Conductivity-temperature-depth Research Articles

Marine geological investigation of Edward VIII Gulf, Kemp Coast, East Antarctica

AbstractA physical oceanographic, geophysical and marine geological survey of Edward VIII Gulf, Kemp Coast, collected data from conductivity–temperature–depth casts, multi-beam bathymetric swath mapping and 3.5 kHz sub-bottom surveying. Modified circumpolar deep water (mCDW) is observed in Edward VIII Gulf, as well as notable bathymetric features including mega-scale glacial lineations and a 1750 m-deep trough. Sedimentological, geochemical, rock-magnetic and micropalaeontological analysis of two kasten cores document regional palaeoclimate and palaeo-oceanographic conditions over the past 8000 years, with a warm period occurring fromc.8 to 4 ka and a shift to cooler conditions beginning atc.4 ka and persisting until at least 0.9 ka. Sediment packages > 40 m thick within deep troughs in Edward VIII Gulf present potential targets for higher-resolution Holocene and deglacial climate studies. Despite the presence of mCDW on the shelf, inland bed topography consisting of highland terrain suggests the likelihood of relative stability of this sector of the East Antarctic Ice Sheet.

Monitoring of Discharged Water from Groundwater and Land-based Aquaculture Effluent using CTD Data in Shinyang Bangdu Bay, Jeju Island, Korea

The Sinyang Bangdu Bay in Jeju Island, a semi-inclosed sea, is introduced by the discharged water of the groundwater and land-based aquaculture effluent (LAE) from the surrounding land. To investigate the distribution of the discharged water into the Sinyang Bangdu Bay, 370 Conductivity-Temperature-Depth (CTD) casting data (temperature and salinity) were collected on the nine sampling points from April to September 2019. To understand the spatial and temporal variation of the influent water with changing tide, CTD observation was continuously performed 1-5 times at a 1-hour interval in the daytime. CTD hydrographic data were used the downcast data controlled by constant speed. CTD casting data, water temperature and salinity, were averaged at 0.1 m intervals using the filter mean. The groundwater and LAE in the study area show relatively lower salinity than surrounding waters, and this feature was shown on the west coast in the study area. The both influent waters into the study area had a different spatial influence with changing tidal current. During the flood tide, the west coast of the study area was influenced by the LAE because the discharged water moved to northward along the west coastline of the bay. During the ebb tide, the west coast of the study area was influenced by the groundwater because the discharged water moved southward along the west coastline of the bay. The vertical variation of the discharged water sharply changed within 1 m, and the feature was not observed at more than 1 m wa ter depth.

PROTEVS-MED field experiments: very high resolution hydrographic surveys in the Western Mediterranean Sea

Abstract. From 2015 to 2018 four field experiments (seven legs) were performed in the Western Mediterranean basin during winter or early spring. The main objectives were the assessment of high-resolution modeling and the observation of mesoscale structure and associated ageostrophic dynamics. Thanks to the intensive use of a towed vehicle undulating in the upper oceanic layer between 0 and 400 m depth (SeaSoar), a large number of very high resolution hydrographic transects (total length about 10 000 km) were measured, observing mesoscale dynamics (slope current and its instabilities, anticyclonic eddies, submesoscale coherent vortices, frontal dynamics, convection events, strait outflows) and submesoscale processes like stirring, mixed-layer or symmetric instabilities. When available, the data were completed with velocities recorded by a vessel-mounted acoustic Doppler current profiler (VMADCP) and by surface salinity and temperature recorded by a thermosalinograph (TSG). Classical full-depth CTD (conductivity, temperature, depth) stations were also used, providing the background hydrography of the deeper layers when focusing on peculiar structures. In 2017, a free-fall profiler (MVP-200; MVP – moving vessel profiler) was deployed to manage even higher horizontal resolutions. In 2018, another free-fall profiler (a rapidCAST) was tested. When available, biological sensors (chlorophyll a, turbidity, dissolved oxygen, etc.) were used. They provided useful complementary observations about the circulation. This dataset is an unprecedented opportunity to investigate the very fine scale processes, as the Mediterranean Sea is known for its intense and contrasting dynamics. It should be useful for modellers (who reduce the grid size below a few hundred meters) and should properly resolve finer-scale dynamics. Likewise, theoretical work could also be illustrated by in situ evidence embedded in this dataset. The data are available through the SEANOE repository at: https://doi.org/10.17882/62352 (Dumas et al., 2018).

Distribution of leptocephali and wintertime hydrographic structure in the Kuroshio Extension and northern subtropical gyre

A wintertime net sampling and hydrographic survey was conducted in the Kuroshio Extension (KE) and northern subtropical gyre during 3 cruise-legs in January–March 2006. Conductivity-Temperature-Depth (CTD), expendable CTD (XCTD) and expendable bathythermograph (XBT) surveys were conducted to examine the regional hydrographic structure, which included a distinct KE front water mass boundary, low-salinity subsurface intrusions under and north of the KE current jet, and a deeply mixed anticyclonic recirculation zone south of the current. Large mouth-opening trawl deployments at 36 stations to the north, within and south of the KE collected 1315 leptocephalus larvae, which included ~51 eel and elopomorph fish species. Leptocephali were most abundant/diverse at the southernmost stations at ~25–29°N (29 species), to a lesser extent in the northwestern KE and southern area (27 species), but they were not abundant in the current jet or northernmost areas. Congrid leptocephali were most abundant/diverse (~15 species), with 2 Gnathophis species being most abundant, followed by Ariosoma sp. 7, Ariosoma sp. 4, and Bathycongrus. Smaller numbers of the Nettastomatidae (Saurenchelys stylurus), Muraenidae (12 species), Synaphobranchidae, Chlopsidae (7 species), Nemichthyidae (Nemichthys spp.), Serrivomeridae and a few other families were also collected. Most leptocephali were >50 mm in length for non-mesopelagic eel taxa, because they likely originated from summer–fall spawning and had been transported offshore by the Kuroshio into recirculation areas and farther south possibly by a combination of gyre recirculation and eastward countercurrents. Although the exact transport scenarios of the larvae of the present study cannot be determined, it is possible that some species that spawn along the western margin of the subtropical gyre may use Kuroshio recirculation areas and the wider subtropical gyre as larval development areas by drifting within gyre recirculation before eventually swimming westward to their recruitment areas.

Analysis of Influence of Impedance Matching on Signal Transmission Through Long Wires of XCTD Profiler

Although expendable conductivity–temperature–depth (XCTD) profiler has been extensively studied, there are relatively few studies on the transmission performance of XCTD channel, which makes it unclear that the signal is affected by the channel in the long-distance transmission process. First, the structure of the XCTD is analyzed. Then, according to the working mode and channel structure characteristics of XCTD, the circuit model of the transmission channel is established. In order to better study the channel compensation method, a laboratory transmission system of XCTD is built. By analyzing the influence of channel impedance parameters on the transmission signal, the channel model of XCTD is optimized, and the compensation channel is determined to be series inductance. Finally, the bit error rate (BER) of unoptimized and optimized channels is compared based on ASK and differential phase-shift keying (DPSK) modulation. It is verified that the optimized channel model of XCTD has a certain significance in reducing the BER of the transmission signal. This article has important theoretical significance and practical application value for the research of transmission signal transmission performance of expendable profiler.

Variation of seawater properties on tidal-scale in the entrance of Padangbai Lombok Strait Indonesia

During Marine Science Summer Course 2017, a continuous 24-h conductivity-temperature-depth (CTD) “yoyo” measurement has been carried out at the entrance of Padangbai Lombok Strait to investigate seawater properties variations on semidiurnal tidal-scale which is dominant in the strait. The SBE CTD 19 plus is equipped with optional sensors such as pH, turbidity and chlorophyll-a derived-fluoro. During 24-h field observation, 15 CTD casts from sea surface to about 60 m depth have been acquired. It is shown that observed seawater properties fluctuate strongly four times a day, following semidiurnal-tide period with two flood-tide and two ebb-tide conditions. During flood-tide, water mass is derived from open strait with colder, saltier, denser and low dissolved oxygen characteristics. In contrast, during ebb-tide, local water mass is recirculated back from the inner bay to the open strait. It is interesting to note that fluctuation of chlorophyll-a indicates a diurnal signal. In addition, fluctuation of pH, turbidity and dissolved oxygen showed a weak semidiurnal signal.

Observation pattern of water mass structure at Jeneberang river estuary

This research is a field study conducted in the estuary Jeneberang river. The estuary, the transitional zone formed between the river environment and the marine environment. In this region, there is the mixing of seawater with fresh water that has its own uniqueness with fluctuating salinity. This research aims to see the pattern of salinity distribution and temperature in the area of Jeneberang estuary on the tide and receding conditions. Data retrieval channeled on the area of Jeneberang estuaries with a distance between points 200 m using the ADCP (Acoustic Doppler Current Profiler) and CTD (Conductivity Temperature Depth) tools. The results showed an increase in salinity at Jeneberang estuary, which was influenced by surface and river bed.

Influence of Atlantic inflow on the freshwater content in the upper layer of the Arctic basin

Inter-decadal changes in the water layer of Atlantic origin and freshwater content (FWC) in the upper 100 m layer were traced jointly to assess the influence of inflows from the Atlantic on FWC changes based on oceanographic observations in the Arctic Basin for the 1960s – 2010s. For this assessment, we used oceanographic data collected at the Arctic and Antarctic Research Institute (AARI) and the International Arctic Research Center (IARC). The AARI data for the decades of 1960s – 1990s were obtained mainly at the North Pole drifting ice camps, in high-latitude aerial surveys in the 1970s, as well as in ship-based expeditions in the 1990s. The IARC database contains oceanographic measurements acquired using modern CTD (Conductivity – Temperature – Depth) systems starting from the 2000s. For the reconstruction of decadal fields of the depths of the upper and lower 0 °С isotherms and FWC in the 0–100 m layer in the periods with a relatively small number of observations (1970s – 1990s), we used a climatic regression method based on the conservativeness of the large-scale structure of water masses in the Arctic Basin. Decadal fields with higher data coverage were built using the DIVAnd algorithm. Both methods showed almost identical results when compared. The results demonstrated that the upper boundary of the Atlantic water (AW) layer, identified with the depth of zero isotherm, raised everywhere by several tens of meters in 1990s – 2010s, when compared to its position before the start of warming in the 1970s. The lower boundary of the AW layer, also determined by the depth of zero isotherm, became deeper. Such displacements of the layer boundaries indicate an increase in the volume of water in the Arctic Basin coming not only through the Fram Strait, but also through the Barents Sea. As a result, the balance of water masses was disturbed and its restoration had to occur due to the reduction of the volume of the upper most dynamic freshened layer. Accordingly, the content of fresh water in this layer should decrease. Our results confirmed that FWC in the 0–100 m layer has decreased to 2 m in the Eurasian part of the Arctic Basin to the west of 180° E in the 1990s. In contrast, the FWC to the east of 180° E and closer to the shores of Alaska and the Canadian archipelago has increased. These opposite tendencies have been intensified in the 2000s and the 2010s. A spatial correlation between distributions of the FWC and the positions of the upper AW boundary over different decades confirms a close relationship between both distributions. The influence of fresh water inflow is manifested as an increase in water storage in the Canadian Basin and the Beaufort Gyre in the 1990s – 2010s. The response of water temperature changes from the tropical Atlantic to the Arctic Basin was traced, suggesting not only the influence of SST at low latitudes on changes in FWC, but indicating the distant tropical impact on Arctic processes.

Eastern Tropical Atlantic Mixed Layer Depth: Assessment of Methods from In Situ Profiles in the Gulf of Guinea from Coastal to High Sea

To assess the eastern Atlantic tropical mixed layer depth (MLD) at 4°W in the Gulf of Guinea, water temperature and density profiles from over five hundred historical observational Conductivity – Temperature - Depth (CTD) data were used. These data, obtained from key oceanographic survey databases covering 60 years (1956 to 2016) were used for a numerical and visual determination of the MLD. The numerical approach consists of the use of the algorithms of three methods; while the visual estimation of the MLD were made on both temperature and density profiles. The numerical approaches were evaluated by comparing their results on the determination of tropical MLD with those of the visual inspections by means of statistical and graphical analysis in order to determine the most suitable method for the determination of MLD in the study area. Our results show that the Boyer Montegut density threshold method (potential density) with the constant criterion Δσ = 0.03 kg.m−3 and a reference depth of ten meters is the most appropriate for determining the MLD in the Gulf of Guinea regardless the season. However, in the situation where only temperature profiles are available it is advisable to estimate MLD using the Lorbacher curvative method.

Environmental factors influencing benthic communities in the oxygen minimum zones on the Angolan and Namibian margins

Abstract. Thriving benthic communities were observed in the oxygen minimum zones along the southwestern African margin. On the Namibian margin, fossil cold-water coral mounds were overgrown by sponges and bryozoans, while the Angolan margin was characterized by cold-water coral mounds covered by a living coral reef. To explore why benthic communities differ in both areas, present-day environmental conditions were assessed, using conductivity–temperature–depth (CTD) transects and bottom landers to investigate spatial and temporal variations of environmental properties. Near-bottom measurements recorded low dissolved oxygen concentrations on the Namibian margin of 0–0.15 mL L−1 (≜0 %–9 % saturation) and on the Angolan margin of 0.5–1.5 mL L−1 (≜7 %–18 % saturation), which were associated with relatively high temperatures (11.8–13.2 ∘C and 6.4–12.6 ∘C, respectively). Semidiurnal barotropic tides were found to interact with the margin topography producing internal waves. These tidal movements deliver water with more suitable characteristics to the benthic communities from below and above the zone of low oxygen. Concurrently, the delivery of a high quantity and quality of organic matter was observed, being an important food source for the benthic fauna. On the Namibian margin, organic matter originated directly from the surface productive zone, whereas on the Angolan margin the geochemical signature of organic matter suggested an additional mechanism of food supply. A nepheloid layer observed above the cold-water corals may constitute a reservoir of organic matter, facilitating a constant supply of food particles by tidal mixing. Our data suggest that the benthic fauna on the Namibian margin, as well as the cold-water coral communities on the Angolan margin, may compensate for unfavorable conditions of low oxygen levels and high temperatures with enhanced availability of food, while anoxic conditions on the Namibian margin are at present a limiting factor for cold-water coral growth. This study provides an example of how benthic ecosystems cope with such extreme environmental conditions since it is expected that oxygen minimum zones will expand in the future due to anthropogenic activities.

Thermal Lag Correction From a GLIDER Payload CTD for Poor Temperature Data

This paper describes the thermal lag correction for Glider Payload Conductivity Temperature Depth Profiler data with a poor sampling rate. In particular, the thermal lag correction is more vulnerable to the influence of temperature data. According to variations in salinity with depth and the vertical downcast speed of the glider, salinity data are divided into five parts, and a method based on Morison et al. is proposed to determine the correction parameters. At 40–94 dbar and 140–280 dbar, the salinity difference is dominated by the temperature difference. At 94–140 dbar, the salinity difference is immune to the temperature difference and has a greater influence on the thermal lag-induced salinity error correction. After the sectional correction, the accuracy of the typical salinity interval is upgraded from 0.011 to 0.006 psu, which shows the effectiveness of this sectional method on correcting temperature difference.

Circulation and Heat Flux along the Western Boundary of the North Pacific

On the basis of the conductivity temperature depth (CTD) observation data off the coast of the Philippines (7.5˚–18˚N, 130˚E–the east coast of the Philippines) in the fall of 2005, the water mass distribution, geostrophic flow field, and heat budget are examined. Four water masses are present: the North Pacific Tropical Surface Water, the North Pacific Sub-surface Water, the North Pacific Intermediate Water, and the Antarctic Intermediate Water (AAIW). The previous three corresponded with the North Equatorial Current (NEC), the Kuroshio Current (KC), and the Mindanao Current (MC), respectively. AAIW is the source of the Mindanao Undercurrent. The mass transport of NEC, KC, and MC is 58.7, 15, and 27.95 Sv, respectively (relative to 1500 db). NEC can be balanced by the transport across the whole transect 18˚N (31.81 Sv) and 7.5˚N (26.11 Sv) but not simply by KC and MC. Direct calculation is used to study the heat flux. In sum, 1.45 PW heat is transported outwards the observed region, which is much more than that released from the ocean to the air at the surface (0.05 PW). The net heat lost decreased the water temperature by 0.75℃ each month on average, and the trend agreed well with the SST change. Vertically, the heat transported by the currents is mainly completed in the upper 500 m.

Comparison of the forecasting results of Black Sea surface temperature obtained in the FSBSI MHI and Copernicus marine environment monitoring service

The paper considers the matters of numerical modelling and forecast estimation accu-racy of sea surface temperature in the two monitoring and forecasting centers of the Black Sea – in Federal State Budget Scientific Institution «Marine Hydrophysical Institute of RAS» (FSBSI MHI) and Copernicus marine environment monitoring service. The CTD (Conductivity Temper-ature Depth) profiling data of in situ measurements from research vessel “Professor Vod-yanitskiy” were used to solve the problem. Spatial and temporal mismatch between the model data and in situ measurements was eliminated to form a joint sample of these two data sources. Comparison was performed for the time period from October 2017 to September 2018 and showed that the forecasting results of sea water temperature in FSBSI MHI are more reliable than in Copernicus marine service for all forecast terms.

Observations of oceanic fronts and water-mass properties in the central Japan Sea: Repeated surveys from an underwater glider

Abstract Repeated glider surveys were conducted in the Japan Sea during April–June 2016. Observations revealed mesoscale hydrographic structures of the subpolar front, the Tsushima Warm Current, and eddies formed around flows in the central Japan Sea off Sado Island, in addition to fine-scale water properties associated with mesoscale variation. Data collected from satellite altimeters and thermometers, profiling floats, and ship conductivity–temperature–depth profiles were also analyzed to elucidate spatiotemporal characteristics in multiscale phenomena: mesoscale to fine scale. We present new quantitative estimates of the geostrophic volume transports of the Tsushima Warm Current and the subpolar front current in the central Japan Sea, based on hydrographic data from the glider's transects: they are, respectively, 2.5–2.7 Sv and 1.1–1.4 Sv. The mesoscale frontal/eddy structures varied greatly on a timescale of less than one month. We classified water masses, which revealed that the upper-layer, the low-salinity water within an anticyclonic eddy, was characterized in terms of salinity 100 m in this region, for which there are few hydrographic measurement data.

A novel estimation method for SPM in China eastern coastal waters based on conventional hydrological profile measurements

Suspended particulate matter concentration (SPM) in coastal waters is of great importance for studying sediment resuspension and sediment transportation, especially for the profile distribution in bodies of water. The traditional SPM profile-obtaining method that uses a turbidity meter introduces large uncertainty for pigment particle-dominated waters. This research used a large amount of profile data on optical properties and hydrological measurements parameters (conductivity-temperature-depth (CTD), chlorophyll and turbidity), which were measured synchronously in the Bohai Sea and Yellow Sea; the data were used to analyze the relationships between the vertical distribution of the particulate backscattering ratio and the vertical distribution of pycnocline, chlorophyll and turbidity and to distinguish pigment particles and sediment particles in the vertical distribution. After considering the particle types, we also developed a novel method that exclusively depended on conventional hydrological measurements. The results show that the new method is simplified and effective and could significantly improve the accuracy of SPM estimations in coastal waters.

The Value of Sustained Ocean Observations for Sea Ice Predictions in the Barents Sea

ABSTRACT Dynamical prediction systems have shown potential to meet the emerging need for seasonal forecasts of regional Arctic sea ice. Observationally constrained initial conditions are a key source of skill for these predictions, but the direct influence of different observation types on prediction skill has not yet been systematically investigated. In this work, we perform a hierarchy of observing system experiments with a coupled global data assimilation and prediction system to assess the value of different classes of oceanic and atmospheric observations for seasonal sea ice predictions in the Barents Sea. We find notable skill improvements due to the inclusion of both sea surface temperature (SST) satellite observations and subsurface conductivity–temperature–depth (CTD) measurements. The SST data are found to provide the crucial source of interannual variability, whereas the CTD data primarily provide climatological and trend improvements. Analysis of the Barents Sea ocean heat budget suggests that ocean heat content anomalies in this region are driven by surface heat fluxes on seasonal time scales.

High Resolution Monitoring of Seawater Intrusion in a Multi-Aquifer System-Implementation of a New Downhole Geophysical Tool

Monitoring of seawater intrusion is extremely important for the management of coastal aquifers, and therefore requires reliable and high-frequency monitoring tools. This paper describes the use of a new near field and downhole geophysical tool that monitors seawater intrusion in boreholes with high vertical resolution. This sensor is further used to study the impact of pumping on water electrical conductivity profiles (ECP) at the fresh-saline water interface. The new device was installed in a confined calcareous sandstone aquifer along the northern Israeli coast. The site includes two monitoring wells and one pumping well located at distances of 50, 75 and 125 m from shoreline, respectively. The new geophysical tool, called the subsurface monitoring device (SMD), was examined and compared to water an electric conductivity profiler (ECP) and a conductivity temperature depth (CTD) driver’s data. All methods show similar salinity trends, and changes in pumping regime were clearly identified with both the SMD and CTD. The advantage of using the SMD tool is the high temporal and spatial resolution measurement, which is transferred via internet and can be analyzed and interpreted in real time. Another advantage of the SMD is that it measures the electrical resistivity of the aquifer mostly outside the well, while both water ECP and the CTD measure in-well electrical conductivity; therefore, are subjected to the artefact of vertical flow in the well. Accordingly, while the CTD shows an immediate and sharp response when pumping is stopped, the SMD provides a gradual electric conductivity (EC) change, demonstrating that stability is reached just after a few days, which illustrates, more precisely, the hydrological response of the aquifer.

Improved Estuaries Salinity Stratification at Gyeonggi Bay Using Data Assimilation with Finite Volume Coastal Ocean Model (FVCOM)

Gu, B.-H.; Woo, S.-B., and Kim, S.I., 2019. Improved estuaries salinity stratification at Gyeonggi Bay using data assimilation with Finite Volume Coastal Ocean Model (FVCOM). In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 416-420. Coconut Creek (Florida), ISSN 0749-0208.Assimilating salinity data into coastal models is very important and salinity vertical change is an important component to coastal forecasting. The goal of this study is to represent the salinity stratification at Gyeonggi Bay (GGB) in South Korea and to improve the accuracy of the prediction in hydrodynamics via data assimilation. The GGB area is located in the Yellow Sea between Korea and China and is a semi-closed estuary that has a tidal range above 7 m with a tidal flat where salt water and fresh water is mixed. Salinity stratification appears at Yeomha channel in GGB because it has characteristics of high tide and strong river flow. To represent the tidal flat and creek in the GGB in this study, the unstructured grid numerical model called Finite Volume Coastal Ocean Model (FVCOM) is employed. The performance of the model results is validated against the measured tide, current, and salinity at the Yeomha channel. In order to improve the numerical results, the salinity observations from the surface and bottom Conductivity Temperature Depth (CTD) data in the Yeomha channel are assimilated into the model only for the 4-day middle period out of total simulation days of 15. The direct comparison results show the clear effect of data assimilation for salinity stratification along vertical salinity, and the improvement of salinity profile lasts for 1 day after the end of data assimilation. The salinity stratification in the coastal are also improved as the number of observations and/or data assimilation periods is increased. These results are expected to improve the coastal forecasting system over the GGB area when applied the data assimilation scheme in to the forecasting system.

Glider observations of interleaving layers beneath the Kuroshio primary velocity core east of Taiwan and analyses of underlying dynamics

Submesoscale interleaving layers are caused by lateral intrusions of dissimilar water masses in frontal zones, which are significant processes in shaping physical, biogeochemical, and ecological parameters in the ocean. Possible interleaving layers were sometimes observed by ship-based conductivity-temperature-depth (CTD) surveys with coarse spacing between adjacent stations in the Kuroshio region east of Taiwan but have never been examined dynamically. Here we show the characteristics of interleaving layers observed by a Seaglider with two repeated hydrographic surveys along a triangle track east of Taiwan from December 2016 to March 2017. Salinity profiles indicate that prominent interleaving layers appeared in the intermediate layer (approximately 500–800 m) with vertical and horizontal length scales of O(50) m and O(10–100) km, respectively, during our observations. A dipole eddy pair and a relatively large anticyclonic eddy impinged on the Kuroshio during the first and second surveys, respectively, which brought certain impacts on the interleaving motion as the eddy potentially altered the density slope across the Kuroshio. The associated instability analysis and the Turner angle suggest that the double diffusive instability is the primary driving mechanism for the development of interleaving layers.

Global thermosteric sea level change contributed by the deep ocean below 2000 m estimated by Argo and CTD data

Due to an insufficient amount of observational data, little is known about the temperature variation in the global abyssal ocean and its contribution to sea level change. In this study, we estimated the monthly seawater temperature below 2000 m from 2005–2015 by combining Array for Real-time Geostrophic Oceanography (Argo) and conductivity-temperature-depth (CTD) data. For this purpose, we divided the global ocean into 38 regions according to the CTD temperature profile properties. For each region, we used CTD data to construct a mathematical model to describe the relation of temperatures between 1000–2000 m and those below 2000 m. We then used this mathematical model and the Argo data to reconstruct the temperature profile below 2000 m and evaluate its thermostatic contribution to sea level change. We discovered that the deep ocean below 2000 m contributed 0.12 ± 0.03 mm/yr to the mean global thermosteric sea level rise from 2005–2015. Our result was confirmed by geodetic observations, i.e., the rate of thermosteric sea level rise calculated using altimeter, Gravity Recovery and Climate Experiment (GRACE), and Argo data was approximately 0.15 ± 0.41 mm/yr. The contribution of each ocean layer generally decreased with depth, and there was an obvious fluctuation between approximately 4000–5000 m, interpreted as being caused by geothermal heating of the ocean floor.