Clumped-isotope-derived climate trends leading up to the end-Cretaceous mass extinction in northwest Europe

Abstract. Paleotemperature reconstructions linked to Deccan traps volcanic greenhouse gas emissions and associated feedbacks in the lead-up to the end-Cretaceous meteorite impact and extinction document local and global climate trends during a key interval of geologic history. Here, we present a new clumped-isotope-based paleotemperature record derived from fossil bivalves from the Maastrichtian type region, in southeast Netherlands and northeast Belgium. Clumped isotope data documents a mean temperature of 19.2 ± 3.8 °C, consistent with other Maastrichtian temperature estimates, and an average seawater δ18O value of −0.3 ± 0.9 ‰ VSMOW for the region during the latest Cretaceous (67.1–66.0 Ma). A notable temperature increase at ~66.4 Ma is interpreted to be a regional manifestation of the globally-defined Late Maastrichtian Warming Event, linking Deccan Traps volcanic CO2 emissions prior to the end-Cretaceous extinction to climate change in the Maastricht region. Fluctuating seawater δ18O values coinciding with temperature changes suggest alternating influences of warm, salty southern-sourced waters and cooler, fresher northern-sourced waters from the Arctic Ocean. This new paleotemperature record contributes to the understanding of regional and global climate response to large-scale volcanism and ocean circulation changes leading up to a catastrophic mass extinction.

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A Diagnostic Model of the Nordic Seas and Arctic Ocean Circulation: Quantifying the Effects of a Variable Bottom Density along a Sloping Topography

Journal of Physical Oceanography ◽

10.1175/2008jpo3862.1 ◽

2008 ◽

Vol 38 (12) ◽

pp. 2685-2703 ◽

Cited By ~ 14

Author(s):

Signe Aaboe ◽

Ole Anders Nøst

Keyword(s):

Arctic Ocean ◽

Ocean Circulation ◽

Large Scale ◽

The Arctic ◽

Diagnostic Model ◽

Large Scale Circulation ◽

Nordic Seas ◽

Variable Bottom ◽

Canadian Basin ◽

Baroclinic Transport

Abstract A linear diagnostic model, solving for the time-mean large-scale circulation in the Nordic seas and Arctic Ocean, is presented. Solutions on depth contours that close within the Nordic seas and Arctic Ocean are found from vorticity balances integrated over the areas enclosed by the contours. Climatological data for wind stress and hydrography are used as input to the model, and the bottom geostrophic flow is assumed to follow depth contours. Comparison against velocity observations shows that the simplified dynamics in the model capture many aspects of the large-scale circulation. Special attention is given to the dynamical effects of an along-isobath varying bottom density, which leads to a transformation between barotropic and baroclinic transport. Along the continental slope, enclosing both the Nordic seas and Arctic Ocean, the along-slope barotropic transport has a maximum in the Nordic seas and a minimum in the Canadian Basin with a difference of 9 Sv (1 Sv ≡ 106 m3 s−1) between the two. This is caused by the relatively lower bottom densities in the Canadian Basin compared to the Nordic seas and suggests that most of the barotropic transport entering the Arctic Ocean through the Fram Strait is transformed to baroclinic transport. A conversion from barotropic to baroclinic flow may be highly important for the slope–basin exchange in the Nordic seas and Arctic Ocean. The model has obvious shortcomings due to its simplicity. However, the simplified physics and the agreement with observations make this model an excellent framework for understanding the large-scale circulation in the Nordic seas and Arctic Ocean.

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The pliocene record of climatic change: equator-to-pole biotic response

The Paleontological Society Special Publications ◽

10.1017/s2475262200006389 ◽

1992 ◽

Vol 6 ◽

pp. 78-78

Author(s):

Thomas M. Cronin ◽

H.J. Dowsett

Keyword(s):

Ocean Circulation ◽

North Atlantic ◽

North Pacific ◽

Global Climate ◽

North Pacific Ocean ◽

Thermal Gradients ◽

High Latitudes ◽

Near Surface ◽

Temperature Changes ◽

The North

Pliocene faunal events in tropical and subtropical regions of the Americas and the Caribbean have been causally linked to global climatic events, particularly, progressive cooling and increased amplitude of climatic cycles between 3.5 and 2.0 Ma. However, the rate and magnitude of Pliocene temperature changes has been determined in only a few climate proxy records. Our study contrasts paleoceanographic conditions at 3 Ma, an extremely warm period in many areas, with conditions 2.4 Ma, a much cooler interval, in equator-to-pole transects for the North Atlantic and the North Pacific Oceans. By using microfaunal data (ostracodes from ocean margin environments and planktic foraminifers from deep sea cores), quantitative factor analytic and modern analog dissimilarity coefficient analyses were carried out on faunas from the following sections.Our studies lead to the following conclusions: (1) Equator-to-pole thermal gradients in the oceans at 3.0 Ma were not as steep as they are today, but thermal gradients at 2.4 Ma were steeper than those today; (2)At 3 Ma middle to high latitudes were substantially warmer than today, but tropical regions were about the same; (3)Substantial cooling occurred in middle and high latitudes in the western North Pacific Ocean and the western North Atlantic between 3 Ma and 2.4 Ma; (4)Ocean water temperatures off the southeastern U.S. remained the same or cooled only slightly between 3 Ma and 2.4 Ma. Our results support the hypothesis that ocean circulation changes, probably resulting from the closure of near surface water by the Isthmus of Panama, had significant impact on equator-to-pole heat transport and global climate between about 3 and 2.4 Ma. They also argue against the hypothesis that climatically induced ocean temperature changes were directly linked to a major marine extinction in the southwestern North Atlantic and Caribbean.

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The Frontier Research System for Global Change—The International Arctic Research Center (Frontier-IARC): its Origin and Tentative Science Plan

Marine Technology Society Journal ◽

10.4031/mtsj.33.1.10 ◽

1999 ◽

Vol 33 (1) ◽

pp. 81-84

Author(s):

Jinro Ukila ◽

Moloyoshi Ikeda

Keyword(s):

Climate Change ◽

Global Change ◽

Global Climate Change ◽

Large Scale ◽

Global Climate ◽

Research Effort ◽

Arctic Region ◽

Research Center ◽

The Arctic ◽

Research System

The Frontier Research System for Global Change—the International Arctic Research Center (Frontier-IARC) is a research program funded by the Frontier Research System for Global Change. The program is jointly run under a cooperative agreement between the Frontier Research System for Global Change and the University of Alaska Fairbanks. The aim of the program is to understand the role of the Arctic region in global climate change. The program concentrates its research effort initially on the areas of air-sea-ice interactions, bio-geochemical processes and the ecosystem. To understand the arctic climate system in the context of global climate change, we focus on mechanisms controlling arctic-subarctic interactions, and identify three key components: the freshwater balance, the energy balance, and the large-scale atmospheric processes. Knowledge of details of these components and their interactions will be gained through long-term monitoring, process studies, and modeling; our focus will be on the latter two categories.

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Pan-Eurasian Experiment (PEEX): towards a holistic understanding of the feedbacks and interactions in the land–atmosphere–ocean–society continuum in the northern Eurasian region

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-14421-2016 ◽

2016 ◽

Vol 16 (22) ◽

pp. 14421-14461 ◽

Cited By ~ 27

Author(s):

Hanna K. Lappalainen ◽

Veli-Matti Kerminen ◽

Tuukka Petäjä ◽

Theo Kurten ◽

Aleksander Baklanov ◽

...

Keyword(s):

Research Agenda ◽

Large Scale ◽

System Analysis ◽

Global Climate ◽

The Arctic ◽

Research Approach ◽

Natural Environments ◽

System Perspective ◽

Holistic Understanding ◽

Eurasian Region

Abstract. The northern Eurasian regions and Arctic Ocean will very likely undergo substantial changes during the next decades. The Arctic–boreal natural environments play a crucial role in the global climate via albedo change, carbon sources and sinks as well as atmospheric aerosol production from biogenic volatile organic compounds. Furthermore, it is expected that global trade activities, demographic movement, and use of natural resources will be increasing in the Arctic regions. There is a need for a novel research approach, which not only identifies and tackles the relevant multi-disciplinary research questions, but also is able to make a holistic system analysis of the expected feedbacks. In this paper, we introduce the research agenda of the Pan-Eurasian Experiment (PEEX), a multi-scale, multi-disciplinary and international program started in 2012 (https://www.atm.helsinki.fi/peex/). PEEX sets a research approach by which large-scale research topics are investigated from a system perspective and which aims to fill the key gaps in our understanding of the feedbacks and interactions between the land–atmosphere–aquatic–society continuum in the northern Eurasian region. We introduce here the state of the art for the key topics in the PEEX research agenda and present the future prospects of the research, which we see relevant in this context.

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Simulation of the Arctic—North Atlantic Ocean Circulation with a Two-Equation K-Omega Turbulence Parameterization

Journal of Marine Science and Engineering ◽

10.3390/jmse6030095 ◽

2018 ◽

Vol 6 (3) ◽

pp. 95 ◽

Cited By ~ 1

Author(s):

Sergey Moshonkin ◽

Vladimir Zalesny ◽

Anatoly Gusev

Keyword(s):

Prandtl Number ◽

Ocean Circulation ◽

North Atlantic ◽

Large Scale ◽

Mixed Layer Depth ◽

Ocean Dynamics ◽

Dynamics Simulation ◽

The Arctic ◽

Buoyancy Frequency ◽

Physical Factors

The results of large-scale ocean dynamics simulation taking into account the parameterization of vertical turbulent exchange are considered. Numerical experiments were carried out using k − ω turbulence model embedded to the Institute of Numerical Mathematics Ocean general circulation Model (INMOM). Both the circulation and turbulence models are solved using the splitting method with respect to physical processes. We split k − ω equations into the two stages describing transport-diffusion and generation-dissipation processes. At the generation-dissipation stage, the equation for ω does not depend on k. It allows us to solve both turbulence equations analytically that ensure high computational efficiency. The coupled model is used to simulate the hydrophysical fields of the North Atlantic and Arctic Oceans for 1948–2009. The model has a horizontal resolution of 0.25 ∘ and 40 σ -levels along the vertical. The numerical results show the model’s satisfactory performance in simulating large-scale ocean circulation and upper layer dynamics. The sensitivity of the solution to the change in the coefficients entering into the analytical solution of the k − ω model which describe the influence of some physical factors is studied. These factors are the climatic annual mean buoyancy frequency (AMBF) and Prandtl number as a function of the Richardson number. The experiments demonstrate that taking into account the AMBF improves the reproduction of large-scale ocean characteristics. Prandtl number variations improve the upper mixed layer depth simulation.

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Surface reflectivity in polar regions retrieved from TDS-1 mission data

10.5194/egusphere-egu21-13036 ◽

2021 ◽

Author(s):

Frederik Kreß ◽

Maximilian Semmling ◽

Estel Cardellach ◽

Weiqiang Li ◽

Mainul Hoque ◽

...

Keyword(s):

Remote Sensing ◽

Surface Roughness ◽

Sea Ice ◽

Large Scale ◽

Global Climate ◽

Path Loss ◽

Signal Strength ◽

Global Navigation Satellite Systems ◽

The Arctic ◽

Polar Regions

In current times of a changing global climate, a special interest is focused on the large-scale recording of sea ice. Among the existing remote sensing methods, bi- statically reflected signals of Global Navigation Satellite Systems (GNSS) could play an important role in fulfilling the task. Within this project, sensitivity of GNSS signal reflections to sea ice properties like its occurrence, sea ice thick- ness (SIT) and sea concentration (SIC) is evaluated. When getting older, sea ice tends go get thicker. Because of decreasing salinity, i.e. less permittivity, as well as relatively higher surface roughness of older ice, it can be assumed that reflected signal strength decreases with increasing SIT. The reflection data used were recorded in the years 2015 and 2016 by the TechDemoSat-1 (TDS-1) satellite over the Arctic and Antarctic. It includes a down-looking antenna for the reflected as well as an up-looking antenna dedicated to receive the direct sig- nal. The raw data, provided by the manufacturer SSTL, were pre-processed by IEEC/ICE-CSIC to derive georeferenced signal power values. The reflectivity was estimated by comparing the power of the up- and down-looking links. The project focuses on the signal link budget to apply necessary corrections. For this reason, the receiver antenna gain as well as the Free-Space Path Loss (FSPL) were calculated and applied for reflectivity correction. Differences of nadir and zenith antenna FSPL and gain show influence of up to 6 dB and &#8722;9 dB to 9 dB respectively on the recorded signal strength. All retrieved reflectivity values are compared to model predictions based on Fresnel coefficients but also to avail- able ancillary truth data of other remote sensing missions to identify possible patterns: SIT relations are investigated using Level-2 data of the Soil Moisture and Ocean Salinity (SMOS) satellite. The SIC comparison was done with an AMSR-2 product. The results show sensitivity of the reflectivity value to both SIT and SIC simultaneously, whereby the surface roughness is also likely to have an influence. This on-going study aims at the consolidation of retrieval algorithms for sea-ice observation. The resolution of different ice types and the retrieval of SIT and SIC based on satellite data is a challenge for future work in this respect.

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Causes and consequences of Southern Ocean change: the IPCC SROCC assessment

10.5194/egusphere-egu2020-164 ◽

2020 ◽

Author(s):

Michael Meredith ◽

Martin Sommerkorn ◽

Sandra Cassotta ◽

Chris Derksen ◽

Alexey Ekaykin ◽

...

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Sea Level ◽

Ocean Circulation ◽

Global Climate ◽

Ice Sheets ◽

The Arctic ◽

Polar Regions ◽

Ice Shelves

Climate change in the polar regions exerts a profound influence both locally and over all of our planet.&#160; Physical and ecosystem changes influence societies and economies, via factors that include food provision, transport and access to non-renewable resources.&#160; Sea level, global climate and potentially mid-latitude weather are influenced by the changing polar regions, through coupled feedback processes, sea ice changes and the melting of snow and land-based ice sheets and glaciers.Reflecting this importance, the IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) features a chapter highlighting past, ongoing and future change in the polar regions, the impacts of these changes, and the possible options for response.&#160; The role of the polar oceans, both in determining the changes and impacts in the polar regions and in structuring the global influence, is an important component of this chapter.With emphasis on the Southern Ocean and through comparison with the Arctic, this talk will outline key findings from the polar regions chapter of SROCC. It will synthesise the latest information on the rates, patterns and causes of changes in sea ice, ocean circulation and properties. It will assess cryospheric driving of ocean change from ice sheets, ice shelves and glaciers, and the role of the oceans in determining the past and future evolutions of polar land-based ice. The implications of these changes for climate, ecosystems, sea level and the global system will be outlined.

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The ocean response to changes of the Greenland Ice sheet in a warming climate

10.5194/egusphere-egu2020-21261 ◽

2020 ◽

Author(s):

Marianne S. Madsen ◽

Shuting Yang ◽

Christian Rodehacke ◽

Guðfinna Aðalgeirsdóttir ◽

Synne H. Svendsen ◽

...

Keyword(s):

Mass Loss ◽

Ocean Circulation ◽

Large Scale ◽

Climate Model ◽

Variable Mass ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Model System ◽

Meridional Overturning Circulation ◽

The Arctic

During recent decades, increased and highly variable mass loss from the Greenland ice sheet has been observed, implying that the ice sheet can respond to changes in ocean and atmospheric conditions on annual to decadal time scales. Changes in ice sheet topography and increased mass loss into the ocean may impact large scale atmosphere and ocean circulation. Therefore, coupling of ice sheet and climate models, to explicitly include the processes and feedbacks of ice sheet changes, is needed to improve the understanding of ice sheet-climate interactions.Here, we present results from the coupled ice sheet-climate model system, EC-Earth-PISM. The model consists of the atmosphere, ocean and sea-ice model system EC-Earth, two-way coupled to the Parallel Ice Sheet Model, PISM. The surface mass balance (SMB) is calculated within EC-Earth, from the precipitation, evaporation and surface melt of snow and ice, to ensure conservation of mass and energy. The ice sheet model, PISM, calculates ice dynamical changes in ice discharge and basal melt as well as changes in ice extent and thickness. Idealized climate change experiments have been performed starting from pre-industrial conditions for a) constant forcing (pre-industrial control); b) abruptly quadrupling the CO2 concentration; and c) gradually increasing the CO2 concentration by 1% per year until 4xCO2 is reached. &#160;All three experiments are run for 350 years.Our results show a significant impact of the interactive ice sheet component on heat and fresh water fluxes into the Arctic and North Atlantic Oceans. The interactive ice sheet causes freshening of the Arctic Ocean and affects deep water formation, resulting in a significant delay of the recovery of the Atlantic Meridional Overturning Circulation (AMOC) in the coupled 4xCO2 experiments, when compared with uncoupled experiments.

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The Norwegian node for the European Multidisciplinary Seafloor and water column Observatory

10.5194/egusphere-egu2020-7248 ◽

2020 ◽

Author(s):

Thibaut Barreyre ◽

Ilker Fer ◽

Bénédicte Ferré

Keyword(s):

Water Column ◽

Ocean Circulation ◽

Large Scale ◽

Water Mass ◽

Critical Role ◽

Meridional Overturning Circulation ◽

The Arctic ◽

Global Ocean ◽

Fram Strait ◽

Nordic Seas

NorEMSO is a coordinated, large-scale deep-ocean observation facility to establish the Norwegian node for the European Multidisciplinary Seafloor and water column Observatory (EMSO). The project aims to explore the under-sampled Nordic Seas to gain a better understanding of the critical role that they play in our climate system and global ocean circulation. An overarching scientific objective is to better understand the drivers for the temporal and spatial changes of water mass transformations, ocean circulation, acidification and thermo-chemical exchanges at the seafloor in the Nordic Seas, and to contribute to improvement of models and forecasting by producing and making available high quality, near real time data. NorEMSO will achieve this by combining expansion of existing and establishment of new observatory network infrastructure, as well as its coordination and integration into EMSO.NorEMSO comprises of three main components: moored observatories, gliders, and seafloor and water column observatory at the Mohn Ridge (EMSO-Mohn).Moored observation systems include an array of four moored observatories located at key positions in the Nordic Seas (Svin&#248;y, Station M, South Cape, and central Fram Strait).Gliders will be operated along five transects across both the Norwegian and the Greenland Seas to monitor circulation and water mass properties at those key locations. Transects in the Norwegian and Lofoten basins will focus on monitoring the Norwegian Atlantic Current, and a transect in Fram Strait will monitor properties and variability in the return Atlantic Water along the Polar Front in the northern Nordic Seas. In addition, transects in the Greenland and Iceland Seas will address the water mass transformation processes through wintertime open ocean convection, and the southbound transport of surface water from the Arctic Ocean and dense water that feeds the lower limb of the Atlantic Meridional Overturning Circulation in the East Greenland Current.EMSO-Mohn will establish, at the newly discovered hydrothermal site on the Mohn Ridge, a fixed-point seabed-water-column-coupled and wireless observatory with a multidisciplinary approach &#8211; from geophysics and physical oceanography to ecology and microbiology. It is primarily directed at understanding hydrothermal fluxes and associated hydrothermal plume dynamics in the water column and how it disperses in an oceanographic front over the Mohn Ridge.Following EMSO philosophy, NorEMSO will provide data and platforms to a large and diverse group of users, from scientists and industries to institutions and policy makers. The observations will serve climate research, ocean circulation understanding, numerical operational models, design of environmental policies, and education.

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Interannual characteristics of an 80 km resolution diagnostic Arctic ice–ocean model

Annals of Glaciology ◽

10.1017/s0260305500009861 ◽

1991 ◽

Vol 15 ◽

pp. 155-162 ◽

Cited By ~ 4

Author(s):

John E. Ries ◽

William D. Hibler

Keyword(s):

Ocean Circulation ◽

Large Scale ◽

Eddy Viscosity ◽

Barents Sea ◽

Arctic Basin ◽

Ocean Model ◽

The Arctic ◽

Atmospheric Forcing ◽

Ice Edge ◽

Arctic Ice

Seasonal simulations with large-scale coupled ice–ocean models have reproduced many features of the ice and ocean circulation of the Arctic Ocean and the Greenland and Norwegian seas (e.g. Hibler and Bryan, 1987; Semtner, 1987). However, the crude resolution and high lateral eddy viscosity used by these models prevent the simulation of many of the smaller-scale seasonal features and tend to produce sluggish circulation. Similarly, the use of a single year’s atmospheric forcing prevents the simulation of features on an interannual time-scale. As an initial step towards addressing these issues, an 80 km diagnostic Arctic ice–ocean model is constructed and integrated over a three-year period using daily atmospheric forcing to drive the model. To examine the effect of topographic resolution and eddy viscosity on model results, similar simulations were performed with a 160 km-resolution model. The results of these simulations are compared with one another, with buoy drift in the Arctic Basin, and with observed ice-edge variations. The model results proved most sensitive to changes in horizontal resolution. The 80 km results provided a more realistic and robust circulation in most areas of the Arctic and improved the modelled ice edge in the Barents Sea, while also successfully simulating the interannual variation in the region. Although it performed better than the 160 km model, the 80 km model still produced too large an ice extent in the Greenland Sea. No significant improvement in the ice-edge prediction was observed by varying the lateral eddy viscosity. The results indicate that problems remain in the vertical resolution in shallow regions, in treating penetrative convection, and in the simulation of inflow into the Arctic Basin through the Fram Strait.

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