes in the large‐scale heat transport

During austral warm seasons (November - March, NDJFM) of 1934/35, 2017/18, 2018/19 and 2021/22 the New Zealand (NZ) region experienced the most intense coupled ocean/atmosphere (MHW/AHW) heatwaves on record. Average temperature anomalies over land and sea were +1.2 to 1.4°C above average. Common to all four events were maximum sea surface temperature (SST) anomalies to the west of the South Island of NZ. Atmospheric circulation anomalies showed a pattern of blocking high pressure over the Tasman Sea and Pacific Ocean to the south, and southeast of NZ, and reduced trough activity over and to the east of NZ, accompanied by strongly positive Southern Annular Mode conditions. Hindcasts for 2017/18, 2018/19 and 2021/22 NDJFM indicate that positive temperature anomalies around 1°C occurred in the Tasman Sea, and near 1.5°C for the Chatham Rise. The temperature anomalies in the upper 50m of the ocean are consistent with the 500hPa atmospheric height anomalies. The temperature anomalies in the upper 50m of the ocean are consistent with the 500hPa atmospheric height anomalies and associated winds. The eastern Tasman Sea during August 2021 to July 2022 experienced the highest annual number of MHW days during the satellite-era (1981-present) from OISSTv2.1 data. Under 1.5°C of global warming the four events would have ERIs of 2-3 years, and with 2°C of warming all would be considered cool years relative to the +2°C climate. For the 1957-2022 period, the two most intense heatwaves have ERIs of between 30 to 150 years. Major loss of glacial ice occurred from Southern Alps glaciers with rapid melt of seasonal snow in all cases. Slow advances in grape phenology since 1948 may be associated with increases in temperature over the same period. Cherries and apricot harvest dates advanced by one to two weeks. Marine impacts may be linked to starvation of kororā/Little Penguin (Eudyptula minor) chicks in the Bay of Plenty. Chicks weighed less and had a lower body condition score in 2020 and 2021 compared to 2019 and rescue calls in 2021 reached the highest volumes since 2015. The first record of warm-water prey species in the diet of yellow-eyed penguins at Moeraki occurred, as well as widespread sea-sponge bleaching around northern and southern NZ.

High-density regions within the spiral arms are expected to have profound effects on passing stars. Understanding of the potential effects on the Earth and our Solar System is dependent on a robust model of arm passage dynamics. Using a novel combination of data, we derive a model of the timings of the Solar System through the spiral arms and the relationship to arm tracers such as methanol masers. This reveals that asteroid/comet impacts are significantly clustered near the spiral arms and within specific locations of an average arm structure. The end-Permian and end-Cretaceous extinctions emerge as being located within a small star-formation region in two different arms. The start of the Solar System, greater than 4.5 Ga, occurs in the same region in a third arm. The model complements geo-chemical data in determining the relative importance of extra-Solar events in the diversification and extinction of life on Earth.

Saturn's rings are known to show remarkable real time variability in their structure. Many of which can be associated to interactions with nearby moons and moonlets. Possibly the most interesting and dynamic place in the rings, probably in the whole Solar System, is the F ring. A highly disrupted ring with large asymmetries both radially and azimuthally. Numerically non-zero components to the curl of the velocity vector field (vorticity) in the perturbed area of the F ring post encounter are witnessed, significantly above the background vorticity. Within the perturbed area rich distributions of local rotations is seen located in and around the channel edges. The gravitational scattering of ring particles during the encounter causes a significant elevated curl of the vector field above the background F ring vorticity for the first 1-3 orbital periods post encounter. After 3 orbital periods vorticity reverts quite quickly to near background levels. This new found dynamical vortex life of the ring will be of great interest to planet and planetesimals in proto-planetary disks where vortices and turbulence are suspected of having a significant role in their formation and migrations. Additionally, it is found that the immediate channel edges created by the close passage of Prometheus actually show high radial dispersions in the order ~20-50 cm/s, up to a maximum of 1 m/s. This is much greater than the value required by Toomre for a disk to be unstable to the growth of axisymmetric oscillations. However, an area a few hundred km away from the edge shows a more promising location for the growth of coherent objects.

Saturn rings are most beautiful and dynamic places in the solar system, consisting of ice particles in a constant battle between the gravitational forces of Saturn and its many moons. Fan, spiral, propellers, moonlets and streamer-channels observed by CASSINI in the F-ring have been attributed to encounters by Prometheus on the F ring, with investigations of optical thickness revealing large populations of transient moonlets. Taking into account gravitational interaction between particles and a multi-stranded F-ring structure we show that Prometheus' encounters create rotational flows, like atmospheric vortices and the self-gravity enhances the accelerated growth and size of moonlets. Vortex patches form caustics, which is a primary cause of the transient particle density clumps of 20 km width and 100 km length and they are elongated to cover an area of 1600 km by 150 km, which may eventually combine into a vortex sheet.

Saturns F-ring is a unique, narrow ring that lies (radially) close to the tidally disruptive Roche limit of water ice for Saturn. Significant work has been done that shows it to be one of the most dynamic places in the Solar System. Aggregates that are fortunate enough to form constantly battle against the strong tidal forces of Saturn and the nearby moons Prometheus and Pandora, which act to gravitationally stir up ring material. Planetary rings are also known to radially spread. Therefore, as the F ring lies at the edge of the main rings, we investigate the effect of an outwardly migrated F ring and its interaction with Prometheus. An increase in the maximum number density of particles at the channel edges is observed with decreasing local tidal environment. Radial velocity dispersions are also observed to fall below the typical escape velocity of a 150m icy moonlet (<10 cm s^(-1)) where density is enhanced, and are gravitationally unstable with Toomre parameters Q<2. Additionally, in locations of the ring where Q<2 is observed, more particles are seen to fall below or close to the critical Toomre parameter as the radial location of the ring increases.

Aim Sufficient data to describe spatial distributions of rare and threatened populations are typically difficult to obtain. For example, there are minimal modern offshore sightings of the endangered southern right whale, limiting our knowledge of foraging grounds and habitat use patterns. Using historical exploitation data of southern right whales (SRW), we aim to better understand their seasonal offshore distribution patterns in relation to broad-scale oceanography, and to predict their exposure to shipping traffic and response to global climate change. Location Australasian region between 130° W and 100° E, and 30° S and 55° S. Methods We model 19th century whaling data with boosted regression trees to determine functional responses of whale distribution relative to environmental factors. Habitat suitability maps are generated and we validate these predictions with independent historical and recent sightings. We identify areas of increased risk of ship-strike by integrating predicted whale distribution maps with shipping traffic patterns. We implement predicted ocean temperatures for the 2090–2100 decade in our models to predict changes in whale distribution due to climate change. Results Temperature in the upper 200 m, distance from the subtropical front, mixed layer depth, chlorophyll concentration and distance from ridges are the most consistent and influential predictors of whale distribution. Validation tests of predicted distributions determined generally high predictive capacity. We identify two areas of increased risk of vessel strikes and predict substantial shifts in habitat suitability and availability due to climate change. Main conclusions Our results represent the first quantitative description of the offshore foraging habitat of SRW. Conservation applications include identifying areas and causes of threats to SRW, generating effective mitigation strategies, and directing population monitoring and research efforts. Our study demonstrates the benefits of incorporating unconventional datasets such as historical exploitation data into species distribution models to inform management and help combat biodiversity loss.