The Relationship of Weddell Polynya and Open-Ocean Deep Convection to the Southern Hemisphere Westerlies
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Fronts in the World Ocean's Large Marine Ecosystems. ICES CM 2007
- 1 - This paper can be freely cited without prior reference to the authors International Council ICES CM 2007/D:21 for the Exploration Theme Session D: Comparative Marine Ecosystem of the Sea (ICES) Structure and Function: Descriptors and Characteristics Fronts in the World Ocean’s Large Marine Ecosystems Igor M. Belkin and Peter C. Cornillon Abstract. Oceanic fronts shape marine ecosystems; therefore front mapping and characterization is one of the most important aspects of physical oceanography. Here we report on the first effort to map and describe all major fronts in the World Ocean’s Large Marine Ecosystems (LMEs). Apart from a geographical review, these fronts are classified according to their origin and physical mechanisms that maintain them. This first-ever zero-order pattern of the LME fronts is based on a unique global frontal data base assembled at the University of Rhode Island. Thermal fronts were automatically derived from 12 years (1985-1996) of twice-daily satellite 9-km resolution global AVHRR SST fields with the Cayula-Cornillon front detection algorithm. These frontal maps serve as guidance in using hydrographic data to explore subsurface thermohaline fronts, whose surface thermal signatures have been mapped from space. Our most recent study of chlorophyll fronts in the Northwest Atlantic from high-resolution 1-km data (Belkin and O’Reilly, 2007) revealed a close spatial association between chlorophyll fronts and SST fronts, suggesting causative links between these two types of fronts. Keywords: Fronts; Large Marine Ecosystems; World Ocean; sea surface temperature. Igor M. Belkin: Graduate School of Oceanography, University of Rhode Island, 215 South Ferry Road, Narragansett, Rhode Island 02882, USA [tel.: +1 401 874 6533, fax: +1 874 6728, email: [email protected]]. -
Manuscript Text Click Here to Download Manuscript LCDW-Sub-V4.4-Text.Docx Click Here to View Linked References 1 2 3 4 5 6 7
Manuscript text Click here to download Manuscript LCDW-sub-v4.4-text.docx Click here to view linked References 1 Modification of the Deep Salinity-Maximum in the Southern Ocean by Circulation in the Antarctic 1 2 2 Circumpolar Current and the Weddell Gyre 3 4 3 Matthew Donnelly1, Harry Leach2 and Volker Strass3 5 6 4 1British Oceanographic Data Centre, National Oceanography Centre, Joseph Proudman Building, 6 Brownlow 7 8 5 Street, Liverpool, L3 5DA, UK 9 10 6 2Department of Earth, Ocean and Ecological Sciences, University of Liverpool, 4 Brownlow Street, Liverpool, 11 12 7 L69 3GP, UK 13 14 8 3Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Postfach 12 01 61, D-27515 15 16 9 Bremerhaven, Germany 17 18 10 Corresponding author: Matthew Donnelly 19 20 11 E-mail: [email protected] 21 22 12 Telephone: +44 151 795 4892 23 24 13 25 26 14 Abstract 27 28 29 15 The evolution of the deep salinity-maximum associated with the Lower Circumpolar Deep Water (LCDW) is 30 31 16 assessed using a set of 37 hydrographic sections collected over a 20 year period in the Southern Ocean as part of 32 33 17 the WOCE/CLIVAR programme. A circumpolar decrease in the value of the salinity maximum is observed 34 35 18 eastwards from the North Atlantic Deep Water (NADW) in the Atlantic sector of the Southern Ocean through 36 37 19 the Indian and Pacific sectors to Drake Passage. Isopycnal mixing processes are limited by circumpolar fronts, 38 39 20 and in the Atlantic sector this acts to limit the direct poleward propagation of the salinity signal. -
Years at the Amery Ice Shelf in September 2019
https://doi.org/10.5194/tc-2020-219 Preprint. Discussion started: 19 August 2020 c Author(s) 2020. CC BY 4.0 License. 1 Atmospheric extremes triggered the biggest calving event in more than 50 2 years at the Amery Ice shelf in September 2019 3 4 Diana Francis 1*, Kyle S. Mattingly 2, Stef Lhermitte 3, Marouane Temimi 1, Petra Heil 4 5 6 1 Khalifa University of Science and Technology, P. O. Box 54224, Abu Dhabi, United Arab 7 Emirates. 8 2 Institute of Earth, Ocean, and Atmospheric Sciences, Rutgers University, New Brunswick, NJ, 9 USA. 10 3 Department of Geoscience and Remote Sensing, Delft University of Technology, Mekelweg 5, 11 2628 CD Delft, Netherlands. 12 4 University of Tasmania, Hobart, Tasmania 7001, Australia. 13 14 * Corresponding Author: [email protected]. 15 16 Abstract 17 Ice shelf instability is one of the main sources of uncertainty in Antarctica’s contribution to future 18 sea level rise. Calving events play crucial role in ice shelf weakening but remain unpredictable and 19 their governing processes are still poorly understood. In this study, we analyze the unexpected 20 September 2019 calving event from the Amery Ice Shelf, the largest since 1963 and which 21 occurred almost a decade earlier than expected, to better understand the role of the atmosphere in 22 calving. We find that atmospheric extremes provided a deterministic role in this event. The calving 23 was triggered by the occurrence of a series of anomalously-deep and stationary explosive twin 24 polar cyclones over the Cooperation and Davis Seas which generated strong offshore winds 25 leading to increased sea ice removal, fracture amplification along the pre-existing rift, and 26 ultimately calving of the massive iceberg. -
A Destabilizing Thermohaline Circulation–Atmosphere–Sea Ice
642 JOURNAL OF CLIMATE VOLUME 12 NOTES AND CORRESPONDENCE A Destabilizing Thermohaline Circulation±Atmosphere±Sea Ice Feedback STEVEN R. JAYNE MIT±WHOI Joint Program in Oceanography, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts JOCHEM MAROTZKE Center for Global Change Science, Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 18 November 1996 and 9 March 1998 ABSTRACT Some of the interactions and feedbacks between the atmosphere, thermohaline circulation, and sea ice are illustrated using a simple process model. A simpli®ed version of the annual-mean coupled ocean±atmosphere box model of Nakamura, Stone, and Marotzke is modi®ed to include a parameterization of sea ice. The model includes the thermodynamic effects of sea ice and allows for variable coverage. It is found that the addition of sea ice introduces feedbacks that have a destabilizing in¯uence on the thermohaline circulation: Sea ice insulates the ocean from the atmosphere, creating colder air temperatures at high latitudes, which cause larger atmospheric eddy heat and moisture transports and weaker oceanic heat transports. These in turn lead to thicker ice coverage and hence establish a positive feedback. The results indicate that generally in colder climates, the presence of sea ice may lead to a signi®cant destabilization of the thermohaline circulation. Brine rejection by sea ice plays no important role in this model's dynamics. The net destabilizing effect of sea ice in this model is the result of two positive feedbacks and one negative feedback and is shown to be model dependent. To date, the destabilizing feedback between atmospheric and oceanic heat ¯uxes, mediated by sea ice, has largely been neglected in conceptual studies of thermohaline circulation stability, but it warrants further investigation in more realistic models. -
An Investigation of Antarctic Circumpolar Current Strength in Response to Changes in Climate
An Investigation of Antarctic Circumpolar Current Strength in Response to Changes in Climate Presented by Matt Laffin Presentation Outline Introduction to Marine Sediment as a Proxy Introduction to McCave paper and inference of current strength Discuss Sediment Core site Discuss sediment depositionBIG CONCEPT and oceanography of the region Discuss sorting sedimentBring process the attention and Particle of your Size audience Analyzer over a key concept using icons or Discussion of results illustrations Marine Sediment as a Proxy ● Marine sediment cores are an excellent resource to determine information about the past. ● As climatic changes occur so do changes in sediment transportation and deposition. ○ Sedimentation rates ○ Temperature ○ Biology How can we determine past ocean current strength using marine sediment? McCave et al, 1995 ● “Sortable silt” flow speed proxy ● Size distributions of sediment from the Nova Scotian Rise measured by Coulter Counter (a) Dominant 4 μm and weak 10 μm mode under slow currents (b) Silt signature after moderate currents of 5–10 cm s−1 (c) Pronounced mode in the part of the silt spectrum >10 μm after strong currents (10–15 cm s−1) McCave et al, 1995/2006 Complications to determine current strength ● Particles < 10 μm are subject to electrostatic forces which bind them ● The mean of 10–63 μm sortable silt denoted as is a more sensitive indicator of flow speed. McCave et al, 1995/2006 IODP Leg 178, Site 1096 A and B Depositional Environment Depositional Environment ● Sediment is eroded and transported -
Open-Ocean Polynyas and Deep Convection in the Southern Ocean Woo Geun Cheon1 & Arnold L
www.nature.com/scientificreports OPEN Open-ocean polynyas and deep convection in the Southern Ocean Woo Geun Cheon1 & Arnold L. Gordon 2 An open-ocean polynya is a large ice-free area surrounded by sea ice. The Maud Rise Polynya in the Received: 27 December 2018 Southern Ocean occasionally occurs during the austral winter and spring seasons in the vicinity of Maud Accepted: 18 April 2019 Rise near the Greenwich Meridian. In the mid-1970s the Maud Rise Polynya served as a precursor to Published: xx xx xxxx the more persistent, larger Weddell Polynya associated with intensive open-ocean deep convection. However, the Maud Rise Polynya generally does not lead to a Weddell Polynya, as was the situation in the September to November of 2017 occurrence of a strong Maud Rise Polynya. Using diverse, long- term observation and reanalysis data, we found that a combination of weakly stratifed ocean near Maud Rise and a wind induced spin-up of the cyclonic Weddell Gyre played a crucial role in generating the 2017 Maud Rise Polynya. More specifcally, the enhanced fow over the southwestern fank of Maud Rise intensifed eddy activity, weakening and raising the pycnocline. However, in 2018 the formation of a Weddell Polynya was hindered by relatively low surface salinity associated with the positive Southern Annular Mode, in contrast to the 1970s’ condition of a prolonged, negative Southern Annular Mode that induced a saltier surface layer and weaker pycnocline. In the Southern Ocean there are two modes in which surface water can attain sufcient density to descend into the deep ocean1. -
Weddell Sea Phytoplankton Blooms Modulated by Sea Ice Variability and Polynya Formation
UC San Diego UC San Diego Previously Published Works Title Weddell Sea Phytoplankton Blooms Modulated by Sea Ice Variability and Polynya Formation Permalink https://escholarship.org/uc/item/7p92z0dm Journal GEOPHYSICAL RESEARCH LETTERS, 47(11) ISSN 0094-8276 Authors VonBerg, Lauren Prend, Channing J Campbell, Ethan C et al. Publication Date 2020-06-16 DOI 10.1029/2020GL087954 Peer reviewed eScholarship.org Powered by the California Digital Library University of California RESEARCH LETTER Weddell Sea Phytoplankton Blooms Modulated by Sea Ice 10.1029/2020GL087954 Variability and Polynya Formation Key Points: Lauren vonBerg1, Channing J. Prend2 , Ethan C. Campbell3 , Matthew R. Mazloff2 , • Autonomous float observations 2 2 are used to characterize the Lynne D. Talley , and Sarah T. Gille evolution and vertical structure of 1 2 phytoplankton blooms in the Department of Computer Science, Princeton University, Princeton, NJ, USA, Scripps Institution of Oceanography, Weddell Sea University of California, San Diego, La Jolla, CA, USA, 3School of Oceanography, University of Washington, Seattle, • Bloom duration and total carbon WA, USA export were enhanced by widespread early ice retreat and Maud Rise polynya formation in 2017 Abstract Seasonal sea ice retreat is known to stimulate Southern Ocean phytoplankton blooms, but • Early spring bloom initiation depth-resolved observations of their evolution are scarce. Autonomous float measurements collected from creates conditions for a 2015–2019 in the eastern Weddell Sea show that spring bloom initiation is closely linked to sea ice retreat distinguishable subsurface fall bloom associated with mixed-layer timing. The appearance and persistence of a rare open-ocean polynya over the Maud Rise seamount in deepening 2017 led to an early bloom and high annual net community production. -
Observing Tracers and the Carbon Cycle
OBSERVING TRACERS AND THE CARBON CYCLE Rana A. FINE1 and Liliane MERLIVAT2 and co-authors3 1Rosenstiel School, University of Miami, Miami, FL 33149, USA 2L.O.D.Y.C., Laboratoire d'Oceanographie Dynamique et de Climatologie, Universite Pierre et Marie Currie, Paris, France 3See footnote ABSTRACT - A program for repeated sampling of tracers and variables essential for quantitative understanding of the carbon cycle is recommended within CLIVAR/GOOS. The program is critical to our monitoring and understanding of climate change both natural and anthropogenic. The objectives are: the quantification of changes in the rates and spatial patterns of oceanic carbon uptake, fluxes and storage of anthropogenic CO2, the detection and possible quantification of changes in water mass renewal and mixing rates, and providing a stringent test of the time integration of models natural and anthropogenic climate variabilityc. The strategy is to put in place a global observing network for tracers and CO2 to document the continuing large scale evolution of these fields. hydrographic lines are advocated, although it is realized that there has to be a limit on these observations due to logistical and resource constraints. Thus, there is the need to supplement these observations with time series and autonomous measurements to provide detail in the temporal evolution of the fields. 1. THE OBJECTIVES A program for repeated sampling of tracers and the carbon cycle is recommended within CLIVAR/GOOS. The measurement program presented here is based upon: widespread consensus expressed in various reports that have proceeded this document, cost effectiveness, and obtaining data that are critical to our monitoring and understanding of climate change both natural and anthropogenic. -
Multidecadal Warming and Density Loss in the Deep Weddell Sea, Antarctica
15 NOVEMBER 2020 S T R A S S E T A L . 9863 Multidecadal Warming and Density Loss in the Deep Weddell Sea, Antarctica VOLKER H. STRASS,GERD ROHARDT,TORSTEN KANZOW,MARIO HOPPEMA, AND OLAF BOEBEL Alfred-Wegener-Institut Helmholtz-Zentrum fur€ Polar- und Meeresforschung, Bremerhaven, Germany (Manuscript received 16 April 2020, in final form 10 August 2020) ABSTRACT: The World Ocean is estimated to store more than 90% of the excess energy resulting from man-made greenhouse gas–driven radiative forcing as heat. Uncertainties of this estimate are related to undersampling of the subpolar and polar regions and of the depths below 2000 m. Here we present measurements from the Weddell Sea that cover the whole water column down to the sea floor, taken by the same accurate method at locations revisited every few years since 1989. Our results show widespread warming with similar long-term temperature trends below 700-m depth at all sampling sites. The mean heating rate below 2000 m exceeds that of the global ocean by a factor of about 5. Salinity tends to increase—in contrast to other Southern Ocean regions—at most sites and depths below 700 m, but nowhere strongly enough to fully compensate for the warming effect on seawater density, which hence shows a general decrease. In the top 700 m neither temperature nor salinity shows clear trends. A closer look at the vertical distribution of changes along an ap- proximately zonal and a meridional section across the Weddell Gyre reveals that the strongest vertically coherent warming is observed at the flanks of the gyre over the deep continental slopes and at its northern edge where the gyre connects to the Antarctic Circumpolar Current (ACC). -
Development of a Pan‐Arctic Monitoring Plan for Polar Bears Background Paper
CAFF Monitoring Series Report No. 1 January 2011 DEVELOPMENT OF A PAN‐ARCTIC MONITORING PLAN FOR POLAR BEARS BACKGROUND PAPER Dag Vongraven and Elizabeth Peacock ARCTIC COUNCIL DEVELOPMENT OF A PAN‐ARCTIC MONITORING PLAN FOR POLAR BEARS Acknowledgements BACKGROUND PAPER The Conservation of Arctic Flora and Fauna (CAFF) is a Working Group of the Arctic Council. Author Dag Vongraven Table of Contents CAFF Designated Agencies: Norwegian Polar Institute Foreword • Directorate for Nature Management, Trondheim, Norway Elizabeth Peacock • Environment Canada, Ottawa, Canada US Geological Survey, 1. Introduction Alaska Science Center • Faroese Museum of Natural History, Tórshavn, Faroe Islands (Kingdom of Denmark) 1 1.1 Project objectives 2 • Finnish Ministry of the Environment, Helsinki, Finland Editing and layout 1.2 Definition of monitoring 2 • Icelandic Institute of Natural History, Reykjavik, Iceland Tom Barry 1.3 Adaptive management/implementation 2 • The Ministry of Domestic Affairs, Nature and Environment, Greenland 2. Review of biology and natural history • Russian Federation Ministry of Natural Resources, Moscow, Russia 2.1 Reproductive and vital rates 3 2.2 Movement/migrations 4 • Swedish Environmental Protection Agency, Stockholm, Sweden 2.3 Diet 4 • United States Department of the Interior, Fish and Wildlife Service, Anchorage, Alaska 2.4 Diseases, parasites and pathogens 4 CAFF Permanent Participant Organizations: 3. Polar bear subpopulations • Aleut International Association (AIA) 3.1 Distribution 5 • Arctic Athabaskan Council (AAC) 3.2 Subpopulations/management units 5 • Gwich’in Council International (GCI) 3.3 Presently delineated populations 5 3.3.1 Arctic Basin (AB) 5 • Inuit Circumpolar Conference (ICC) – Greenland, Alaska and Canada 3.3.2 Baffin Bay (BB) 6 • Russian Indigenous Peoples of the North (RAIPON) 3.3.3 Barents Sea (BS) 7 3.3.4 Chukchi Sea (CS) 7 • Saami Council 3.3.5 Davis Strait (DS) 8 This publication should be cited as: 3.3.6 East Greenland (EG) 8 Vongraven, D and Peacock, E. -
Glacial Ocean Circulation and Stratification Explained by Reduced
Glacial ocean circulation and stratification explained by reduced atmospheric temperature Malte F. Jansena,1 aDepartment of the Geophysical Sciences, The University of Chicago, Chicago, IL 60637 Edited by Mark H. Thiemens, University of California, San Diego, La Jolla, CA, and approved November 7, 2016 (received for review June 27, 2016) Earth’s climate has undergone dramatic shifts between glacial and We test the connection between atmospheric temperature interglacial time periods, with high-latitude temperature changes and ocean circulation and stratification changes, using idealized on the order of 5–10 ◦C. These climatic shifts have been asso- numerical simulations, which allow us to isolate the proposed ciated with major rearrangements in the deep ocean circulation mechanism. We use a coupled ocean–sea-ice model, with atmo- and stratification, which have likely played an important role in spheric temperature, winds, and evaporation–precipitation pre- the observed atmospheric carbon dioxide swings by affecting the scribed as boundary conditions (Materials and Methods). The partitioning of carbon between the atmosphere and the ocean. model uses an idealized continental configuration resembling the The mechanisms by which the deep ocean circulation changed, Atlantic and Southern Oceans, where the most elemental circu- however, are still unclear and represent a major challenge to our lation changes have been inferred (3, 5, 6, 12). understanding of glacial climates. This study shows that vari- ous inferred changes in the deep ocean circulation and stratifica- Results tion between glacial and interglacial climates can be interpreted We first focus on the model’s ability to reproduce key features as a direct consequence of atmospheric temperature differences. -
Ice Production in Ross Ice Shelf Polynyas During 2017–2018 from Sentinel–1 SAR Images
remote sensing Article Ice Production in Ross Ice Shelf Polynyas during 2017–2018 from Sentinel–1 SAR Images Liyun Dai 1,2, Hongjie Xie 2,3,* , Stephen F. Ackley 2,3 and Alberto M. Mestas-Nuñez 2,3 1 Key Laboratory of Remote Sensing of Gansu Province, Heihe Remote Sensing Experimental Research Station, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China; [email protected] 2 Laboratory for Remote Sensing and Geoinformatics, Department of Geological Sciences, University of Texas at San Antonio, San Antonio, TX 78249, USA; [email protected] (S.F.A.); [email protected] (A.M.M.-N.) 3 Center for Advanced Measurements in Extreme Environments, University of Texas at San Antonio, San Antonio, TX 78249, USA * Correspondence: [email protected]; Tel.: +1-210-4585445 Received: 21 April 2020; Accepted: 5 May 2020; Published: 7 May 2020 Abstract: High sea ice production (SIP) generates high-salinity water, thus, influencing the global thermohaline circulation. Estimation from passive microwave data and heat flux models have indicated that the Ross Ice Shelf polynya (RISP) may be the highest SIP region in the Southern Oceans. However, the coarse spatial resolution of passive microwave data limited the accuracy of these estimates. The Sentinel-1 Synthetic Aperture Radar dataset with high spatial and temporal resolution provides an unprecedented opportunity to more accurately distinguish both polynya area/extent and occurrence. In this study, the SIPs of RISP and McMurdo Sound polynya (MSP) from 1 March–30 November 2017 and 2018 are calculated based on Sentinel-1 SAR data (for area/extent) and AMSR2 data (for ice thickness).