Sep 2001 - Aug 2007
Massachusetts Institute of Technology / Woods Hole Oceanographic Institution Joint Program
Field of study
- Physical Oceanography
Glacial Lake Outburst Floods (GLOFs) constitute a major threat in glacierized regions. They cause considerable damage to infrastructure and frequently result in the loss of livestock and human lives. Although the frequency and magnitude of GLOFs seem to have increased worldwide in the last decades, there is currently no reliable scientific evidence supporting this claim, largely due to a lack of flood records on timescales that extend beyond gauged river-flow datasets. This issue is particularly pronounced in Patagonia, where 15 GLOFs were documented between 2008 and 2014. During these events, the discharge of Baker river, which drains most of the eastern side of the Northern Patagonian Icefield, increases from 500-1000 m3/sec to >3000 m3/sec, and river water level rises by 4-6 m. This project will investigate changes in GLOF frequency during the late Holocene (the last ~3000 years) by studying flood deposits recorded in the sediments of Baker fjord, and in elevated lakes and peatbogs along Baker river. In addition, sediment traps will be used to study how modern GLOFs are recorded in fjords sediments, in combination with river and fjord monitoring data. The proposed project will combine the expertise of scientists active in sedimentology, glaciology, hydrology, oceanography, geochemistry, paleoclimatology, and environmental history. Ultimately, our results will be used to assess the possible relationships between GLOF frequency and climate variability. https://geologieugent.wordpress.com/expeditions/paleo-glofs/
Even though this is not a formal project from a single funding source, it is the joint effort from several collaborations with colleagues from Oregon, Chile, and Portugal, to further understand the structure and variability of freshwater plumes, at multiple spatio-temporal scales, in eastern boundary currents. Our work has covered the study of river plumes off Oregon, central-southern Chile, and the Iberian Peninsula. Future efforts will (i) include the river plumes from the Benguela Current System and (ii) compare these systems in relation with climate variability and its role on the freshwater input to the coastal ocean.
Research Items (26)
The West Antarctic Peninsula (WAP) is a highly productive marine ecosystem where extended periods of change have been observed in the form of glacier retreat, reduction of sea-ice cover and shifts in marine populations, among others. The physical environment on the shelf is known to be strongly influenced by the Antarctic Circumpolar Current flowing along the shelf slope and carrying warm, nutrient-rich water, by cold waters flooding into the northern Bransfield Strait from the Weddell Sea, by an extensive network of glaciers and ice shelves, and by strong seasonal to inter-annual variability in sea-ice formation and air–sea interactions, with significant modulation by climate modes like El Niño–Southern Oscillation and the Southern Annular Mode. However, significant gaps have remained in understanding the exchange processes between the open ocean and the shelf, the pathways and fate of oceanic water intrusions, the shelf heat and salt budgets, and the long-term evolution of the shelf properties and circulation. Here, we review how recent advances in long-term monitoring programmes, process studies and newly developed numerical models have helped bridge these gaps and set future research challenges for the WAP system. This article is part of the theme issue ‘The marine system of the West Antarctic Peninsula: status and strategy for progress in a region of rapid change’.
Projections of sea level rise due to ice loss from the land to the ocean have been hampered by a lack of understanding of the role the ocean is playing in glacier retreat, including the processes that contribute to the supply of warm water to the ice-ocean interface. Here shipboard, moored, and weather station data collected off Jorge Montt, a rapidly retreating glacier in Patagonia, are analyzed to understand the influence of wind forcing. During summer, synoptic-scale down-fjord wind events enhance an estuarine-like two-layer flow, increasing the inflow of oceanic deep water. During up-fjord wind events, the inflow of deep water is significantly reduced, and a three-layer exchange flow develops. Overall, along-fjord wind forcing is shown to modulate the inflow of warm water to the fjord by a factor of 2.5 The results suggest that local, channelized winds can be an important process modulating warm water supply and melting of tidewater glaciers.
Submarine canyons cutting across the continental shelf can modulate the cross-shelf circulation being effective pathways to bring water from the deep ocean onto the shelf. Here, we use 69 days of moored array observations of temperature and ocean currents collected during the spring of 2013 and winter-spring 2014, as well as shipboard hydrographic surveys and sea-level observations to characterize cold, oxygen-poor and nutrient-rich upwelling events along the Biobio Submarine Canyon (BbC). The BbC is located within the Gulf of Arauco at 36º 50'S in the Central Chilean Coast. The majority of subtidal temperature at 150 m depth is explained by subtidal variability in alongshore currents on the canyon with a lag of less than a day (r2=0.65). Using the vertical displacement of the 10º and 10.5ºC isotherms, we identified nine upwelling events, lasting between 20 hours to 4.5 days, that resulted in vertical isothermal displacements ranging from 29 to 137 m. The upwelled water likely originated below 200 m. Majority of the cooling events were related with strong northwards (opposite Kelvin wave propagation) flow and low pressure at the coast. Most of these low pressure events occur during relatively weak local wind forcing conditions, and were instead related with Coastal Trapped Waves (CTWs) propagating southwards from lower latitudes. These cold, high-nutrient, low-oxygen waters may be further upwelled and advected into the Gulf of Arauco by wind forcing. Thus, canyon upwelling may be a key driver of biological productivity and oxygen conditions in this Gulf.
We present hydrographic and shipboard ADCP data collected during the fall (April/June) and winter (July/August) and moored velocity observations collected from 2001 to early 2002 on the west Antarctic Peninsula (wAP) shelf during the Southern Ocean Global Ecosystems Dynamics (SO GLOBEC) program. In fall, a geostrophically balanced, buoyant current flows southward along the coast. This Antarctic Peninsula Coastal Current (APCC) forms during the ice-free season and extends from Adelaide Island to Alexander Island, although its path inside Marguerite Bay is uncertain. During the fall of 2001, the APCC had a volume transport of and a freshwater transport (relative to a reference salinity of 34.4) of . From early July to late October, the APCC disappears from the coast as the freshwater input from the coast diminishes and sea-ice forms on the shelf. An examination of the relative sizes of the freshwater sources suggests runoff from land and precipitation over the ocean are the primary sources for the APCC.
The contribution of the winds and the topography in the induction of upwelling along the Chilean coastal zone is calculated. The topographic-induced upwelling is estimated taking into account the effect of the meridional changes of the coastline orientation. The wind-induced upwelling was calculated for the austral summer using NSCAT scatterometer data, resulting a total amount of 2.1x106 m3s-1 of water transported offshore for the whole Chilean upwelling zone. It is shown that the topographic effect dominates the wind-induced upwelling in several parts of the Chilean coast, particularly at 23°S (Antofagasta), 25.5°S, 30°S (Coquimbo), 33°S (Valparaíso) and 37°S (Concepción). Antofagasta, Coquimbo, Valparaíso and Concepción are well known zones of intense upwelling. The results show that the topography plays a key role in the results show that the topography plays a key role in the upwelling of the Chilean coast, specially in its northern part.
- Mar 2018
Proglacial fjords are critical conduits for the exchange of heat and freshwater between the ocean and land ice, and their dynamics heavily modulate the rate of retreat of tidewater glaciers. Here, the magnitude, spatial structure, and seasonal evolution of the ocean forcing on the proglacial fjord off a rapidly retreating glacier (Jorge Montt, Patagonia) are characterized using data from multiple shipboard surveys from 2010 to 2016, a multi‐year mooring array, and a weather station. The melting of the glacier is forced by relatively warm (8 to 11°C) waters entering the fjord over a shallow (45 m deep) sill about 20 km from the terminus. This warm subsurface water is renewed every summer from the surface layer of Gulf of Penas, is transported along the 100 km long Baker Channel, and reaches the proglacial fjord in the late austral summer to early fall, where it remains relatively warm until late austral spring. Analysis of the freshwater fractions in the fjord reveals that the total freshwater content has a strong seasonal signal with maximum fractional values in the summer, mostly explained by variability in subglacial discharge from the glacier. The submarine melting fraction has no strong seasonal signal, but is a first order contributor to the freshwater content of the fjord in winter. This seasonal evolution is consistent with idealized theories of meltwater production, and suggests that the seasonal supply of heat is critical to sustain a high mean temperature for melting, but do not directly impact the variability of meltwater production.
The map is available here in 3 different formats: https://doi.org/10.6084/m9.figshare.5285521.v3 We present a bathymetric map of the Baker-Martinez fjord complex (Chile, 48⁰S) constructed from multiple data sets: multibeam echosounder data of Baker channel (Harada et al., 2008) and of Steffen fjord and Baker river delta (Vandekerkhove & Bertrand, 2016), single beam echosounder data of Jorge Montt fjord (Rivera et al., 2012, Moffat, 2014 and additional data from C. Moffat) and individual bathymetry points from two SHOA nautical charts (SHOA, 2001, 2008). The heterogeneous data with distinct spatial resolution was gridded using the kriging method (3.6 arc-second resolution) in Surfer from Golden Software. We intend to update this map when new datasets become available. The deepest basin of Baker channel (73.8°W) reaches depths of 1075 m below sea level (BSL). To the west, the channel has depths ranging from 450 to 750 m BSL. Martinez channel is between 200 and 440 m deep in its eastern part and reaches depths of 535 m BSL to the west. The bullseye effect in Martinez channel is a mere artefact of the gridding procedure as there is only sparse bathymetric data available in that area. The deepest and largest basin (1405 m BSL and approx. 10 km wide) is located in Messier channel. All the channels are flanked by steep slopes (20 – 40°). Transverse ridges are present throughout the fjord complex, creating separated sub-basins (e.g. north of the deepest basin in Messier channel, in the center of Baker channel at 74.35°W). The fjord becomes shallower (200 – 300m BSL) towards its mouth in the Gulf of Penas. This bathymetric map is intended for regional oceanographic and geological research projects. References: Harada, N. and the shipboard scientific party, 2008. MIRAI cruise report MR06-04 Leg 3, Japan Agency for Marine Earth Science and Technology, Yokosuka, 176 pp. Moffat, C., 2014. Wind-driven modulation of warm water supply to a proglacial fjord, Jorge Montt Glacier, Patagonia. Geophysical Research Letters, 41, 1–8. Rivera, A., Koppes, M.N., Bravo, C., Aravena, J.C., 2012. Little Ice Age advance and retreat of Glaciar Jorge Montt, Chilean Patagonia. Climate of the Past, 8, 403–414. SHOA (Servicio Hidrográfico y Oceanográfico de la Armada de Chile), 2001. "Canal Baker y Puertos Adyacentes (Canal Baker)", 6th ed., sheet 9100, 1:200 000, Mercator projection. SHOA (Servicio Hidrográfico y Oceanográfico de la Armada de Chile), 2008. “Acceso Norte a Canal Messier – Boca de Canales a Isla Van Der Meulen”, 2nd ed., sheet 9300, 1:100 000, Mercator projection. Vandekerkhove, E., Bertrand, S., 2016. Expedition report Paleo-GLOFs and HYDROPROX, 13 pp.
Jorge Montt glacier, located in the Patagonian Ice Fields, has undergone an unprecedented retreat during the past century. To study the impact of the meltwater discharge on the microbial community of the downstream fjord, we targeted Bacteria, Archaea and Fungi communities during austral autumn and winter. Our results showed a singular microbial community present in cold and low salinity surface waters during autumn, when a thicker meltwater layer was observed. Meltwater bacterial sequences were related to Cyanobacteria, Proteobacteria, Actinobacteria and Bacteriodetes previously identified in freshwater and cold ecosystems, suggesting the occurrence of microorganisms adapted to live in the extreme conditions of meltwater. For Fungi, representative sequences related to terrestrial and airborne fungal taxa indicated transport of allochthonous Fungi by the meltwater discharge. In contrast, bottom fjord waters from autumn and winter showed representative OTUs related to sequences of marine microorganisms, which is consistent with current models of fjord circulation. We conclude that meltwater can significantly modify the structure of microbial communities and support the development of a major fraction of microorganisms in surface waters of Patagonian fjords. This article is protected by copyright. All rights reserved.
- Aug 2014
We characterize diurnal and semidiurnal temporal variability of the spring and summer near-shore hydrographic structure and circulation in Cartagena Bay, a small open bay in central Chile, and assess the relative role of diurnal wind and semidiurnal tide as forcing mechanisms of that variability. Our results highlight that the relative importance of these forcing mechanisms and the thermal structure can vary over small spatial scales within the bay. The water column at the southern and most wind-sheltered study site within the Bay (CTGN) was stratified all day despite the sea breeze. Throughout the water column, temperature variability at CTGN was strongly associated with the semidiurnal tide. At the northern site (ECIM), which was relatively more exposed to wind forcing, surface layer temperature fluctuations were principally diurnal and tightly associated with diurnal wind variability. The wind effect weakened near the bottom, where temperature variability was also correlated with the semidiurnal tide. At ECIM, we observed a vertically sheared cross-shore current structure, with onshore surface flow and offshore flow at mid-depth during strong winds. The diurnal variability in cross-shore flows matched diurnal variability in winds, suggesting that this vertical circulation could be directly forced by the wind. The diurnal circulation and the spatial differences in thermal structure across the bay are likely to be important for larval dispersal and material transport in and out of the Bay, as well as between near-shore waters and the shoreline.
A number of studies have posited that coastally generated eddies could cool the southeast Pacific Ocean (SEP) by advecting cool, upwelled waters offshore. We examine this mechanism by characterizing the upper-ocean properties of mesoscale eddies in the SEP with a variety of observations and by estimating the surface-layer eddy heat flux divergence with satellite data. Cyclonic and anticyclonic eddies observed during two cruises featured deep positive salinity anomalies along the 26.5 kg m−3isopycnal, indicating that the eddies had likely trapped and transported coastal waters offshore. The cyclonic eddies observed during the cruises were characterized by shoaling isopycnals in the upper 200 m and cool near-surface temperature anomalies, whereas the upper-ocean structure of anticyclonic eddies was more variable. Using a variety of large-scale observations, including Argo float profiles, drifter records, and satellite sea surface temperature fields, we show that, relative to mean conditions, cyclonic eddies are associated with cooler surface temperatures and that anticyclonic eddies are associated with warmer surface temperatures. Within each data set, the mean eddy surface temperature anomalies are small and of approximately equal magnitude but opposite sign. Eddy statistics drawn from satellite altimetry data reveal that cyclonic and anticyclonic eddies occur with similar frequency and have similar average radii in the SEP. A satellite-based estimate of the surface-layer eddy heat flux divergence, while large in coastal regions, is small when averaged over the SEP, suggesting that eddies do not substantially contribute to cooling the surface layer of the SEP.
We have studied the seasonal variability of four turbid river plumes along the central Chilean coast using daily, high-resolution images of surface turbidity from MODIS (Moderate Resolution Imaging Spectroradiometer) in combination with measurements of wind, river flow, and hydrographic data. Atmospherically corrected MODIS data reveal strong seasonal variability in the areal extent of plume water, as well as in turbidity levels, which are significantly correlated with seasonality in river discharge. A seasonal climatology of turbid plume patterns shows individual plumes merging into an extensive body of turbid waters attached to the coast during fall (April–June)–winter (July–September) (occurs about 10% of days in fall–winter). During spring (October–December) and summer (January–March), the individual plumes remain distinct and occupy a smaller area close to the coast, when observed (evident on less than 30% of days in spring–summer). In spring–summer most plumes are detected for the northern rivers (Mataquito and Maule). When the plumes merge into a coastal band in fall–winter, a turbid area of more than 1000 km2 is observed in the study area between 34.85°S and 37.15°S. This occurs following peaks in river discharge combined with the effect of strong southward (downwelling-favorable) winds. An analysis of key non-dimensional numbers shows that buoyancy dominates plume dynamics during summer, whereas inertial forcing associated with river outflow is more important in winter near the coast. Farther offshore (> 10 km), the effects of rotation and wind tend to dominate the plume dynamics.
Here, the response of a coastally trapped buoyant plume to downwelling-favorable wind forcing is explored using a simplified two-dimensional numerical model and a prognostic theory for the resulting width, depth, and density anomaly and along-shelf transport of the plume. Consistent with the numerical simulations, the analytical model shows that the wind causes mixing of the plume water and that the forced cross-shelf cir-culation can also generate significant deepening and surface narrowing, as well as increased along-shelf transport. The response is due to a combination of the purely advective process that leads to the steepening of the isopycnals and the entrainment of ambient water into the plume. The advective component depends on the initial plume geometry: plumes that have a large fraction of their total width in contact with the bottom (''bottom trapped'') suffer relatively small depth and width changes compared to plumes that have a large fraction of their total width detached from the bottom (''surface trapped''). Key theoretical parameters are W g /W a , the ratio of the width of the plume detached from the bottom to the width of the plume in contact with it, and the ratio of the wind-generated mixed layer d e to the initial plume depth h p , which determines the amount of water initially entrained into the plume. The model results also show that the cross-shelf circulation can be strongly influenced by the wind-driven response in combination with the geostrophic shear of the plume. The continuous entrainment into the plume, as well as transient events, is also discussed.
- Dec 2011
- AGU Fall Meeting Abstracts
As part of the VAMOS Ocean-Cloud-Atmosphere-Land Study (VOCALS) Regional Experiment, properties of upper-ocean turbulence were measured with a microstructure profiler during ship-based surveys, and a longer time series of turbulent kinetic energy dissipation at 9-m depth was collected from a surface mooring. The ship-based surveys allow examination of vertical mixing and its horizontal and vertical variation. The turbulence data from the mooring allows an assessment of the temporal variability of upper-ocean turbulence in the region and its relation to the surface forcing (wind, waves, and surface heat flux) and to oceanic variability, such as near-inertial waves. These data will be used to characterize upper-ocean turbulence beneath the Southeast Pacific stratus deck, its variability, and its role in setting upper-ocean mean properties.
- Dec 2010
We characterize the response of diurnal-period ocean current variability to the sea breeze using measurements of current velocity taken off the mouth of the Itata River and wind stress collected at Hualpen Point (central Chile) in spring of 2007 and summer of 2006 and 2008. During these three periods, the winds are predominately towards the northeast, following the coastal topography, with the highest variability found in the near-diurnal and synoptic frequency bands. The sea breeze amplitude is intermittent in time and is associated with synoptic-scale variability on the order of three to 15 days, so that the diurnal-period winds (and currents) are enhanced when the alongshore wind (i.e. upwelling-favorable) is strong. The water current variability in the near-diurnal band is significant, explaining up to 40% (spring 2007) of the total current variance in the first 15 m depth.
As part of the VAMOS Ocean-Cloud-Atmosphere-Land Study (VOCALS) Regional Experiment, properties of upper-ocean turbulence were observed with a year-long time series of turbulent kinetic energy dissipation at 9-m depth collected from a surface mooring and with a microstructure profiler during month-long ship-based surveys. In this VOCALS region, a relatively warm, salty surface layer overlays a cool, fresh mode water found at about 200m known as Eastern South Pacific Intermediate Water which in turn overlays the Southeastern Pacific oxygen minimum zone. Local budgets point to the need for cooling and freshening of the surface layer, and vertical mixing between the Eastern Pacific Intermediate Water and the surface layer is a possible mechanism for this. The ship-based surveys allow examination of vertical mixing and its spatial variation near an oceanic mesoscale eddy and provide some insight into the role of vertical mixing in the upper part of the ocean in the stratus cloud region. The turbulence data from the mooring allows an assessment of the temporal variability of upper-ocean turbulence in the region and its relation to the surface forcing (wind, waves, and surface heat flux) and to oceanic variability. These data will be used to provide a preliminary characterization of upper-ocean turbulence beneath the Southeast Pacific stratus deck, its variability, and its role in setting upper-ocean mean properties.
The Southeast Pacific is a region characterized by a persistent stratocumulus cloud deck and a cold sea surface temperature (SST) anomaly that extends far beyond the region of upwelling at the coast. Climate models typically fail to reproduce the observed SST suggesting that oceanic processes which contribute to cooling the region are not adequately resolved by these models. Amongst these processes, earlier studies have suggested that lateral transport of anomalously cold, upwelled waters by eddies played a dominant role in regulating the upper ocean's heat content (and hence SST) of the Southeast Pacific. Here, we use a combination of synoptic ocean data, collected during VOCALS-REX, and moored data to examine the role of eddies and other processes in setting SST in the region. Our findings suggest that rather than advection at the surface, eddies contribute to lowering the upper ocean's heat content by bringing cold, fresh Pacific intermediate layer closer surface and that vertical mixing plays an essential role in maintaining the upper-ocean heat and salt balance in the region.
- Dec 2009
- AGU Fall Meeting
Persistent stratus clouds extend over a broad region off Peru and northern Chile. The determination of the processes that govern the heat budget of the upper ocean and the sea surface temperature (SST) under these stratus has been a challenge, due in large part to the lack of observations in the region and as reflected in the warm bias in model SSTs there. Colbo and Weller (2007) used data from that region, and found that at 20°S, 85°W a one dimensional model initialized using observed temperature and salinity profiles and forced with the observed air-sea fluxes yields a surface layer that rapidly becomes too warm and too salty. We have continued observations in that region and can now better quantify the surface forcing as well as oceanic contributions to the upper ocean heat budget. The warm surface layer overlies a fresher seasonal thermocline, where South Pacific Intermediate Water is found. Mean advection is small but westward propagating eddies provide a dominant contribution to upper ocean velocity variability. The eddies originate from close to the coast, where strong upwelling is observed. In the thermocline cyclonic eddies have a warm, salty core while anticyclonic eddies have a fresh but not cool core. The mixed layer hydrographic property signatures of the eddies are weak, though the eddies do have different mixed layer depth and thermocline structure than the background. We examine the mixed layer heat budget and use in situ and satellite observations to quantify the surface heat flux, the advection of the vertically averaged mixed layer temperature by vertical averaged horizontal velocity (including the eddy flux divergence) and infer the residual, which includes the contributions from vertical mixing, entrainment, and other terms. We will examine the temporal variability in the upper ocean heat budget as the large, slow-moving eddies move past the site and assess the impact of the eddies on the local heat balance.
Hydrographic and current velocity observations collected from March 2001 to February 2003 on the west Antarctic Peninsula shelf as part of the Southern Ocean Global Ecosystems Dynamics program are used to characterize intrusions of Upper Circumpolar DeepWater (UCDW) and Lower Circumpolar DeepWater (LCDW) onto the shelf and Marguerite Bay. UCDW is found on the middle and outer shelf along Marguerite Trough, which connects the shelf break to Marguerite Bay, and at another location farther south. UCDW intrudes in the form of frequent (four per month) and small horizontal scales (4 km) warm eddy-like structures with maximum vertical scales of a few hundred meters. However, no evidence of UCDW intrusions was found in Marguerite Bay. LCDW was found in several deep depressions connected to the shelf break, including Marguerite Trough, forming a tongue of relatively dense water 95 m thick (on average) that reaches into Marguerite Bay through Marguerite Trough. A steady advective-diffusive balance for the LCDW intrusion is used to make an estimation of the average upwelling rate and diffusivity in the deep layer within Marguerite Trough, which suggest the LCDW layer is renewed approximately every six weeks.
The Ocean Reference Station at 20°S, 85°W under the stratus clouds west of northern Chile is being maintained to provide ongoing climate-quality records of surface meteorology; air-sea fluxes of heat, freshwater, and momentum; and of upper ocean temperature, salinity, and velocity variability. The Stratus Ocean Reference Station (ORS Stratus) is supported by the National Oceanic and Atmospheric Administration’s (NOAA) Climate Observation Program. It is recovered and redeployed annually, with cruises that have come between October and December. During the 2008 cruise on the NOAA ship Ronald H. Brown to the ORS Stratus site, the primary activities were recovery of the Stratus 8 WHOI surface mooring that had been deployed in October 2007, deployment of a new (Stratus 9) WHOI surface mooring at that site; in-situ calibration of the buoy meteorological sensors by comparison with instrumentation put on board by staff of the NOAA Earth System Research Laboratory (ESRL); and observations of the stratus clouds and lower atmosphere by NOAA ESRL. A buoy for the Pacific tsunami warning system was also serviced in collaboration with the Hydrographic and Oceanographic Service of the Chilean Navy (SHOA). The DART (Deep-Ocean Assessment and Reporting of Tsunami) carries IMET sensors and subsurface oceanographic instruments. A DART II buoy was deployed north of the STRATUS buoy, by personnel from the National Data Buoy Center (NDBC) Argo floats and drifters were launched, and CTD casts carried out during the cruise. The ORS Stratus buoys are equipped with two Improved Meteorological (IMET) systems, which provide surface wind speed and direction, air temperature, relative humidity, barometric pressure, incoming shortwave radiation, incoming longwave radiation, precipitation rate, and sea surface temperature. Additionally, the Stratus 8 buoy received a partial CO2 detector from the Pacific Marine Environmental Laboratory (PMEL). IMET data are made available in near real time using satellite telemetry. The mooring line carries instruments to measure ocean salinity, temperature, and currents. The ESRL instrumentation used during the 2008 cruise included cloud radar, radiosonde balloons, and sensors for mean and turbulent surface meteorology. Finally, the cruise hosted a teacher participating in NOAA’s Teacher at Sea Program. Funding was provided by the National Oceanic and Atmospheric Administration under Grant No. NA17RJ1223 for the Cooperative Institute for Climate and Ocean Research (CICOR).
The Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Timeseries (HOT) Site (WHOTS), 100 km north of Oahu, Hawaii, is intended to provide long-term, high-quality air-sea fluxes as a part of the NOAA Climate Observation Program. The WHOTS mooring also serves as a coordinated part of the HOT program, contributing to the goals of observing heat, fresh water and chemical fluxes at a site representative of the oligotrophic North Pacific Ocean. The approach is to maintain a surface mooring outfitted for meteorological and oceanographic measurements by successive mooring turnarounds. These observations will be used to investigate air-sea interaction processes related to climate variability. This report documents recovery of the WHOTS-4 mooring and deployment of the fifth mooring (WHOTS-5). Both moorings used Surlyn foam buoys as the surface element and were outfitted with two Air-Sea Interaction Meteorology (ASIMET) systems. Each ASIMET system measures, records, and transmits via Argos satellite the surface meteorological variables necessary to compute air-sea fluxes of heat, moisture and momentum. The upper 155 m of the moorings were outfitted with oceanographic sensors for the measurement of temperature, conductivity and velocity. A pCO2 system was installed on the WHOTS-5 buoy. The WHOTS mooring turnaround was done between 3 and 11 June 2008. Operations began with deployment of the WHOTS-5 mooring. This was followed by meteorological intercomparisons and CTDs at the WHOTS-4 site. A period of calmer weather was taken advantage of to recover WHOTS-4 on 6 June 2008. The Kilo Moana then returned to the WHOTS-5 mooring for CTD operations and meteorological intercomparisons. This report describes these cruise operations, as well as some of the in-port operations and pre-cruise buoy preparations.
Observations of current velocity, temperature, salinity and pressure from a 2-year moored array deployment and four hydrographic cruises conducted by the United States Southern Ocean GLOBEC program on the western Antarctic Peninsula continental shelf are used to characterize the ocean circulation and its connection to fresh water and heat fluxes on the shelf. Mean velocities on the shelf are of the order of 5 cm/s or less. Tidal motions are dominated by the M2 and S2 semi-diurnal tides and the 01 and K1 diurnal tides, although the tidal velocities are typically less than 2 cm/s. Near-inertial motions are relatively large, with current velocities as high as 26 cm/s. It is shown that Marguerite Trough, a large bathymetric feature connecting the shelf-break to Marguerite Bay, plays a critical role in determining the circulation. The mean flow is strongly steered in the along-slope direction, and the tidal currents also show increasing current polarization at depth in Marguerite Trough. At time-scales of 5 to 20 days, the observations show bottom-intensified motion in Marguerite Trough consistent with bottom-trapped topographic Rossby waves.
Southern Ocean GLOBal ocean ECosystems As part of the U.S. Southern Ocean GLOBEC program, moored time series measurements of temperature, conductivity (salinity), pressure, velocity, and acoustic backscatter were made from March 2001 to March 2003 in and near Marguerite Bay, located on the Antarctic Peninsula western shelf. To monitor surface forcing during the moored array observations, two automatic weather stations (AWSs) were deployed on islands in Marguerite Bay and time series of wind, air temperature, pressure, and relative humidity were collected from May 2001 through March 2003. This report describes the individual moorings, their locations and local bathymetry, the instrumentation used and measurement depths, calibration and data processing steps taken to produce final time series, and basic plots of the final time series. The AWS data acquisition and processing are also described and basic plots of the final meteorological time series presented. Directions are given about how to access the raw and processed moored and AWS data via the SO GLOBEC website (http://globec.whoi.edu/jg/dir/globec/soglobec/). Funding was provided by the National Science Foundation under contract number OPP-99-10092.
A surface mooring was deployed in the eastern tropical Pacific west of northern Chile from the R/V Melville as part of the Eastern Pacific Investigation of Climate (EPIC). EPIC is a CLIVAR study with the goal of investigating links between sea surface temperature variability in the eastern tropical Pacific and climate over the American continents. Important to that goal is an understanding of the role of clouds in the eastern Pacific in modulating atmosphere-ocean coupling. The mooring was deployed near 20Â°S 85Â°W, at a location near the western edge of the stratocumulus cloud deck found west of Peru and Chile. This deployment started a three-year occupation of that site by a WHOI surface mooring in order to collect accurate time series of surface forcing and upper ocean variability. The surface mooring was deployed by the Upper Ocean Processes Group of the Woods Hole Oceanographic Institution (WHOI). In collaboration with investigators from the University of Concepcion, Concepcion, Chile, an XBT section was made on the way out to the mooring from Arica, Chile, and an XBT and CTD section was made on the way into Arica. The buoy was equipped with meteorological instrumentation, including two Improved METeorological (IMET) systems. The mooring also carried Vector Measuring Current Meters, single-temperature recorders, and conductivity and temperature recorders located in the upper meters of the mooring line. In addition to the instrumentation noted above, a variety of other instruments, including an acoustic current meter, an acoustic doppler current profiler, a bio-optical instrument package, and an acoustic rain guage, were deployed. This report describes, in a general manner, the work that took place and the data collected during the Cook 2 cruise aboard the R/V Melville. The surface mooring deployed during this cruise will be recovered and re-deployed after approximately 12 months and again after 24 months, with a final recovery planned for 36 months after the first setting. Details of the mooring design and preliminary data from the XBT and CTD sections are included. Funding was provided by the National Oceanic and Atmospheric Administration under grant number NA96GP0429.