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| Open AccessUnprecedented decline of Arctic sea ice outflow in 2018
Fram Strait is the major gateway connecting the Arctic Ocean and North Atlantic Ocean, where nearly 90% of the sea ice export from the Arctic Ocean takes place. Here, the authors show that in 2018, ice export showed an unprecedented decline since at least the 1990s, attributed to ongoing Arctic-wide ice thinning and regional-scale atmospheric anomalies.
- Hiroshi Sumata
- , Laura de Steur
- & Olga Pavlova
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Article
| Open AccessSeasonal variability of ocean circulation near the Dotson Ice Shelf, Antarctica
The intrusion of relatively warm water is causing the recent rapid thinning of the Dotson ice shelf, West Antarctica. Here, the authors analyzed two-years of mooring data from the Dotson ice shelf front and found that seasonal variability of the ocean circulation and ocean surface stress are the main causes of variability in heat transport.
- H. W. Yang
- , T.-W. Kim
- & Y.-K. Cho
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| Open AccessRecent upper Arctic Ocean warming expedited by summertime atmospheric processes
Low-frequency internal atmospheric variability accounts for about one quarter of observed Arctic Ocean warming over the past four decades and 60% of the accelerated warming from 2000 to 2018.
- Zhe Li
- , Qinghua Ding
- & Axel Schweiger
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| Open AccessStratification constrains future heat and carbon uptake in the Southern Ocean between 30°S and 55°S
The heat and carbon uptakes in the Southern Ocean between 30°S and 55°S are critical for mitigating climate change. Here the authors find that projection uncertainties of both uptakes are reduced drastically when using the water column stability as an emergent constraint.
- Timothée Bourgeois
- , Nadine Goris
- & Jerry F. Tjiputra
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| Open AccessIce front retreat reconfigures meltwater-driven gyres modulating ocean heat delivery to an Antarctic ice shelf
Glacial melt can modify heat transport, and therefore ocean processes, associated with ice front retreat, as revealed by direct observations from the Pine Island Bay region of Antarctica.
- Seung-Tae Yoon
- , Won Sang Lee
- & Alexander T. Bradley
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| Open AccessSea-ice retreat suggests re-organization of water mass transformation in the Nordic and Barents Seas
Water mass transformation in the Nordic and Barents Seas is important for the Atlantic Meridional Overturning Circulation (AMOC). Here, the authors show increases in air-sea heat fluxes linked to sea ice retreat along the boundary currents of the Nordic and Barents Seas that could influence how the AMOC reacts to climate change.
- G. W. K. Moore
- , K. Våge
- & R. S. Pickart
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| Open AccessStorms drive outgassing of CO2 in the subpolar Southern Ocean
Storms dominate the subpolar Southern Ocean, where upwelling CO2 drives outgassing that impacts global CO2 budget, yet how storms modify this outgassing is unknown. Here, the authors present coupled atmosphere-ocean observations to show how storm-driven ocean mixing and circulation cause substantial CO2 variability and outgassing.
- Sarah-Anne Nicholson
- , Daniel B. Whitt
- & Pedro M. S. Monteiro
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| Open AccessSea-ice derived meltwater stratification slows the biological carbon pump: results from continuous observations
The North Atlantic biological pump has the most intense absorption of C globally, but how this will fare in light of climate changes (especially sea-ice melting) is poorly understood. Here the authors present a 24-month continuous time series of physical, chemical, and biological observations in the Fram Strait.
- Wilken-Jon von Appen
- , Anya M. Waite
- & Antje Boetius
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Article
| Open AccessGateway-driven weakening of ocean gyres leads to Southern Ocean cooling
The role of Southern Ocean gateways contributing to the Eocene-Oligocene climate transition is still debated. Here, the authors present high-resolution ocean simulations to show that gateways opening led to a reorganization of ocean circulation, heat transport and Antarctic surface water cooling.
- Isabel Sauermilch
- , Joanne M. Whittaker
- & Joseph H. LaCasce
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Article
| Open AccessDynamic Europa ocean shows transient Taylor columns and convection driven by ice melting and salinity
The deep ocean of Jupiter’s moon Europa is one of the prime candidates for finding life outside Earth within the solar system. Here, the authors show that Europa’s ocean is energetic, yet weakly stratified with its density dominated by salinity effects.
- Yosef Ashkenazy
- & Eli Tziperman
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Article
| Open AccessIndian Ocean Dipole leads to Atlantic Niño
The Atlantic Niño is an important mode of tropical Atlantic variability that influences the climate conditions in surrounding areas. Here, the authors use observational data and model simulations to show that positive phases of the Indian Ocean Dipole can trigger Atlantic Niño events.
- Lei Zhang
- & Weiqing Han
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Article
| Open AccessLagrangian betweenness as a measure of bottlenecks in dynamical systems with oceanographic examples
The motion of the ocean transports microorganisms, pollutants, and other particles, but these are challenging to track. Here the authors present a Lagrangian form of Betweenness Centrality which identifies bottlenecks in dynamical systems and fluid flows as well as an interpretation of diversity hotspots.
- Enrico Ser-Giacomi
- , Alberto Baudena
- & Emilio Hernández-García
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| Open AccessAtmospheric wavenumber-4 driven South Pacific marine heat waves and marine cool spells
Marine heat waves and cold spells threaten ocean ecosystems and are thought to be increasing with climate change. Here the author shows that MHW/MCS in the Tasman Sea co-occur with corresponding events in the Atlantic, Indian, and Pacific Oceans, and these southern hemisphere events are driven by stalling of a global wavenumber-4 atmospheric wave.
- Stephen M. Chiswell
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| Open Access20th century cooling of the deep ocean contributed to delayed acceleration of Earth’s energy imbalance
Cooling of the global ocean below 2000 m counteracted some of the warming of the shallow ocean over much of the late 20th century. Here the authors show that this trend has shifted to warming, leading the deep ocean to absorb a meaningful fraction of total ocean heat during the 21st century.
- A. Bagnell
- & T. DeVries
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| Open AccessDiffusion controls the ventilation of a Pacific Shadow Zone above abyssal overturning
The deep North Pacific is the end of the road for global ocean circulation, but the circulation patterns and ventilation are poorly understood. Here the authors show that diffusive transports both along and across density layers play a leading role in returning 1,400 year old water to the surface.
- Mark Holzer
- , Tim DeVries
- & Casimir de Lavergne
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| Open AccessThermohaline structure and circulation beneath the Langhovde Glacier ice shelf in East Antarctica
Basal melting of ice shelves is the principal driver of recent ice mass loss in Antarctica. The study reports comprehensive structures of temperature, salinity and current under an ice shelf in East Antarctica obtained by borehole measurements.
- Masahiro Minowa
- , Shin Sugiyama
- & Shigeru Aoki
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Article
| Open AccessVelocity bias in intrusive gas-liquid flow measurements
Estimating velocities in gas liquid flows is of importance in many engineering applications. Hohermuth et al. show that previous bubble velocities obtained from intrusive probes have been underestimated and provide a correction scheme for more accurate velocity measurements.
- B. Hohermuth
- , M. Kramer
- & D. Valero
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| Open AccessClimate pacing of millennial sea-level change variability in the central and western Mediterranean
How sea-level in the western Mediterranean reacts to climate changes is not well known. Here, the authors present a regional reconstruction and show that temperatures influenced sea-level change rates during the Holocene, while recent sea-level rise is happening faster than during any other period of the last 4000 years.
- Matteo Vacchi
- , Kristen M. Joyse
- & Alessio Rovere
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| Open AccessGlobal coastal attenuation of wind-waves observed with radar altimetry
Reprocessed data from satellite altimetry show that the mean significant wave height decreases globally by 22% on average from 30 km to 3 km from the coast. By combining these data with wave period from reanalysis, we estimate a mean reduction of 38% concerning the mean wave energy flux.
- Marcello Passaro
- , Mark A. Hemer
- & Florian Seitz
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| Open AccessA global analysis of extreme coastal water levels with implications for potential coastal overtopping
As sea levels rise, coasts are being increasingly threatened by overtopping caused by the combination of sea level rise, storm surge and wave runup. Here the authors find that global coastal overtopping has increased by over 50% in the last two decades, and under a RCP 8.5 scenario this could increase up to 50 times by 2100 compared to today.
- Rafael Almar
- , Roshanka Ranasinghe
- & Elodie Kestenare
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| Open AccessSubpolar North Atlantic western boundary density anomalies and the Meridional Overturning Circulation
Western boundary current variability in the subpolar North Atlantic is thought to reflect interior convection changes and determine Atlantic Meridional Overturning Circulation variability. Here, the authors show with an extended OSNAP time series that neither linkage is robust due to the complex dynamics in the region.
- F. Li
- , M. S. Lozier
- & C. Zhou
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| Open AccessObserved interannual changes beneath Filchner-Ronne Ice Shelf linked to large-scale atmospheric circulation
New data from five hot-water drilled boreholes show how atmospheric anomalies affect the circulation beneath Filchner-Ronne Ice Shelf on multi-year time scales. The apparent link of the dense water formation to remote teleconnections is an important step for better predicting contributions to future sea level rise from this sector of Antarctica.
- Tore Hattermann
- , Keith W. Nicholls
- & Torsten Kanzow
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| Open AccessThe poleward enhanced Arctic Ocean cooling machine in a warming climate
The Arctic Ocean cooling machine, currently the Barents Sea, plays a crucial role in both regulating the climate and determining the deep ocean circulation. Here the authors show that the efficiency of the cooling machine is poleward enhanced in a warming climate, which pushes Arctic Atlantification poleward.
- Qi Shu
- , Qiang Wang
- & Fangli Qiao
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| Open AccessEconomic damages from Hurricane Sandy attributable to sea level rise caused by anthropogenic climate change
Sea level rise amplifies coastal storm impacts, but the role of anthropogenic climate change is poorly resolved. Here the authors reassess Hurricane Sandy, using a dynamic flood model to show that anthropogenic sea level rise added a central estimate of $8 billion in damages.
- Benjamin H. Strauss
- , Philip M. Orton
- & Sergey Vinogradov
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Article
| Open AccessA warm jet in a cold ocean
Warming ocean water plays a significant role in accelerating Arctic sea ice melt. Here the authors present detailed observations of warm water of Pacific origin entering and diving beneath the Arctic ocean surface, and explore the dynamical processes governing its evolution.
- Jennifer A. MacKinnon
- , Harper L. Simmons
- & Kevin R. Wood
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| Open AccessTwo-timescale response of a large Antarctic ice shelf to climate change
New simulations find that one of Antarctica’s largest ice shelves, the Filchner–Ronne, may be less vulnerable to climate change than previously thought. Melting of the ice shelf initially decreases for many decades, and only increases when global warming exceeds approximately 7 °C.
- Kaitlin A. Naughten
- , Jan De Rydt
- & Jeff K. Ridley
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| Open AccessOcean fronts and eddies force atmospheric rivers and heavy precipitation in western North America
Atmospheric rivers are responsible for much of the poleward water vapour transport in the mid-latitudes and can cause extreme precipitation after landfall. Here, the authors show that ocean fronts and eddies can influence atmospheric rivers and increase the associated precipitation along the North American west coast.
- Xue Liu
- , Xiaohui Ma
- & Christina M. Patricola
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Article
| Open AccessLabrador Sea freshening linked to Beaufort Gyre freshwater release
The Beaufort Gyre in the western Arctic Ocean has accumulated a large amount of freshwater. Here, the authors show that a historical release in the 1980s resulted in a strong freshening of the western Labrador Sea, suggesting that a future release of the current freshwater volume could even be more impactful.
- Jiaxu Zhang
- , Wilbert Weijer
- & Milena Veneziani
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| Open AccessWidespread increase in dynamic imbalance in the Getz region of Antarctica from 1994 to 2018
The Getz region of West Antarctica is losing ice at an increasing rate; however, the forcing mechanisms remain unclear. Here we show for the first time that since 1994, widespread speedup has occurred on the majority of glaciers in the Getz drainage basin, with some glaciers speeding up by over 44 %.
- Heather L. Selley
- , Anna E. Hogg
- & Tae-Wan Kim
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| Open AccessReconciling global mean and regional sea level change in projections and observations
Evaluating sea-level projections used by the IPCC is challenging due to the short overlap with measurements. Here, the authors show that observed global and regional sea-level trends confirm projections and that the acceleration of sea-level rise is between the one expected from the scenarios RCP4.5 and RCP8.5.
- Jinping Wang
- , John A. Church
- & Xianyao Chen
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Article
| Open AccessDeep learning to infer eddy heat fluxes from sea surface height patterns of mesoscale turbulence
Eddy heat fluxes crucially affect large-scale oceanic currents but are challenging to monitor on a global scale. Here the authors develop a Deep Learning model to predict the eddy heat fluxes from sea surface height data only, bypassing the need for simultaneous observations of the deep ocean.
- Tom M. George
- , Georgy E. Manucharyan
- & Andrew F. Thompson
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| Open AccessSouthern Ocean in-situ temperature trends over 25 years emerge from interannual variability
The Southern Ocean takes up the most heat and carbon, yet because of its remote and harsh location, it remains relatively sparsely measured. Here the authors use a 25 year temperature series which shows a clear, long term trend in subsurface warming that emerges from interannual variability.
- Matthis Auger
- , Rosemary Morrow
- & Rebecca Cowley
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Article
| Open AccessWeak tides during Cryogenian glaciations
How and why the ‘Snowball Earth’ occurred during the Cryogenian period is debated. Here, the authors show that the cryogenian ocean hosted diminished tidal amplitudes and associated energy dissipation rates, reaching 10-50% of today’s rates thus perhaps contributing to prolonged glaciations.
- J. A. Mattias Green
- , Hannah S. Davies
- & Christopher Scotese
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| Open AccessIceberg melting substantially modifies oceanic heat flux towards a major Greenlandic tidewater glacier
Iceberg melting releases large volumes of freshwater in fjords, yet the impact on oceanic heat delivery to tidewater glaciers is unknown. Here the authors show that iceberg melting invigorates fjord circulation in a large, iceberg-congested fjord, thereby increasing oceanic heat delivery to its tidewater glaciers.
- B. J. Davison
- , T. R. Cowton
- & A. J. Sole
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| Open AccessThe Iceland-Faroe Slope Jet: a conduit for dense water toward the Faroe Bank Channel overflow
Dense water from the Nordic Seas sustains the Atlantic Meridional Overturning Circulation, yet the upstream pathways are not fully known. Here, the authors provide evidence of a deep current between Iceland and the Faroe Islands, which supplies 50% of the transport through the Faroe Bank Channel overflow.
- Stefanie Semper
- , Robert S. Pickart
- & Bogi Hansen
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| Open AccessSources and upstream pathways of the densest overflow water in the Nordic Seas
Overflow water is an important part of the Atlantic Meridional Overturning Circulation, yet how it reaches the Greenland-Scotland Ridge is not fully known. Here, the authors show that the interior of the Greenland Sea gyre is the primary wintertime source of the densest portion of both Denmark Strait and Faroe Bank Channel overflows.
- Jie Huang
- , Robert S. Pickart
- & Fanghua Xu
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| Open AccessModulation of late Pleistocene ENSO strength by the tropical Pacific thermocline
How the El Niño Southern Oscillation depends on the background conditions is not well known. Here, the authors present individual foraminifera distributions which show that central Pacific variability is related to the warmth and depth of the thermocline across varying climate background conditions over the past ~285,000 years.
- Gerald T. Rustic
- , Pratigya J. Polissar
- & Sarah M. White
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Article
| Open AccessImpact of tides and sea-level on deep-sea Arctic methane emissions
This study investigates the effect of changing sea level on deep sea gas emissions in the Arctic. The results show that small decreases in sea-level favors gas release. This implies that sea-level rise may partially counterbalance the effect of warming oceans on gas emissions overall.
- Nabil Sultan
- , Andreia Plaza-Faverola
- & Jochen Knies
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| Open AccessCompounding impact of severe weather events fuels marine heatwave in the coastal ocean
Exposure to extreme events is a major concern in coastal regions where human populations and stressed ecosystems are at risk to such phenomena. Here the authors show a marine heatwave on the continental shelf resulted from a novel set of compounding effects due to a tropical storm followed by an atmospheric heatwave.
- B. Dzwonkowski
- , J. Coogan
- & T. Lee
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Article
| Open AccessMeltwater sediment transport as the dominating process in mid-latitude trough mouth fan formation
Trough mouth fans are created via repeated glacigenic sediment transport from ice sheets. Here the authors use 3D seismic reflection data to present a formation model for the North Sea Fan and find that exceptionally large volumes of meltwater may mean that freshwater supply is underestimated during glacial cycles.
- Benjamin Bellwald
- , Sverre Planke
- & Reidun Myklebust
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Article
| Open AccessDynamics for El Niño-La Niña asymmetry constrain equatorial-Pacific warming pattern
The asymmetry between El Niño and La Niña episodes in the tropical Pacific is often not well represented in models. Here, the authors show that this asymmetry is related to subsurface nonlinear dynamical heating and that a realistic representation of this process can potentially improve tropical climate projections.
- Michiya Hayashi
- , Fei-Fei Jin
- & Malte F. Stuecker
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| Open AccessInsights into projected changes in marine heatwaves from a high-resolution ocean circulation model
Marine heatwaves are likely to intensify in a warmer world, but prediction of these events is hampered by course-scale modeling. Here the authors develop a fine scale, global model which shows that marine heatwaves will amplify with greater spatial variability, particularly at western boundary regions.
- Hakase Hayashida
- , Richard J. Matear
- & Xuebin Zhang
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Article
| Open AccessStrong ice-ocean interaction beneath Shirase Glacier Tongue in East Antarctica
East Antarctic ice shelves typically have cold ice cavities with low basal melt rates. Here the authors direct observational evidence of high basal melt rates beneath Shirase Glacier Tongue in East Antarctica, driven by inflowing warm water guided by a deep continuous trough extending to the continental slope.
- Daisuke Hirano
- , Takeshi Tamura
- & Shigeru Aoki
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Article
| Open AccessDual clumped isotope thermometry resolves kinetic biases in carbonate formation temperatures
Some palaeotemperature proxies suffer from inaccuracies related to kinetic fractionations occurring during carbonate mineral growth. Here, the authors show that dual clumped isotope thermometry can identify the origin of these kinetic biases and allows for the reconstruction of accurate environmental temperatures.
- David Bajnai
- , Weifu Guo
- & Jens Fiebig
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Article
| Open AccessLikely weakening of the Florida Current during the past century revealed by sea-level observations
Understanding trends in ocean circulation and dynamics is hampered by a lack of long-term records. Here the author uses probabilistic reanalysis of available data to show that transport by the Florida Current has declined over the past 110 years, indicating a slowdown of Atlantic Ocean circulation.
- Christopher G. Piecuch
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Article
| Open AccessCosmogenic exposure dating reveals limited long-term variability in erosion of a rocky coastline
Predicted sea-level rise is widely anticipated to lead to increased coastal erosion, however, assessing how rocky coasts will respond to changes in marine conditions is difficult to constrain. Here, the authors find that a North Yorkshire rocky cliff has been eroding at a similar rate over the last 7 kyr, and they do not observe an increase in erosion rates in response to modern sea level rise.
- Zuzanna M. Swirad
- , Nick J. Rosser
- & John Barlow
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| Open AccessDiscovery of an unrecognized pathway carrying overflow waters toward the Faroe Bank Channel
The authors show that overflow waters flowing toward the Faroe Bank Channel can take a previously unidentified path to the Faroe-Shetland Channel where it joins an unrecognized deep-reaching jet located along its eastern rather than its western boundary.
- Léon Chafik
- , Hjálmar Hátún
- & Barbara Berx
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| Open AccessSearch and rescue at sea aided by hidden flow structures
Every year, hundreds of people die at sea because of vessel accidents, and a key challenge in reducing these fatalities is to make Search and Rescue (SAR) planning more efficient. Here, the authors uncover hidden flow features that attract floating objects, providing specific information for optimal SAR planning.
- Mattia Serra
- , Pratik Sathe
- & George Haller
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Article
| Open AccessNon-linear interaction modulates global extreme sea levels, coastal flood exposure, and impacts
The non-linear interaction between tide and non-tidal residual impacts current and future extreme water levels. Here, based on 620 gauge records, the authors find a large non-linear interaction in the US East Coast, North Sea and parts of southern Japan, that results in a reduction of extreme sea levels.
- Arne Arns
- , Thomas Wahl
- & Jürgen Jensen