Actual Sea Surface Temperature Research Articles

Mechanistic Insights Into Molecular Proxies Through Comparison of Subannually Resolved Sedimentary Records With Instrumental Water Column Data in the Santa Barbara Basin, Southern California

AbstractLipid biomarkers archived in marine sediments include widely applied proxies to reconstruct sea surface temperature (SST). Two prominent groups of SST sensitive biomarkers are long‐chain alkenones from haptophyte algae and glycerol dibiphytanyl glycerol tetraethers (GDGTs) from planktonic Thaumarchaeota. The corresponding proxies, and TEX86, respectively, are strongly correlated with mean annual SST. However, culture experiments suggest that other factors such as nutrients could also influence the proxy signals. We created monthly resolved records of molecular SST proxies via mass spectrometry imaging at 200‐μm resolution in varved sediments from Santa Barbara Basin deposited between 1984 and 2009. Direct comparison to coeval water column data determined at seasonal resolution allows new mechanistic insights into environmental parameters influencing proxy signal formation. The responds sensitively to SST variations, while also being influenced by seasonal variations in nutrient concentrations. Surface water nitrate concentrations above or below ~2 μmol/L are associated with values that overestimate or underestimate actual SST, respectively. Distributions of the two major GDGTs, expressed as the Crenarchaeol‐Caldarchaeol‐Tetraether index (CCaT), are highly similar to those of the minor cycloalkylated compounds GDGT‐1 to GDGT‐3, presented as the corresponding ring index. The CCaT is correlated with subsurface chemical properties, which are controlled by interannual variations in upwelling intensity linked to dynamics of the California Current System. This relationship is attributed to the impact of nutrients on thaumarchaeal growth rates and GDGT cyclization. The coupling of CCaT to SST was weak but enhanced for temperatures averaged across the upper 100 m of the water column.

Skillful Decadal Prediction of Droughts Over Large‐Scale River Basins Across the Globe

AbstractLong‐term droughts, closely linked to oceanic climate variability, are a great threat to the global economy, as well as food and water security. Skillful predictions will provide enormous benefit to the human societies. By taking advantages of the newly available decadal hindcasts and target experiments from the Coupled Model Intercomparison Project phase 6 (CMIP6), this paper evaluates potential predictability and decadal prediction skill of droughts over major river basins across the globe. The results show that the CMIP6 drought prediction is skillful within 3–6 years, and the skill score is 11% higher than CMIP5 over 47% river basins. Prediction skill is enhanced by 15% (16%) over 47% (49%) basins, forced by the actual sea surface temperature over tropical eastern Pacific (North Atlantic). Our findings imply the possibility of drought adaptation based on skillful decadal prediction with sufficient lead time.

전이함수모형에 의한 여수연안 표면수온 예측

In this study, single-input transfer function model is applied to forecast monthly mean sea surface temperature(SST) in 2010 at Yeosu in Korean coastal waters. As input series, monthly mean air temperature series for ten years(2000-2009) at Yeosu in Korea is used, and Monthly mean SST at Yeosu station in Korean coastal waters is used as output series(the same period of input). To build transfer function model, first, input time series is prewhitened, and then cross-correlation functions between prewhitened input and output series are determined. The cross-correlation functions have just two significant values at time lag at 0 and 1. The lag between input and output series, the order of denominator and the order of numerator of transfer function, (b, r, s) are identified as (0, 1, 0). The selected transfer function model shows that there does not exist the lag between monthly mean air temperature and monthly mean SST, and that transfer function has a first-order autoregressive component for monthly mean SST, and that noise model was identified as . The forecasted values by the selected transfer function model are generally higher than actual SST in 2010 and have 6.4 % mean absolute percentage error(MAPE). The error is 2 % lower than MAPE by ARIMA model. This implies that transfer function model could be more available than ARIMA model in terms of forecasting performance of SST.

Investigation of sea surface temperature changes from replicated coral Sr/Ca variations in the eastern equatorial Pacific (Clipperton Atoll) since 1874

Sub-seasonally resolved and replicated coral Sr/Ca time series at Clipperton Atoll (10°18′N, 109°13′W) in the eastern Pacific are assessed as a sea surface temperature (SST) proxy in this region with small seasonal SST variability. The composite coral Sr/Ca time series is a partially replicated record of three live and one sub-modern colony of Porites lobata extending back to 1874. Large inter-colony coral Sr/Ca offsets equate to relative SST differences of 0.6 to 4.3°C and limit the ability to reconstruct absolute SST changes. Moreover, the replication method revealed a 12-year section of growth in one colony where mean Sr/Ca was anomalously low (~1°C higher SST) relative to the other colonies without evidence of diagenesis or other significant skeletal alterations. The presence of this anomalous interval supports the need for multi-coral Sr/Ca replication in specific sites or regions. The Clipperton Composite Sr/Ca anomaly record is significantly coherent (r=0.71–0.76, p<0.001) with gridded instrumental SSTs but with larger amplitude decadal variance that appears to more accurately represent actual SST variability at Clipperton. The amplitude of the secular warming trend during the last century at Clipperton is 0.3 to 0.6°C larger (~twice as large) than the trend in the poorly “ground-truthed” instrumental SST records for the region. The interannual and decadal variability in Clipperton coral Sr/Ca demonstrates strong coherence to the Pacific Decadal Oscillation and the El Niño/Southern Oscillation (ENSO) with reduced ENSO variability from 1920 to late 1930s and enhanced variability in the late twentieth century.

Extension of Vicarious Cold Calibration to 85–92 GHz for Spaceborne Microwave Radiometers

Vicarious cold calibration in the frequency range of 85-92 GHz is analyzed. Vicarious cold calibration cannot be applied at these frequencies as easily as at lower frequencies due to greater sensitivity to water vapor and hydrometeor scattering. The effects of that sensitivity are mitigated by selective filtering of the high-frequency brightness temperatures (TBs) to remove those data where large amounts of water vapor and/or hydrometeor scattering are present. Potential filtering algorithms are presented, and the performance of each with respect to vicarious cold calibration TB stability is characterized. A scattering-based precipitation filter that utilizes a combination of both the lower frequencies from 19 to 37 GHz and the frequencies from 85 to 92 GHz is shown to be the most effective and easily implemented filter. For horizontal polarization, the theoretical minimum TB at the higher frequencies occurs at an unphysically high sea surface temperature (SST), which makes the vicarious cold statistic more sensitive to the population of actual SST values as well as the higher amounts of water vapor associated with warm SSTs. The statistic is stabilized in this case by considering the difference between observed and simulated vicarious cold TBs. Intercalibration between two radiometers using the vicarious cold calibration double difference method at high frequencies is shown to be greatly improved when using the precipitation filter.

Assessing the potential for tropical cyclone induced sea surface cooling to reduce thermal stress on the world's coral reefs

[1] Coral reefs face an uncertain future as rising sea surface temperature (SST) continues to lead to increasingly frequent and intense mass bleaching. At broad spatial scales, tropical cyclone (TC) induced cooling of the upper ocean (SST drops up to 6° C persisting for weeks) reduces thermal stress and accelerates recovery of bleached corals - yet the global prevalence and spatial distribution of this effect remains undocumented and unquantified. A global dataset (1985–2009) of TC wind exposure was constructed and examined against existing thermal stress data to address this. Significant correlations were found between TC activity and the severity of thermal stress at various spatial scales, particularly for Caribbean reefs. From this, it is apparent that TCs play a role in bleaching dynamics at a global scale. However, the prevalence and distribution of this interaction varies by region and requires further examination at finer spatial and temporal scales using actual SST data.

IMPACT OF THE ACTUAL SEA SURFACE TEMPERATURE OF TOKYO BAY ON URBAN AIR TEMPERATURE

To investigate the impact of the actual sea surface temperature (SST) of Tokyo Bay on urban air temperature, an observation network was constructed. SST had been measured at 14 observation sites, such as the lighted buoy in Tokyo Bay since November 2006 to September 2007, and urban air temperature was simulated using the numerical modeling system, WRF, in which SST obtained from this observation was used. In this study, the following results are obtained.(1) From observational study, spatial distribution of air temperature is similar to that of SST, and air temperature over Tokyo Bay is considerably affected by air advection from the coastal land area.(2) Actual SST of Tokyo Bay has significant seasonal and diurnal variation compared with outer SST.(3) Air temperature at Tokyo increases about 0.1°C in summer if the outer SST is replaced with observed SST in Tokyo Bay in the numerical simulation.

Application of the Ensemble Kalman Filter and Smoother to a Coupled Atmosphere-ocean Model

We report an application of the ensemble Kalman filter (EnKF) and smoother (EnKS) to an intermediate coupled atmosphere-ocean model of Zebiak and Cane, into which the sea surface height (SSH) anomaly observations by TOPEX/POSEIDON (T/P) altimetry are assimilated. Smoothed estimates of the 54,403 dimensional state are obtained from 1,981 observational points with 2,048 ensemble members. While assimilated data are SSH anomalies alone, the estimated sea surface temperature (SST) anomalies reproduce primary temporal characteristics of the actual SST. The smoothed estimate of the zonal wind anomalies is also consistent with the observation except for the westerly anomalies in the western Pacific.

Effect of sea surface temperature configuration on model simulations of “equable” climate in the Early Eocene

A major challenge in paleoclimate modeling studies is reproducing the “equable” climate conditions recorded by proxy climate data. This challenge has long been a focus in studies of Eocene paleoclimate. Climate models consistently overestimate mean annual temperature range (MATR) relative to proxy data interpretations and produce minimum temperatures that are far lower than proxy estimates. We hypothesize that the lack of accurate sea surface temperatures (SSTs) and a complete annual cycle definition is responsible for some of these model-data discrepancies in Eocene comparisons. To test this hypothesis, we developed two Eocene annual cycle SST data sets as boundary conditions for model experiments and ran full annual cycle and abbreviated cycle (perpetual) cases. When a perpetual case is replaced by a full annual cycle of SST values, the January 0°C isotherm (freezeline) over North America shifts poleward by ∼5° latitude and (MATR is reduced by ∼5°C. A change from one annual SST cycle to another, equally plausible, annual SST cycle results in a further latitudinal migration (∼5°) of the freezeline and another ∼5°C change in continental interior MATR. Overall, the global mean annual and cold month mean temperatures show little sensitivity to the forcing, while MATR shows larger sensitivity in some continental regions. Our results suggest that the annual cycle of SSTs and the actual SST values incorporated into experiments are major sources of the model-data continental temperature discrepancies reported in past paleoclimate modeling studies. We also find that the relatively coarse spatial resolution of the topography incorporated into paleoclimate models is an additional source of the discrepancy.

Carbon pathways and export associated with the southern Benguela upwelling system: a re-appraisal

A network of six NO3-N-driven carbon pathways between the ocean, shelf and sediments was described in a paper published in 1992. A budgetary approach at the annual scale meant that, if three of the pathways were quantified, solutions could be found algebraically for those remaining. The network of pathways in the present study remains unchanged in principle, but in respect of long-term carbon sequestration, there has been a shift in emphasis from ocean to continental shelf. This results from an adjusted estimate for carbon exported seawards of the continental shelf, mainly owing to a re-examination of the typical offshore penetration of upwelling-derived water. Whereas the 1992 paper used a study based on grey-scale contrast, from Meteosat imagery, to designate a region up to and occasionally beyond the 2 000 m isobath where water of upwelling origin was present on a quasi-permanent basis, the present study used actual sea surface temperatures (SSTs) from NOAA imagery and found comparatively little water continental shelf sediments and 4% is lost below the offshore permanent thermocline. The remaining 30% is re-cycled over shorter time-scales within the southern Benguela system.

Variations in the distributions and isotopic composition of alkenones in Black Sea particles and sediments

Concentrations, unsaturation index ( U 37 k ) and isotopic compositions of individual alkenones were measured for samples of suspended particulate organic matter (POM), sediment trap and sedimentary organic matter from the Black Sea. In general, temperatures estimated from U 37 k are lower than actual sea surface temperatures, indicating existing calibrations may not be appropriate for alkenones in the Black Sea. Specifically, there is a lack of agreement among U 37 k values calculated with and without the concentration of the C 37:4 alkenone which lead to significant differences in temperatures estimated using the available calibrations. The more unsaturated alkenones in suspended POM with high water column residence times may be degraded preferentially, resulting in the observed increase with depth of U 37 k values. The σ 13C of individual alkenones in suspended particles decrease with increased unsaturation. However, there is no correlation between temperature inferred from U 37 k and the isotopic composition of individual alkenones. Isotopic compositions of the C 37:4 alkenone are apparently independent of more saturated isomers. Although the overall pattern of the σ 13C of higher molecular weight alkenones (C 38, C 39) with depth in the water column is similar to that of that of the di- and tri-unsaturated C 37 alkenones, isotopic compositions of individual isomers range several permil. Variation in the isotopic compositions of alkenones may be due to differences either in the biological sources for or mechanisms for removal of alkenones in organic matter suspended in the waters of the Black Sea.

Midlatitude Atmosphere–Ocean Interaction during El Niño. Part I: The North Pacific Ocean

Abstract Atmosphere-ocean experiments are experiments are used to investigate the formation of sea surface temperature (SST) anomalies in the North Pacific Ocean during fall and winter of the El Nino year. Experiments in which the NCAR Community Climate Model (CCM) surface fields am used to force a mixed-layer ocean model in the North Pacific (no air-sea feedback) are compared to simulations in which the CCM and North Pacific Ocean model are coupled. Anomalies in the atmosphere and the North Pacific Ocean during El Nino are obtained from the difference between simulations with and without prescribed warm SST anomalies in the tropical Pacific. In both the forced and coupled experiments, the anomaly pattern resembles a composite of the actual SST anomaly field during El Nino: warm SSTs develop along the cost of North America and cold SSTs form in the central Pacific. In the coupled simulations, air-sea interaction results in a 25% to 50% reduction in the magnitude of the SST and mixed-layer depth anomalies ...