Observing climate change trends in ocean biogeochemistry: when and where.

PubMed

Henson, Stephanie A; Beaulieu, Claudie; Lampitt, Richard

2016-04-01

Understanding the influence of anthropogenic forcing on the marine biosphere is a high priority. Climate change-driven trends need to be accurately assessed and detected in a timely manner. As part of the effort towards detection of long-term trends, a network of ocean observatories and time series stations provide high quality data for a number of key parameters, such as pH, oxygen concentration or primary production (PP). Here, we use an ensemble of global coupled climate models to assess the temporal and spatial scales over which observations of eight biogeochemically relevant variables must be made to robustly detect a long-term trend. We find that, as a global average, continuous time series are required for between 14 (pH) and 32 (PP) years to distinguish a climate change trend from natural variability. Regional differences are extensive, with low latitudes and the Arctic generally needing shorter time series (<~30 years) to detect trends than other areas. In addition, we quantify the 'footprint' of existing and planned time series stations, that is the area over which a station is representative of a broader region. Footprints are generally largest for pH and sea surface temperature, but nevertheless the existing network of observatories only represents 9-15% of the global ocean surface. Our results present a quantitative framework for assessing the adequacy of current and future ocean observing networks for detection and monitoring of climate change-driven responses in the marine ecosystem. © 2016 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.

A Reversal of Decadal Trends in the Equatorial and North Indian Ocean

NASA Astrophysics Data System (ADS)

Thompson, P. R.; Merrifield, M. A.; McCreary, J. P., Jr.; Firing, E.; Piecuch, C. G.

2016-02-01

Sea level and upper ocean temperature trends in the Equatorial and North Indian Ocean (ENIO) reversed sign shortly after the turn of the century. The trend reversal is spatially coherent and characterized by subsurface cooling during 1993-2002 followed by subsurface warming during 2003-2012. Here we explore the dynamics and forcing of the decadal trend reversal, with a particular emphasis on the role of the Indian Ocean cross-equatorial cell (CEC) and anomalies transmitted from the Pacific basin to the ENIO via the Indonesian Throughflow (ITF). An examination of reanalysis wind-stress fields suggest that forcing of the CEC is enhanced during the cooling phase of the decadal fluctuation, which may account for the cooling trend below 100m in the ENIO during the first decade. In contrast, the subsurface warming during the second decade occurs at thermocline levels, which suggests a deepening of the thermocline during this period. Enhanced Pacific tradewinds since the early 1990s result in a deepening thermocline in the western tropical Pacific (WTP), which may be transmitted to the Indian Ocean basin via the ITF. We present results from simple model experiments that assess the potential for thermocline anomalies originating in the WTP to account for the deepening thermocline in the ENIO during the warming phase of the decadal fluctuation.

Decadal Variability of Temperature and Salinity in the Northwest Atlantic Ocean

NASA Astrophysics Data System (ADS)

Mishonov, A. V.; Seidov, D.; Reagan, J. R.; Boyer, T.; Parsons, A. R.

2017-12-01

There are only a few regions in the World Ocean where the density of observations collected over the past 60 years is sufficient for reliable data mapping with spatial resolutions finer than one-degree. The Northwest Atlantic basin is one such regions where a spatial resolution of gridded temperature and salinity fields, comparable to those generated by eddy-resolving numerical models of ocean circulation, has recently becomes available. Using the new high-resolution Northwest Atlantic Regional Climatology, built on quarter-degree and one-tenth-degree resolution fields, we analyzed decadal variability and trends of temperature and salinity over 60 years in the Northwest Atlantic, and two 30-year ocean climates of 1955-1984 and 1985-2012 to evaluate the oceanic climate shift in this region. The 30-year climate shift is demonstrated using an innovative 3-D visualization of temperature and salinity. Spatial and temporal variability of heat accumulation found in previous research of the entire North Atlantic Ocean persists in the Northwest Atlantic Ocean. Salinity changes between two 30-year climates were also computed and are discussed.

Decadal trends in Red Sea maximum surface temperature.

PubMed

Chaidez, V; Dreano, D; Agusti, S; Duarte, C M; Hoteit, I

2017-08-15

Ocean warming is a major consequence of climate change, with the surface of the ocean having warmed by 0.11 °C decade -1 over the last 50 years and is estimated to continue to warm by an additional 0.6 - 2.0 °C before the end of the century 1 . However, there is considerable variability in the rates experienced by different ocean regions, so understanding regional trends is important to inform on possible stresses for marine organisms, particularly in warm seas where organisms may be already operating in the high end of their thermal tolerance. Although the Red Sea is one of the warmest ecosystems on earth, its historical warming trends and thermal evolution remain largely understudied. We characterized the Red Sea's thermal regimes at the basin scale, with a focus on the spatial distribution and changes over time of sea surface temperature maxima, using remotely sensed sea surface temperature data from 1982 - 2015. The overall rate of warming for the Red Sea is 0.17 ± 0.07 °C decade -1 , while the northern Red Sea is warming between 0.40 and 0.45 °C decade -1 , all exceeding the global rate. Our findings show that the Red Sea is fast warming, which may in the future challenge its organisms and communities.

Secular trends and climate drift in coupled ocean-atmosphere general circulation models

NASA Astrophysics Data System (ADS)

Covey, Curt; Gleckler, Peter J.; Phillips, Thomas J.; Bader, David C.

2006-02-01

Coupled ocean-atmosphere general circulation models (coupled GCMs) with interactive sea ice are the primary tool for investigating possible future global warming and numerous other issues in climate science. A long-standing problem with such models is that when different components of the physical climate system are linked together, the simulated climate can drift away from observation unless constrained by ad hoc adjustments to interface fluxes. However, 11 modern coupled GCMs, including three that do not employ flux adjustments, behave much better in this respect than the older generation of models. Surface temperature trends in control run simulations (with external climate forcing such as solar brightness and atmospheric carbon dioxide held constant) are small compared with observed trends, which include 20th century climate change due to both anthropogenic and natural factors. Sea ice changes in the models are dominated by interannual variations. Deep ocean temperature and salinity trends are small enough for model control runs to extend over 1000 simulated years or more, but trends in some regions, most notably the Arctic, differ substantially among the models and may be problematic. Methods used to initialize coupled GCMs can mitigate climate drift but cannot eliminate it. Lengthy "spin-ups" of models, made possible by increasing computer power, are one reason for the improvements this paper documents.

Global Ocean Integrals and Means, with Trend Implications.

PubMed

Wunsch, Carl

2016-01-01

Understanding the ocean requires determining and explaining global integrals and equivalent average values of temperature (heat), salinity (freshwater and salt content), sea level, energy, and other properties. Attempts to determine means, integrals, and climatologies have been hindered by thinly and poorly distributed historical observations in a system in which both signals and background noise are spatially very inhomogeneous, leading to potentially large temporal bias errors that must be corrected at the 1% level or better. With the exception of the upper ocean in the current altimetric-Argo era, no clear documentation exists on the best methods for estimating means and their changes for quantities such as heat and freshwater at the levels required for anthropogenic signals. Underestimates of trends are as likely as overestimates; for example, recent inferences that multidecadal oceanic heat uptake has been greatly underestimated are plausible. For new or augmented observing systems, calculating the accuracies and precisions of global, multidecadal sampling densities for the full water column is necessary to avoid the irrecoverable loss of scientifically essential information.

Decadal trends in deep ocean salinity and regional effects on steric sea level

NASA Astrophysics Data System (ADS)

Purkey, S. G.; Llovel, W.

2017-12-01

We present deep (below 2000 m) and abyssal (below 4000 m) global ocean salinity trends from the 1990s through the 2010s and assess the role of deep salinity in local and global sea level budgets. Deep salinity trends are assessed using all deep basins with available full-depth, high-quality hydrographic section data that have been occupied two or more times since the 1980s through either the World Ocean Circulation Experiment (WOCE) Hydrographic Program or the Global Ship-Based Hydrographic Investigations Program (GO-SHIP). All salinity data is calibrated to standard seawater and any intercruise offsets applied. While the global mean deep halosteric contribution to sea level rise is close to zero (-0.017 +/- 0.023 mm/yr below 4000 m), there is a large regional variability with the southern deep basins becoming fresher and northern deep basins becoming more saline. This meridional gradient in the deep salinity trend reflects different mechanisms driving the deep salinity variability. The deep Southern Ocean is freshening owing to a recent increased flux of freshwater to the deep ocean. Outside of the Southern Ocean, the deep salinity and temperature changes are tied to isopycnal heave associated with a falling of deep isopycnals in recent decades. Therefore, regions of the ocean with a deep salinity minimum are experiencing both a halosteric contraction with a thermosteric expansion. While the thermosteric expansion is larger in most cases, in some regions the halosteric compensates for as much as 50% of the deep thermal expansion, making a significant contribution to local sea level rise budgets.

Ocean Bottom Pressure Seasonal Cycles and Decadal Trends from GRACE Release-05: Ocean Circulation Implications

NASA Astrophysics Data System (ADS)

Johnson, G. C.; Chambers, D. P.

2013-12-01

Ocean mass variations are important for diagnosing sea level budgets, the hydrological cycle and global energy budget, as well as ocean circulation variability. Here seasonal cycles and decadal trends of ocean mass from January 2003 to December 2012, both global and regional, are analyzed using GRACE Release 05 data. The trend of global flux of mass into the ocean approaches 2 cm decade-1 in equivalent sea level rise. Regional trends are of similar magnitude, with the North Pacific, South Atlantic, and South Indian oceans generally gaining mass and other regions losing mass. These trends suggest a spin-down of the North Pacific western boundary current extension and the Antarctic Circumpolar Current in the South Atlantic and South Indian oceans. The global average seasonal cycle of ocean mass is about 1 cm in amplitude, with a maximum in early October and volume fluxes in and out of the ocean reaching 0.5 Sv (1 Sv = 1 × 106 m3 s-1) when integrated over the area analyzed here. Regional patterns of seasonal ocean mass change have typical amplitudes of 1-4 cm, and include maxima in the subtropics and minima in the subpolar regions in hemispheric winters. The subtropical mass gains and subpolar mass losses in the winter spin up both subtropical and subpolar gyres, hence the western boundary current extensions. Seasonal variations in these currents are order 10 Sv, but since the associated depth-averaged current variations are only order 0.1 cm s-1, they would be difficult to detect using in situ oceanographic instruments. a) Amplitude (colors, in cm) and b) phase (colors, in months of the year) of an annual harmonic fit to monthly GRACE Release 05 CSR 500 km smoothed maps (concurrently with a trend and the semiannual harmonic). The 97.5% confidence interval for difference from zero is also indicated (solid black line). Data within 300 km of coastlines are not considered.

Decadal trends in Indian Ocean ambient sound.

PubMed

Miksis-Olds, Jennifer L; Bradley, David L; Niu, Xiaoyue Maggie

2013-11-01

The increase of ocean noise documented in the North Pacific has sparked concern on whether the observed increases are a global or regional phenomenon. This work provides evidence of low frequency sound increases in the Indian Ocean. A decade (2002-2012) of recordings made off the island of Diego Garcia, UK in the Indian Ocean was parsed into time series according to frequency band and sound level. Quarterly sound level comparisons between the first and last years were also performed. The combination of time series and temporal comparison analyses over multiple measurement parameters produced results beyond those obtainable from a single parameter analysis. The ocean sound floor has increased over the past decade in the Indian Ocean. Increases were most prominent in recordings made south of Diego Garcia in the 85-105 Hz band. The highest sound level trends differed between the two sides of the island; the highest sound levels decreased in the north and increased in the south. Rate, direction, and magnitude of changes among the multiple parameters supported interpretation of source functions driving the trends. The observed sound floor increases are consistent with concurrent increases in shipping, wind speed, wave height, and blue whale abundance in the Indian Ocean.

Recent summer precipitation trends in the Greater Horn of Africa and the emerging role of Indian Ocean sea surface temperature

NASA Astrophysics Data System (ADS)

Williams, A. Park; Funk, Chris; Michaelsen, Joel; Rauscher, Sara A.; Robertson, Iain; Wils, Tommy H. G.; Koprowski, Marcin; Eshetu, Zewdu; Loader, Neil J.

2012-11-01

We utilize a variety of climate datasets to examine impacts of two mechanisms on precipitation in the Greater Horn of Africa (GHA) during northern-hemisphere summer. First, surface-pressure gradients draw moist air toward the GHA from the tropical Atlantic Ocean and Congo Basin. Variability of the strength of these gradients strongly influences GHA precipitation totals and accounts for important phenomena such as the 1960s-1980s rainfall decline and devastating 1984 drought. Following the 1980s, precipitation variability became increasingly influenced by the southern tropical Indian Ocean (STIO) region. Within this region, increases in sea-surface temperature, evaporation, and precipitation are linked with increased exports of dry mid-tropospheric air from the STIO region toward the GHA. Convergence of dry air above the GHA reduces local convection and precipitation. It also produces a clockwise circulation response near the ground that reduces moisture transports from the Congo Basin. Because precipitation originating in the Congo Basin has a unique isotopic signature, records of moisture transports from the Congo Basin may be preserved in the isotopic composition of annual tree rings in the Ethiopian Highlands. A negative trend in tree-ring oxygen-18 during the past half century suggests a decline in the proportion of precipitation originating from the Congo Basin. This trend may not be part of a natural cycle that will soon rebound because climate models characterize Indian Ocean warming as a principal signature of greenhouse-gas induced climate change. We therefore expect surface warming in the STIO region to continue to negatively impact GHA precipitation during northern-hemisphere summer.

Did hydrographic sampling capture global and regional deep ocean heat content trends accurately between 1990-2010?

NASA Astrophysics Data System (ADS)

Garry, Freya; McDonagh, Elaine; Blaker, Adam; Roberts, Chris; Desbruyères, Damien; King, Brian

2017-04-01

Estimates of heat content change in the deep oceans (below 2000 m) over the last thirty years are obtained from temperature measurements made by hydrographic survey ships. Cruises occupy the same tracks across an ocean basin approximately every 5+ years. Measurements may not be sufficiently frequent in time or space to allow accurate evaluation of total ocean heat content (OHC) and its rate of change. It is widely thought that additional deep ocean sampling will also aid understanding of the mechanisms for OHC change on annual to decadal timescales, including how OHC varies regionally under natural and anthropogenically forced climate change. Here a 0.25˚ ocean model is used to investigate the magnitude of uncertainties and biases that exist in estimates of deep ocean temperature change from hydrographic sections due to their infrequent timing and sparse spatial distribution during 1990 - 2010. Biases in the observational data may be due to lack of spatial coverage (not enough sections covering the basin), lack of data between occupations (typically 5-10 years apart) and due to occupations not closely spanning the time period of interest. Between 1990 - 2010, the modelled biases globally are comparatively small in the abyssal ocean below 3500 m although regionally certain biases in heat flux into the 4000 - 6000 m layer can be up to 0.05 Wm-2. Biases in the heat flux into the deep 2000 - 4000 m layer due to either temporal or spatial sampling uncertainties are typically much larger and can be over 0.1 Wm-2 across an ocean. Overall, 82% of the warming trend below 2000 m is captured by observational-style sampling in the model. However, at 2500 m (too deep for additional temperature information to be inferred from upper ocean Argo) less than two thirds of the magnitude of the global warming trend is obtained, and regionally large biases exist in the Atlantic, Southern and Indian Oceans, highlighting the need for widespread improved deep ocean temperature sampling

Interpreting the Latitudinal Structure of Differences Between Modeled and Observed Temperature Trends (Invited)

NASA Astrophysics Data System (ADS)

Santer, B. D.; Mears, C. A.; Gleckler, P. J.; Solomon, S.; Wigley, T.; Arblaster, J.; Cai, W.; Gillett, N. P.; Ivanova, D. P.; Karl, T. R.; Lanzante, J.; Meehl, G. A.; Stott, P.; Taylor, K. E.; Thorne, P.; Wehner, M. F.; Zou, C.

2010-12-01

We perform the most comprehensive comparison to date of simulated and observed temperature trends. Comparisons are made for different latitude bands, timescales, and temperature variables, using information from a multi-model archive and a variety of observational datasets. Our focus is on temperature changes in the lower troposphere (TLT), the mid- to upper troposphere (TMT), and at the sea surface (SST). For SST, TLT, and TMT, trend comparisons over the satellite era (1979 to 2009) always yield closest agreement in mid-latitudes of the Northern Hemisphere. There are pronounced discrepancies in the tropics and in the Southern Hemisphere: in both regions, the multi-model average warming is consistently larger than observed. At high latitudes in the Northern Hemisphere, the observed tropospheric warming exceeds multi-model average trends. The similarity in the latitudinal structure of this discrepancy pattern across different temperature variables and observational data sets suggests that these trend differences are real, and are not due to residual inhomogeneities in the observations. The interpretation of these results is hampered by the fact that the CMIP-3 multi-model archive analyzed here convolves errors in key external forcings with errors in the model response to forcing. Under a "forcing error" interpretation, model-average temperature trends in the Southern Hemisphere extratropics are biased warm because many models neglect (and/or inaccurately specify) changes in stratospheric ozone and the indirect effects of aerosols. An alternative "response error" explanation for the model trend errors is that there are fundamental problems with model clouds and ocean heat uptake over the Southern Ocean. When SST changes are compared over the longer period 1950 to 2009, there is close agreement between simulated and observed trends poleward of 50°S. This result is difficult to reconcile with the hypothesis that the trend discrepancies over 1979 to 2009 are primarily

Multidecadal-scale adjustment of the ocean mixed layer heat budget in the tropics: examining ocean reanalyses

NASA Astrophysics Data System (ADS)

Cook, Kerry H.; Vizy, Edward K.; Sun, Xiaoming

2018-03-01

Distributions of ocean mixed layer temperature trends and trends in the net heat flux from the atmosphere differ, indicating the important role of the transport of heat within the ocean for determining temperature trends. Annual-mean, linear trends in the components of the tropical ocean mixed layer heat budget for 1980-2015 are diagnosed in 4 ocean reanalyses to improve our physical understanding of multidecadal-scale SST trends. The well-known temperature trend in the tropical Pacific, with cooling in the east and warming in the west, is reproduced in each reanalysis with high statistical significance. Cooling in the east is associated with negative trends in the net heat flux from the atmosphere and enhanced equatorial upwelling related to a strengthening of the subtropical cells. Negative trends in the net heat flux also occur in the western tropical Pacific, but advective warming associated with a strengthening and shoaling of the equatorial undercurrent overwhelms these negative trends. The strengthening of the equatorial undercurrent is consistent with enhanced easterly wind stress, which is applied to the ocean reanalyses, and differential sea level trends that enhance the negative zonal height gradient across the Pacific. The Pacific North Equatorial countercurrent is also strengthening in all 4 reanalyses in association with a strengthening of the sea level trough at 10°N in the central and eastern Pacific. All 4 ocean reanalyses produce warming of 0.1-0.3 K/decade in the North Atlantic with statistical significance levels ranging from below 90-99%. The Atlantic is similar to the Pacific in having the equatorial undercurrent strengthening, but indications of shoaling are less consistent in the reanalyses and the North Equatorial Countercurrent in the Atlantic is not strengthening. Large-scale ocean mixed layer warming trends in the Indian Ocean in the reanalyses are interrupted by some regional cooling close to the equator. Net surface heat flux trends

Trends in Ocean Colour and Chlorophyll Concentration from 1889 to 2000, Worldwide

PubMed Central

Wernand, Marcel R.; van der Woerd, Hendrik J.; Gieskes, Winfried W. C.

2013-01-01

Marine primary productivity is an important agent in the global cycling of carbon dioxide, a major ‘greenhouse gas’, and variations in the concentration of the ocean's phytoplankton biomass can therefore explain trends in the global carbon budget. Since the launch of satellite-mounted sensors globe-wide monitoring of chlorophyll, a phytoplankton biomass proxy, became feasible. Just as satellites, the Forel-Ule (FU) scale record (a hardly explored database of ocean colour) has covered all seas and oceans – but already since 1889. We provide evidence that changes of ocean surface chlorophyll can be reconstructed with confidence from this record. The EcoLight radiative transfer numerical model indicates that the FU index is closely related to chlorophyll concentrations in open ocean regions. The most complete FU record is that of the North Atlantic in terms of coverage over space and in time; this dataset has been used to test the validity of colour changes that can be translated to chlorophyll. The FU and FU-derived chlorophyll data were analysed for monotonously increasing or decreasing trends with the non-parametric Mann-Kendall test, a method to establish the presence of a consistent trend. Our analysis has not revealed a globe-wide trend of increase or decrease in chlorophyll concentration during the past century; ocean regions have apparently responded differentially to changes in meteorological, hydrological and biological conditions at the surface, including potential long-term trends related to global warming. Since 1889, chlorophyll concentrations have decreased in the Indian Ocean and in the Pacific; increased in the Atlantic Ocean, the Mediterranean, the Chinese Sea, and in the seas west and north-west of Japan. This suggests that explanations of chlorophyll changes over long periods should focus on hydrographical and biological characteristics typical of single ocean regions, not on those of ‘the’ ocean. PMID:23776435

Trends in ocean colour and chlorophyll concentration from 1889 to 2000, worldwide.

PubMed

Wernand, Marcel R; van der Woerd, Hendrik J; Gieskes, Winfried W C

2013-01-01

Marine primary productivity is an important agent in the global cycling of carbon dioxide, a major 'greenhouse gas', and variations in the concentration of the ocean's phytoplankton biomass can therefore explain trends in the global carbon budget. Since the launch of satellite-mounted sensors globe-wide monitoring of chlorophyll, a phytoplankton biomass proxy, became feasible. Just as satellites, the Forel-Ule (FU) scale record (a hardly explored database of ocean colour) has covered all seas and oceans--but already since 1889. We provide evidence that changes of ocean surface chlorophyll can be reconstructed with confidence from this record. The EcoLight radiative transfer numerical model indicates that the FU index is closely related to chlorophyll concentrations in open ocean regions. The most complete FU record is that of the North Atlantic in terms of coverage over space and in time; this dataset has been used to test the validity of colour changes that can be translated to chlorophyll. The FU and FU-derived chlorophyll data were analysed for monotonously increasing or decreasing trends with the non-parametric Mann-Kendall test, a method to establish the presence of a consistent trend. Our analysis has not revealed a globe-wide trend of increase or decrease in chlorophyll concentration during the past century; ocean regions have apparently responded differentially to changes in meteorological, hydrological and biological conditions at the surface, including potential long-term trends related to global warming. Since 1889, chlorophyll concentrations have decreased in the Indian Ocean and in the Pacific; increased in the Atlantic Ocean, the Mediterranean, the Chinese Sea, and in the seas west and north-west of Japan. This suggests that explanations of chlorophyll changes over long periods should focus on hydrographical and biological characteristics typical of single ocean regions, not on those of 'the' ocean.

Observed Recent Trends in Tropical Cyclone Rainfall Over Major Ocean Basins

NASA Technical Reports Server (NTRS)

Lau, K. M.; Zhou, Y. P.

2011-01-01

In this study, we use Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Climatology Project (GPCP) rainfall data together with historical storm track records to examine the trend of tropical cyclone (TC) rainfall in major ocean basins during recent decades (1980-2007). We find that accumulated total rainfall along storm tracks for all tropical cyclones shows a weak positive trend over the whole tropics. However, total rainfall associated with weak storms, and intense storms (Category 4-5) both show significant positive trends, while total rainfall associated with intermediate storms (Category1-3) show a significant negative trend. Storm intensity defined as total rain produced per unit storm also shows increasing trend for all storm types. Basin-wide, from the first half (1980-1993) to the second half (1994-2007) of the data period, the North Atlantic shows the pronounced increase in TC number and TC rainfall while the Northeast Pacific shows a significant decrease in all storm types. Except for the Northeast Pacific, all other major basins (North Atlantic, Northwest Pacific, Southern Oceans, and Northern Indian Ocean) show a significant increase in total number and rainfall amount in Category 4-5 storms. Overall, trends in TC rainfall in different ocean basins are consistent with long-term changes in the ambient large-scale environment, including SST, vertical wind shear, sea level pressure, mid-tropospheric humidity, and Maximum Potential Intensity (MPI). Notably the pronounced positive (negative) trend of TC rainfall in the North Atlantic (Northeast Pacific) appears to be related to the most (least) rapid increase in SST and MPI, and the largest decrease (increase) in vertical wind shear in the region, relative to other ocean basins.

Trends in Ocean Irradiance using a Radiative Model Forced with Terra Aerosols and Clouds

NASA Technical Reports Server (NTRS)

Gregg, Watson; Casey, Nancy; Romanou, Anastasia

2010-01-01

Aerosol and cloud information from MODIS on Terra provide enhanced capability to understand surface irradiance over the oceans and its variability. These relationships can be important for ocean biology and carbon cycles. An established radiative transfer model, the Ocean-Atmosphere Spectral Irradiance Model (OASIM) is used to describe ocean irradiance variability on seasonal to decadal time scales. The model is forced with information on aerosols and clouds from the MODIS sensor on Terra and Aqua. A 7-year record (2000-2006) showed no trends in global ocean surface irradiance or photosynthetic available irradiance (PAR). There were significant (P<0.05) negative trends in the Mediterranean Sea, tropical Pacific) and tropical Indian Oceans, of -7.0, -5.0 and -2.7 W/sq m respectively. Global interannual variability was also modest. Regional interannual variability was quite large in some ocean basins, where monthly excursions from climatology were often >20 W/sq m. The trends using MODIS data contrast with results from OASIM using liquid water path estimates from the International Satellite Cloud Climatology Project (ISCCP). Here, a global trend of -2 W/sq m was observed, largely dues to a large negative trend in the Antarctic -12 W/sq m. These results suggest the importance of the choice of liquid water path data sets in assessments of medium-length trends in ocean surface irradiance. The choices also impact the evaluation of changes in ocean biogeochemistry.

Seasonal and elevational contrasts in temperature trends in Central Chile between 1979 and 2015

NASA Astrophysics Data System (ADS)

Burger, F.; Brock, B.; Montecinos, A.

2018-03-01

We analyze trends in temperature from 18 temperature stations and one upper air sounding site at 30°-35° S in central Chile between 1979-2015, to explore geographical and season temperature trends and their controls, using regional ocean-atmosphere indices. Significant warming trends are widespread at inland stations, while trends are non-significant or negative at coastal sites, as found in previous studies. However, ubiquitous warming across the region in the past 8 years, suggests the recent period of coastal cooling has ended. Significant warming trends are largely restricted to austral spring, summer and autumn seasons, with very few significant positive or negative trends in winter identified. Autumn warming is notably strong in the Andes, which, together with significant warming in spring, could help to explain the negative mass balance of snow and glaciers in the region. A strong Pacific maritime influence on regional temperature trends is inferred through correlation with the Interdecadal Pacific Oscillation (IPO) index and coastal sea surface temperature, but the strength of this influence rapidly diminishes inland, and the majority of valley, and all Andes, sites are independent of the IPO index. Instead, valley and Andes sites, and mid-troposphere temperature in the coastal radiosonde profile, show correlation with the autumn Antarctic Oscillation which, in its current positive phase, promotes subsidence and warming at the latitude of central Chile.

Temperature Trends in Montane Lakes

NASA Astrophysics Data System (ADS)

Melack, J. M.; Sadro, S.; Jellison, R.

2014-12-01

Long-term temperature trends in lakes integrate hydrological and meteorological factors. We examine temperature trends in a small montane lake with prolonged ice-cover and large seasonal snowfall and in a large saline lake. Emerald Lake, located in the Sierra Nevada (California), is representative of high-elevation lakes throughout the region. No significant trend in outflow temperature was apparent from 1991to 2012. Snowfall in the watershed accounted for 93% of the variability in average summer lake temperatures. Mono Lake (California) lies in a closed, montane basin and is hypersaline and monomictic or meromictic. Temperature profiles have been collected from 1982 to 2010. In the upper water column, the July-August-September water temperatures increased 0.8-1.0°C over the 29 years. This rate of warming is less than published estimates based on satellite-derived skin temperatures and will discussed in the context of general limnological interpretation of temperature trends.

Recent Short Term Global Aerosol Trends over Land and Ocean Dominated by Biomass Burning

NASA Technical Reports Server (NTRS)

Remer, Lorraine A.; Koren, Ilan; Kleidman, RIchard G.; Levy, Robert C.; Martins, J. Vanderlei; Kim, Kyu-Myong; Tanre, Didier; Mattoo, Shana; Yu, Hongbin

2007-01-01

NASA's MODIS instrument on board the Terra satellite is one of the premier tools to assess aerosol over land and ocean because of its high quality calibration and consistency. We analyze Terra-MODIS's seven year record of aerosol optical depth (AOD) observations to determine whether global aerosol has increased or decreased during this period. This record shows that AOD has decreased over land and increased over ocean. Only the ocean trend is statistically significant and corresponds to an increase in AOD of 0.009, or a 15% increase from background conditions. The strongest increasing trends occur over regions and seasons noted for strong biomass burning. This suggests that biomass burning aerosol dominates the increasing trend over oceans and mitigates the otherwise mostly negative trend over the continents.

Analysis of temperature trends in Northern Serbia

NASA Astrophysics Data System (ADS)

Tosic, Ivana; Gavrilov, Milivoj; Unkašević, Miroslava; Marković, Slobodan; Petrović, Predrag

2017-04-01

An analysis of air temperature trends in Northern Serbia for the annual and seasonal time series is performed for two periods: 1949-2013 and 1979-2013. Three data sets of surface air temperatures: monthly mean temperatures, monthly maximum temperatures, and monthly minimum temperatures are analyzed at 9 stations that have altitudes varying between 75 m and 102 m. Monthly mean temperatures are obtained as the average of the daily mean temperatures, while monthly maximum (minimum) temperatures are the maximum (minimum) values of daily temperatures in corresponding month. Positive trends were found in 29 out of 30 time series, and the negative trend was found only in winter during the period 1979-2013. Applying the Mann-Kendall test, significant positive trends were found in 15 series; 7 in the period 1949-2013 and 8 in the period 1979-2013; and no significant trend was found in 15 series. Significant positive trends are dominated during the year, spring, and summer, where it was found in 14 out of 18 cases. Significant positive trends were found 7, 5, and 3 times in mean, maximum and minimum temperatures, respectively. It was found that the positive temperature trends are dominant in Northern Serbia.

Satellite-based global-ocean mass balance estimates of interannual variability and emerging trends in continental freshwater discharge

PubMed Central

Syed, Tajdarul H.; Famiglietti, James S.; Chambers, Don P.; Willis, Josh K.; Hilburn, Kyle

2010-01-01

Freshwater discharge from the continents is a key component of Earth’s water cycle that sustains human life and ecosystem health. Surprisingly, owing to a number of socioeconomic and political obstacles, a comprehensive global river discharge observing system does not yet exist. Here we use 13 years (1994–2006) of satellite precipitation, evaporation, and sea level data in an ocean mass balance to estimate freshwater discharge into the global ocean. Results indicate that global freshwater discharge averaged 36,055 km3/y for the study period while exhibiting significant interannual variability driven primarily by El Niño Southern Oscillation cycles. The method described here can ultimately be used to estimate long-term global discharge trends as the records of sea level rise and ocean temperature lengthen. For the relatively short 13-year period studied here, global discharge increased by 540 km3/y2, which was largely attributed to an increase of global-ocean evaporation (768 km3/y2). Sustained growth of these flux rates into long-term trends would provide evidence for increasing intensity of the hydrologic cycle. PMID:20921364

A Novel Method making direct use of AIRS and IASI Calibrated Radiances for Measuring Trends in Surface Temperatures

NASA Astrophysics Data System (ADS)

Aumann, H. H.; Ruzmaikin, A.

2014-12-01

Making unbiased measurements of trends in the surface temperatures, particularly on a gobal scale, is challenging: While the non-frozen oceans temperature measurements are plentiful and accurate, land and polar areas are much less accurately or fairly sampled. Surface temperature deduced from infrared radiometers on polar orbiting satellites (e.g. the Atmospheric Infrared Sounder (AIRS) at 1:30PM, the Interferometer Atmosphere Sounding Interferometer (IASI) at 9:30 AM and the MODerate resolution Imaging Spectro-radiometer (MODIS) at 1:30PM), can produce what appear to be well sampled data, but dealing with clouds either by cloud filtering (MODIS, IASI) or cloud-clearing (AIRS) can create sampling bias. We use a novel method: Random Nadir Sampling (RNS) combined with Probability Density Function (PDF) analysis. We analyze the trend in the PDF of st1231, the water vapor absorption corrected brightness temperatures measured in the 1231 cm-1 atmospheric window channel. The advantage of this method is that trends can be directly traced to the known, less than 3 mK/yr trend for AIRS, in st1231. For this study we created PDFs from 22,000 daily RNS from the AIRS and IASI data. We characterized the PDFs by its daily 90%tile value, st1231p90, and analysed the statistical properties of the this time series between 2002 and 2014. The method was validated using the daily NOAA SST (RTGSST) from the non-frozen oceans: The mean, seasonal variability and anomaly trend of st1231p90 agree with the corrsponding values from the RTGSST and the anomaly correlation is larger than 0.9. Preliminary results (August 2014) confirm the global hiatus in the increase of the globally averaged surface temperatures between 2002 and 2014, with a change of less than 10 mK/yr. This uncertainty is dominated by the large interannual variability related to El Niño events. Further insite is gained by analyzing land/ocean, day/night, artic and antarctic trends. We observe a massive warming trend in the

Role of the North Atlantic Oscillation in decadal temperature trends

NASA Astrophysics Data System (ADS)

Iles, Carley; Hegerl, Gabriele

2017-11-01

Global temperatures have undergone periods of enhanced warming and pauses over the last century, with greater variations at local scales due to internal variability of the climate system. Here we investigate the role of the North Atlantic Oscillation (NAO) in decadal temperature trends in the Northern Hemisphere for periods with large decadal NAO trends. Using a regression based technique we find a best estimate that trends in the NAO more than halved (reduced by 57%, 5%-95%: 47%-63%) the winter warming over the Northern Hemisphere extratropics (NH; 30N-90N) from 1920-1971 and account for 45% (±14%) of the warming there from 1963-1995, with larger impacts on regional scales. Over the period leading into the so-called warming hiatus, 1989-2013, the NAO reduced NH winter warming to around one quarter (24%; 19%-31%) of what it would have been, and caused large negative regional trends, for example, in Northern Eurasia. Warming is more spatially uniform across the Northern Hemisphere after removing the NAO influence in winter, and agreement with multi-model mean simulated trends improves. The impact of the summer NAO is much weaker, but still discernible over Europe, North America and Greenland, with the downward trend in the summer NAO from 1988-2012 reducing warming by about a third in Northern Europe and a half in North America. A composite analysis using CMIP5 control runs suggests that the ocean response to prolonged NAO trends may increase the influence of decadal NAO trends compared to estimates based on interannual regressions, particularly in the Arctic. Results imply that the long-term NAO trends over the 20th century alternately masked or enhanced anthropogenic warming, and will continue to temporarily offset or enhance its effects in the future.

Trends and variability of the atmosphere–ocean turbulent heat flux in the extratropical Southern Hemisphere

PubMed Central

Herman, Agnieszka

2015-01-01

Ocean–atmosphere interactions are complex and extend over a wide range of temporal and spatial scales. Among the key components of these interactions is the ocean–atmosphere (latent and sensible) turbulent heat flux (THF). Here, based on daily optimally-interpolated data from the extratropical Southern Hemisphere (south of 30°S) from a period 1985–2013, we analyze short-term variability and trends in THF and variables influencing it. It is shown that, in spite of climate-change-related positive trends in surface wind speeds over large parts of the Southern Ocean, the range of the THF variability has been decreasing due to decreasing air–water temperature and humidity differences. Occurrence frequency of very large heat flux events decreased accordingly. Remarkably, spectral analysis of the THF data reveals, in certain regions, robust periodicity at frequencies 0.03–0.04 day−1, corresponding exactly to frequencies of the baroclinic annular mode (BAM). Finally, it is shown that the THF is correlated with the position of the major fronts in sections of the Antarctic Circumpolar Current where the fronts are not constrained by the bottom topography and can adjust their position to the atmospheric and oceanic forcing, suggesting differential response of various sections of the Southern Ocean to the changing atmospheric forcing. PMID:26449323

Temperature evolution and the oxygen isotope composition of Phanerozoic oceans from carbonate clumped isotope thermometry

NASA Astrophysics Data System (ADS)

Henkes, Gregory A.; Passey, Benjamin H.; Grossman, Ethan L.; Shenton, Brock J.; Yancey, Thomas E.; Pérez-Huerta, Alberto

2018-05-01

Surface temperature is among the most important parameters describing planetary climate and habitability, and yet there remains considerable debate about the temperature evolution of the Earth's oceans during the Phanerozoic Eon (541 million years ago to present), the time during which complex metazoan life radiated on Earth. Here we critically assess the emerging record of Phanerozoic ocean temperatures based on carbonate clumped isotope thermometry of fossil brachiopod and mollusk shells, and we present new data that fill important gaps in the Late Paleozoic record. We evaluate and reject the hypothesis that solid-state reordering of 13C-18O bonds has destroyed the primary clumped isotope temperature signal of most fossils during sedimentary burial at elevated temperatures. The resulting Phanerozoic record, which shows a general coupling between tropical seawater temperatures and atmospheric carbon dioxide (CO2) levels since the Paleozoic, indicates that tropical temperatures during the icehouse climate of the Carboniferous period were broadly similar to present (∼25-30 °C), and suggests that benthic metazoans were able to thrive at temperatures of 35-40 °C during intervals of the early and possibly the latest Paleozoic when CO2 levels were likely 5-10× higher than present-day values. Equally important, there is no resolvable trend in seawater oxygen isotope ratios (δ18 O) over the past ∼500 million years, indicating that the average temperature of oxygen exchange between seawater and the oceanic crust has been high (∼270 °C) since at least the early Paleozoic, which points to mid-ocean ridges as the dominant locus of water-rock interaction over the past half-billion years.

Ocean heat content variability in an ensemble of twentieth century ocean reanalyses

NASA Astrophysics Data System (ADS)

de Boisséson, Eric; Balmaseda, Magdalena Alonso; Mayer, Michael

2017-08-01

This paper presents a ten-member ensemble of twentieth century Ocean ReAnalyses called ORA-20C. ORA-20C assimilates temperature and salinity profiles and is forced by the ECMWF twentieth century atmospheric reanalysis (ERA-20C) over the 1900-2010 period. This study attempts to identify robust signals of ocean heat content change in ORA-20C and detect contamination by model errors, initial condition uncertainty, surface fluxes and observing system changes. It is shown that ORA-20C trends and variability in the first part of the century result from the surface fluxes and model drift towards a warmer mean state and weak meridional overturning circulation. The impact of the observing system in correcting the mean state causes the deceleration of the warming trend and alters the long-term climate signal. The ensemble spread reflects the long-lasting memory of the initial conditions and the convergence of the system to a solution compatible with surface fluxes, the ocean model and observational constraints. Observations constrain the ocean heat uptake trend in the last decades of the twentieth century, which is similar to trend estimations from the post-satellite era. An ocean heat budget analysis attributes ORA-20C heat content changes to surface fluxes in the first part of the century. The heat flux variability reflects spurious signals stemming from ERA-20C surface fields, which in return result from changes in the atmospheric observing system. The influence of the temperature assimilation increments on the heat budget is growing with time. Increments control the most recent ocean heat uptake signals, highlighting imbalances in forced reanalysis systems in the ocean as well as in the atmosphere.

Temperature Trends in the Tropical Upper Troposphere and Lower Stratosphere: Connections with Sea Surface Temperatures and Implications for Water Vapor and Ozone

NASA Technical Reports Server (NTRS)

Garfinkel, C. I.; Waugh, D. W.; Oman, L. D.; Wang, L.; Hurwitz, M. M.

2013-01-01

Satellite observations and chemistry-climate model experiments are used to understand the zonal structure of tropical lower stratospheric temperature, water vapor, and ozone trends. The warming in the tropical upper troposphere over the past 30 years is strongest near the Indo-Pacific warm pool, while the warming trend in the western and central Pacific is much weaker. In the lower stratosphere, these trends are reversed: the historical cooling trend is strongest over the Indo-Pacific warm pool and is weakest in the western and central Pacific. These zonal variations are stronger than the zonal-mean response in boreal winter. Targeted experiments with a chemistry-climate model are used to demonstrate that sea surface temperature (hereafter SST) trends are driving the zonal asymmetry in upper tropospheric and lower stratospheric tropical temperature trends. Warming SSTs in the Indian Ocean and in the warm pool region have led to enhanced moist heating in the upper troposphere, and in turn to a Gill-like response that extends into the lower stratosphere. The anomalous circulation has led to zonal structure in the ozone and water vapor trends near the tropopause, and subsequently to less water vapor entering the stratosphere. The radiative impact of these changes in trace gases is smaller than the direct impact of the moist heating. Projected future SSTs appear to drive a temperature and water vapor response whose zonal structure is similar to the historical response. In the lower stratosphere, the changes in water vapor and temperature due to projected future SSTs are of similar strength to, though slightly weaker than, that due directly to projected future CO2, ozone, and methane.

Interhemispheric SST gradient trends in the Indian Ocean prior to and during the recent global warming hiatus

NASA Astrophysics Data System (ADS)

Dong, L.; McPhaden, M. J.

2016-12-01

Sea surface temperatures (SSTs) have been rising for decades in the Indian Ocean in response to greenhouse gas forcing. However, in this study we show that during the recent hiatus in global warming, a striking interhemispheric gradient in Indian Ocean SST trends developed around 2000, with relatively weak or little warming to the north of 10°S and accelerated warming to the south of 10oS. We present evidence from a wide variety of data sources that this interhemispheric gradient in SST trends is forced primarily by an increase of Indonesian Throughflow (ITF) transport from the Pacific into the Indian Ocean induced by stronger Pacific trade winds. This increased transport led to a depression of the thermocline that facilitated SST warming presumably through a reduction in the vertical turbulent transport of heat in the southern Indian Ocean. Surface wind changes in the Indian Ocean linked to the enhanced Walker circulation also may have contributed to thermocline depth variations and associated SST changes, with downwelling favorable wind stress curls between 10oS and 20oS and upwelling favorable wind stress curls between the equator and 10oS. In addition, the anomalous southwesterly wind stresses off the coast of Somalia favored intensified coastal upwelling and off-shore advection of upwelled water, which would have led to reduced warming of the northern Indian Ocean. Though highly uncertain, lateral heat advection associated with the ITF and surface heat fluxes may also have played a role in forming the interhemispheric SST gradient change.

Increasing trend in the average temperature in Finland, 1847-2012

NASA Astrophysics Data System (ADS)

Mikkonen, Santtu; Laine, Marko; Mäkelä, Hanna M.; Gregow, Hilppa; Tuomenvirta, Heikki; Lahtinen, Matti; Laaksonen, Ari

2014-05-01

The global average temperature has increased by about 0.8 ° C since the mid-19th century. It has been shown that this increase is statistically significant and that it can, for the most part, be attributed to human-induced climate change (IPCC 2007). A temperature increase is obvious also in regional and local temperatures in many parts of the world. However, compared with the global average temperature, the regional and local temperatures exhibit higher levels of noise, which has largely been removed from the global temperature due to the higher level of averaging. Because Finland is located in northern latitudes, it is subject to the polar amplification of climate change-induced warming, which is due to the enhanced melting of snow and ice and other feedback mechanisms. Therefore, warming in Finland is expected to be approximately 50% higher than the global average. Conversely, the location of Finland between the Atlantic Ocean and continental Eurasia causes the weather to be very variable, and thus the temperature signal is rather noisy. The change in mean temperature in Finland was investigated with Dynamic Linear Models (DLM) in order to define the sign and the magnitude of the trend in the temperature time series within the last 165 years. The data consisted of gridded monthly mean temperatures. The grid has a 10 km spatial resolution, and it was created by interpolating a homogenized temperature series measured at Finnish weather stations. Seasonal variation in temperature and the autocorrelation structure of the time series were taken account in the DLM models. We found that the Finnish temperature time series exhibits a statistically significant increasing trend, which is consistent with human-induced global warming. The mean temperature has risen clearly over 2° C in the years 1847-2012, which amounts to 0.16 ° C/decade. The warming rate before 1940's was close to the linear trend for the whole period, whereas the temperature change in the mid-20th

Calibration Uncertainty in Ocean Color Satellite Sensors and Trends in Long-term Environmental Records

NASA Technical Reports Server (NTRS)

Turpie, Kevin R.; Eplee, Robert E., Jr.; Franz, Bryan A.; Del Castillo, Carlos

2014-01-01

Launched in late 2011, the Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership (NPP) spacecraft is being evaluated by NASA to determine whether this sensor can continue the ocean color data record established through the Sea-Viewing Wide Field-of-view Sensor (SeaWiFS) and the MODerate resolution Imaging Spectroradiometer (MODIS). To this end, Goddard Space Flight Center generated evaluation ocean color data products using calibration techniques and algorithms established by NASA during the SeaWiFS and MODIS missions. The calibration trending was subjected to some initial sensitivity and uncertainty analyses. Here we present an introductory assessment of how the NASA-produced time series of ocean color is influenced by uncertainty in trending instrument response over time. The results help quantify the uncertainty in measuring regional and global biospheric trends in the ocean using satellite remote sensing, which better define the roles of such records in climate research.

Global Trends in Chlorophyll Concentration Observed with the Satellite Ocean Colour Data Record

NASA Astrophysics Data System (ADS)

Melin, F.; Vantrepotte, V.; Chuprin, A.; Grant, M.; Jackson, T.; Sathyendranath, S.

2016-08-01

To detect climate change signals in the data records derived from remote sensing of ocean colour, combining data from multiple missions is required, which implies that the existence of inter-mission differences be adequately addressed prior to undertaking trend studies. Trend distributions associated with merged products are compared with those obtained from single-mission data sets in order to evaluate their suitability for climate studies. Merged products originally developed for operational applications such as near-real time distribution (GlobColour) do not appear to be proper climate data records, showing large parts of the ocean with trends significantly different from trends obtained with SeaWiFS, MODIS or MERIS. On the other hand, results obtained from the Climate Change Initiative (CCI) data are encouraging, showing a good consistency with single-mission products.

Pacific Ocean buoy temperature date

EPA Pesticide Factsheets

Pacific Ocean buoy temperature dataThis dataset is associated with the following publication:Carbone, F., M. Landis, C.N. Gencarelli, A. Naccarato, F. Sprovieri, F. De Simone, I.M. Hedgecock, and N. Pirrone. Sea surface temperature variation linked to elemental mercury concentrations measured on Mauna Loa. GEOPHYSICAL RESEARCH LETTERS. American Geophysical Union, Washington, DC, USA, online, (2016).

Enhanced Pacific Ocean Sea Surface Temperature and Its Relation to Typhoon Haiyan

NASA Technical Reports Server (NTRS)

Comiso, Josefino C.; Perez, Gay Jane P.; Stock, Larry V.

2015-01-01

Typhoon Haiyan, which devastated the Visayan Islands in the Philippines on November 8, 2013 was recorded as the strongest typhoon ever-observed using satellite data. Typhoons in the region usually originate from the mid-Pacific region that includes the Warm Pool, which is regarded as the warmest ocean surface region globally. Two study areas were considered: one in the Warm Pool Region and the other in the West Pacific Region near the Philippines. Among the most important factors that affect the strength of a typhoon are sea surface temperature (SST) and water vapor. It is remarkable that in November 2013 the average SST in the Warm Pool Region was the highest observed during the 1981 to 2014 period while that of the West Pacific Region was among the highest as well. Moreover, the increasing trend in SST was around 0.20C per decade in the warm pool region and even higher at 0.23C per decade in the West Pacific region. The yearly minimum SST has also been increasing suggesting that the temperature of the ocean mixed layer is also increasing. Further analysis indicated that water vapor, clouds, winds and sea level pressure for the same period did not reveal strong signals associated with the 2013 event. The SST is shown to be well-correlated with wind strength of historically strong typhoons in the country and the observed trends in SST suggest that extremely destructive typhoons like Haiyan are likely to occur in the future.

Comparison of Mean Climate Trends in the Northern Hemisphere Between N.C.E.P. and Two Atmosphere-Ocean Model Forced Runs

NASA Technical Reports Server (NTRS)

Lucarini, Valerio; Russell, Gary L.; Hansen, James E. (Technical Monitor)

2002-01-01

Results are presented for two greenhouse gas experiments of the Goddard Institute for Space Studies Atmosphere-Ocean Model (AOM). The computed trends of surface pressure, surface temperature, 850, 500 and 200 mb geopotential heights and related temperatures of the model for the time frame 1960-2000 are compared to those obtained from the National Centers for Environmental Prediction observations. A spatial correlation analysis and mean value comparison are performed, showing good agreement. A brief general discussion about the statistics of trend detection is presented. The domain of interest is the Northern Hemisphere (NH) because of the higher reliability of both the model results and the observations. The accuracy that this AOM has in describing the observed regional and NH climate trends makes it reliable in forecasting future climate changes.

Tropical Indian Ocean warming contributions to China winter climate trends since 1960

NASA Astrophysics Data System (ADS)

Wu, Qigang; Yao, Yonghong; Liu, Shizuo; Cao, DanDan; Cheng, Luyao; Hu, Haibo; Sun, Leng; Yao, Ying; Yang, Zhiqi; Gao, Xuxu; Schroeder, Steven R.

2018-01-01

This study investigates observed and modeled contributions of global sea surface temperature (SST) to China winter climate trends in 1960-2014, including increased precipitation, warming through about 1997, and cooling since then. Observations and Atmospheric Model Intercomparison Project (AMIP) simulations with prescribed historical SST and sea ice show that tropical Indian Ocean (TIO) warming and increasing rainfall causes diabatic heating that generates a tropospheric wave train with anticyclonic 500-hPa height anomaly centers in the TIO or equatorial western Pacific (TIWP) and northeastern Eurasia (EA) and a cyclonic anomaly over China, referred to as the TIWP-EA wave train. The cyclonic anomaly causes Indochina moisture convergence and southwesterly moist flow that enhances South China precipitation, while the northern anticyclone enhances cold surges, sometimes causing severe ice storms. AMIP simulations show a 1960-1997 China cooling trend by simulating increasing instead of decreasing Arctic 500-hPa heights that move the northern anticyclone into Siberia, but enlarge the cyclonic anomaly so it still simulates realistic China precipitation trend patterns. A separate idealized TIO SST warming simulation simulates the TIWP-EA feature more realistically with correct precipitation patterns and supports the TIWP-EA teleconnection as the primary mechanism for long-term increasing precipitation in South China since 1960. Coupled Model Intercomparison Project (CMIP) experiments simulate a reduced TIO SST warming trend and weak precipitation trends, so the TIWP-EA feature is absent and strong drying is simulated in South China for 1960-1997. These simulations highlight the need for accurately modeled SST to correctly attribute regional climate trends.

Regional acidification trends in Florida shellfish estuaries: A 20+ year look at pH, oxygen, temperature, and salinity

USGS Publications Warehouse

Robbins, Lisa L.; Lisle, John T.

2018-01-01

Increasing global CO2 and local land use changes coupled with increased nutrient pollution are threatening estuaries worldwide. Local changes of estuarine chemistry have been documented, but regional associations and trends comparing multiple estuaries latitudinally have not been evaluated. Rapid climate change has impacted the annual and decadal chemical trends in estuaries, with local ecosystem processes enhancing or mitigating the responses. Here, we compare pH, dissolved oxygen, temperature, and salinity data from 10 Florida shellfish estuaries and hundreds of shellfish bed stations. Over 80,000 measurements, spanning from 1980 to 2008, taken on Atlantic Ocean and West Florida coast showed significant regional trends of consistent pH decreases in 8 out of the 10 estuaries, with an average rate of decrease on the Gulf of Mexico side estuaries of Florida of 7.3 × 10−4 pH units year−1, and average decrease on the Atlantic Coast estuaries of 5.0 × 10−4 pH units year−1. The rates are approximately 2–3.4 times slower than observed in pH decreases associated with ocean acidification in the Atlantic and Pacific. Other significant trends observed include decreasing dissolved oxygen in 9 out of the 10 estuaries, increasing salinity in 6 out of the 10, and temperature increases in 3 out of the 10 estuaries. The data provide a synoptic regional view of Florida estuary trends which reflect the complexity of changing climate and coastal ocean acidification superimposed on local conditions. These data provide context for understanding, and interpreting the past and predicting future of regional water quality health of shellfish and other organisms of commercial and ecological significance along Florida’s coasts.

Stratospheric temperature trends: History of our evolving understanding

NASA Astrophysics Data System (ADS)

Seidel, D. J.; Gillett, N. P.; Lanzante, J.; Shine, K. P.; Thorne, P.

2010-12-01

Changes in greenhouse gas and stratospheric ozone concentrations are known to force long-term trends in stratospheric temperature. Therefore, national and international assessments of climate change and stratospheric ozone depletion over the past several decades have included discussion of observed and projected stratospheric temperature trends. Similarly, tropospheric temperature trends have figured prominently in the climate change literature; they have been the subject of considerable controversy. Although many of the same modeling and observational tools have been applied, and there are many common scientific issues in both regions of the atmosphere, stratospheric temperatures have not captured the imagination of the public, the popular press and public policy community. We present an historical review of our evolving understanding of stratospheric temperature trends, including both observational and modeling perspectives, from the 1970’s to present. Comparisons and contrasts will be drawn between the stratospheric and tropospheric temperature trend literature, including observing systems, dataset development for trend estimates, modeling approaches, and associated uncertainties. Recent developments will be highlighted.

Current and Future Decadal Trends in the Oceanic Carbon Uptake Are Dominated by Internal Variability

NASA Astrophysics Data System (ADS)

Li, Hongmei; Ilyina, Tatiana

2018-01-01

We investigate the internal decadal variability of the ocean carbon uptake using 100 ensemble simulations based on the Max Planck Institute Earth system model (MPI-ESM). We find that on decadal time scales, internal variability (ensemble spread) is as large as the forced temporal variability (ensemble mean), and the largest internal variability is found in major carbon sink regions, that is, the 50-65°S band of the Southern Ocean, the North Pacific, and the North Atlantic. The MPI-ESM ensemble produces both positive and negative 10 year trends in the ocean carbon uptake in agreement with observational estimates. Negative decadal trends are projected to occur in the future under RCP4.5 scenario. Due to the large internal variability, the Southern Ocean and the North Pacific require the most ensemble members (more than 53 and 46, respectively) to reproduce the forced decadal trends. This number increases up to 79 in future decades as CO2 emission trajectory changes.

Trends in Arctic Ocean bottom pressure, sea surface height and freshwater content using GRACE and the ice-ocean model PIOMAS from 2008-2012

NASA Astrophysics Data System (ADS)

Peralta-Ferriz, Cecilia; Morison, James; Zhang, Jinlun; Bonin, Jennifer

2014-05-01

The variability of ocean bottom pressure (OBP) in the Arctic is dominated by the variations in sea surface height (SSH) from daily to monthly timescales. Conversely, OBP variability is dominated by the changes in the steric pressure (StP) at inter-annual timescales, particularly off the continental shelves. The combination of GRACE-derived ocean bottom pressure and ICESat altimetry-derived sea surface height variations in the Arctic Ocean have provided new means of identifying inter-annual trends in StP (StP = OBP-SSH) and associated freshwater content (FWC) of the Arctic region (Morison et al., 2012). Morison et al. (2012) showed that from 2004 to 2008, the FWC increased in the Beaufort Gyre and decreased in the Siberian and Central Arctic, resulting in a relatively small net basin-averaged FWC change. In this work, we investigate the inter-annual trends from 2008 to 2012 in OBP from GRACE, SSH from the state-of-the-art pan-Arctic ocean model PIOMAS -validated with tide and pressure gauges in the Arctic-, and compute the trends in StP and FWC from 2008-2012. We compare these results with the previous trends from 2005-2008 described in Morison et al. (2012). Our initial findings suggest increased salinity in the entire Arctic basin (relative to the climatological seasonal variation) from 2008-2012, compared to the preceding four years (2005-2008). We also find that the trends in OBP, SSH and StP from 2008-2012 present a different behavior during the spring-summer and fall-winter, unlike 2005-2008, in which the trends were generally consistent through all months of the year. It seems since 2009, when the Beaufort Gyre relaxed and the export of freshwater from the Canada Basin into the Canadian Archipelago and Fram Strait, via the Lincoln Sea, was anomalously large (de Steur et al., 2013), the Arctic Ocean has entered a new circulation regime. The causes of such changes in the inter-annual trends of OBP, SSH and StP -hence FWC-, associated with the changes in the

Understanding Southern Ocean SST Trends in Historical Simulations and Observations

NASA Astrophysics Data System (ADS)

Kostov, Yavor; Ferreira, David; Marshall, John; Armour, Kyle

2017-04-01

Historical simulations with CMIP5 global climate models do not reproduce the observed 1979-2014 Southern Ocean (SO) cooling, and most ensemble members predict gradual warming around Antarctica. In order to understand this discrepancy and the mechanisms behind the SO cooling, we analyze output from 19 CMIP5 models. For each ensemble member we estimate the characteristic responses of SO SST to step changes in greenhouse gas (GHG) forcing and in the seasonal indices of the Southern Annular Mode (SAM). Using these step-response functions and linear convolution theory, we reconstruct the original CMIP5 simulations of 1979-2014 SO SST trends. We recover the CMIP5 ensemble mean trend, capture the intermodel spread, and reproduce very well the behavior of individual models. We thus suggest that GHG forcing and the SAM are major drivers of the simulated 1979-2014 SO SST trends. In consistence with the seasonal signature of the Antarctic ozone hole, our results imply that the summer (DJF) and fall (MAM) SAM exert a particularly important effect on the SO SST. In some CMIP5 models the SO SST response to SAM partially counteracts the warming due to GHG forcing, while in other ensemble members the SAM-induced SO SST trends complement the warming effect of GHG forcing. The compensation between GHG and SAM-induced SO SST anomalies is model-dependent and is determined by multiple factors. Firstly, CMIP5 models have different characteristic SST step response functions to SAM. Kostov et al. (2016) relate these differences to biases in the models' climatological SO temperature gradients. Secondly, many CMIP5 historical simulations underestimate the observed positive trends in the DJF and MAM seasonal SAM indices. We show that this affects the models' ability to reproduce the observed SO cooling. Last but not least, CMIP5 models differ in their SO SST step response functions to GHG forcing. Understanding the diverse behavior of CMIP5 models helps shed light on the physical processes

Three modes of interdecadal trends in sea surface temperature and sea surface height

NASA Astrophysics Data System (ADS)

Gnanadesikan, A.; Pradal, M.

2013-12-01

It might be thought that sea surface height and sea surface temperature would be tightly related. We show that this is not necessarily the case on a global scale. We analysed this relationship in a suite of coupled climate models run under 1860 forcing conditions. The models are low-resolution variants of the GFDL Earth System Model, reported in Galbraith et al. (J. Clim. 2011). 1. Correlated changes in global sea surface height and global sea surface temperature. This mode corresponds to opening and closing of convective chimneys in the Southern Ocean. As the Southern Ocean destratifies, sea ice formation is suppressed during the winter and more heat is taken up during the summer. This mode of variability is highly correlated with changes in the top of the atmosphere radiative budget and weakly correlated with changes in the deep ocean circulation. 2. Uncorrelated changes in global sea surface height and global sea surface temperature. This mode of variability is associated with interdecadal variabliity in tropical winds. Changes in the advective flux of heat to the surface ocean play a critical role in driving these changes, which also result in significant local changes in sea level. Changes sea ice over the Southern Ocean still result in changes in solar absorption, but these are now largely cancelled by changes in outgoing longwave radiation. 3. Anticorrelated changes in global sea surface height and global sea surface temperatures. By varying the lateral diffusion coefficient in the ocean model, we are able to enhance and suppress convection in the Southern and Northern Pacific Oceans. Increasing the lateral diffusion coefficients shifts the balance sources of deep water away from the warm salty deep water of the North Atlantic and towards cold fresh deep water from the other two regions. As a result, even though the planet as a whole warms, the deep ocean cools and sea level falls, with changes of order 30 cm over 500 years. The increase in solar absorption

Decadal trends in global pelagic ocean chlorophyll: A new assessment integrating multiple satellites, in situ data, and models.

PubMed

Gregg, Watson W; Rousseaux, Cécile S

2014-09-01

Quantifying change in ocean biology using satellites is a major scientific objective. We document trends globally for the period 1998-2012 by integrating three diverse methodologies: ocean color data from multiple satellites, bias correction methods based on in situ data, and data assimilation to provide a consistent and complete global representation free of sampling biases. The results indicated no significant trend in global pelagic ocean chlorophyll over the 15 year data record. These results were consistent with previous findings that were based on the first 6 years and first 10 years of the SeaWiFS mission. However, all of the Northern Hemisphere basins (north of 10° latitude), as well as the Equatorial Indian basin, exhibited significant declines in chlorophyll. Trend maps showed the local trends and their change in percent per year. These trend maps were compared with several other previous efforts using only a single sensor (SeaWiFS) and more limited time series, showing remarkable consistency. These results suggested the present effort provides a path forward to quantifying global ocean trends using multiple satellite missions, which is essential if we are to understand the state, variability, and possible changes in the global oceans over longer time scales.

Pliocene three-dimensional global ocean temperature reconstruction

USGS Publications Warehouse

Dowsett, H.J.; Robinson, M.M.; Foley, K.M.

2009-01-01

The thermal structure of the mid-Piacenzian ocean is obtained by combining the Pliocene Research, Interpretation and Synoptic Mapping Project (PRISM3) multiproxy sea-surface temperature (SST) reconstruction with bottom water temperature estimates from 27 locations produced using Mg/Ca paleothermometry based upon the ostracod genus Krithe. Deep water temperature estimates are skewed toward the Atlantic Basin (63% of the locations) and represent depths from 1000m to 4500 m. This reconstruction, meant to serve as a validation data set as well as an initialization for coupled numerical climate models, assumes a Pliocene water mass framework similar to that which exists today, with several important modifications. The area of formation of present day North Atlantic Deep Water (NADW) was expanded and extended further north toward the Arctic Ocean during the mid-Piacenzian relative to today. This, combined with a deeper Greenland-Scotland Ridge, allowed a greater volume of warmer NADW to enter the Atlantic Ocean. In the Southern Ocean, the Polar Front Zone was expanded relative to present day, but shifted closer to the Antarctic continent. This, combined with at least seasonal reduction in sea ice extent, resulted in decreased Antarctic Bottom Water (AABW) production (relative to present day) as well as possible changes in the depth of intermediate waters. The reconstructed mid-Piacenzian three-dimensional ocean was warmer overall than today, and the hypothesized aerial extent of water masses appears to fit the limited stable isotopic data available for this time period. ?? Author(s) 2009.

Comparison of mean climate trends in the Northern Hemisphere between National Centers for Environmental Prediction and two atmosphere-ocean model forced runs

NASA Astrophysics Data System (ADS)

Lucarini, Valerio; Russell, Gary L.

2002-08-01

Results are presented for two greenhouse gas experiments of the Goddard Institute for Space Studies atmosphere-ocean model (AOM). The computed trends of surface pressure; surface temperature; 850, 500, and 200 mbar geopotential heights; and related temperatures of the model for the time frame 1960-2000 are compared with those obtained from the National Centers for Enviromental Prediction (NCEP) observations. The domain of interest is the Northern Hemisphere because of the higher reliability of both the model results and the observations. A spatial correlation analysis and a mean value comparison are performed, showing good agreement in terms of statistical significance for most of the variables considered in the winter and annual means. However, the 850 mbar temperature trends do not show significant positive correlation, and the surface pressure and 850 mbar geopotential height mean trends confidence intervals do not overlap. A brief general discussion about the statistics of trend detection is presented. The accuracy that this AOM has in describing the regional and NH mean climate trends inferred from NCEP through the atmosphere suggests that it may be reliable in forecasting future climate changes.

Trend and Variability of China Precipitation in Spring and Summer: Linkage to Sea Surface Temperatures

NASA Technical Reports Server (NTRS)

Yang, Fanglin; Lau, K.-M.

2004-01-01

Observational records in the past 50 years show an upward trend of boreal-summer precipitation over central eastern China and a downward trend over northern China. During boreal spring, the trend is upward over southeastern China and downward over central eastern China. This study explores the forcing mechanism of these trends in association with the global sea-surface temperature (SST) variations on the interannual and inter-decadal timescales. Results based on Singular Value Decomposition analyses (SVD) show that the interannual variability of China precipitation in boreal spring and summer can be well defined by two centers of actions for each season, which are co-varying with two interannual modes of SSTs. The first SVD modes of precipitation in spring and summer, which are centered in southeastern China and northern China, respectively, are linked to an ENSO-like mode of SSTs. The second SVD modes of precipitation in both seasons are confined to central eastern China, and are primarily linked to SST variations over the warm pool and Indian Ocean. Features of the anomalous 850-hPa winds and 700-Wa geopotential height corresponding to these modes support a physical mechanism that explains the causal links between the modal variations of precipitation and SSTs. On the decadal and longer timescale, similar causal links are found between the same modes of precipitation and SSTs, except for the case of springtime precipitation over central eastern China. For this case, while the interannual mode of precipitation is positively correlated with the interannual variations of SSTs over the warm pool and Indian Ocean; the inter-decadal mode is negatively correlated with a different SST mode, the North Pacific mode. The later is responsible for the observed downward trend of springtime precipitation over central eastern China. For all other cases, both the interannual and inter-decadal variations of precipitation can be explained by the same mode of SSTs. The upward trend

Identifying meaningful trends in Atlantic water temperature from sparse in situ hydrographic observations from the periphery of the Greenland Ice Sheet

NASA Astrophysics Data System (ADS)

Fenty, I. G.; Willis, J. K.; Rignot, E. J.

2016-12-01

Motivated by the need to understand the connection between the warming North Atlantic Ocean and increasing ice mass loss from the Greenland Ice Sheet, in 2015 we initiated "Oceans Melting Greenland" (OMG), a 5-year NASA sub-orbital mission. One component of OMG is a once-yearly sampling of full-depth vertical profiles of ocean temperature and salinity around Greenland's continental shelf at 250 locations. These measurements have the potential to provide an unprecedented view of ocean properties around Greenland, especially the warm, salty subsurface Atlantic Waters that have been implicated in tidewater glacier retreat, acceleration, and thinning. However, OMG'S ocean measurements are essentially large-scale synoptic snapshots of an ocean state whose characteristic scales of temporal and spatial variability around Greenland are largely unknown. In this talk we discuss how high-resolution numerical ocean modelling is being employed to quantitatively estimate the region's natural hydrographic variability for the dual purposes of (1) informing our pan-Greenland ocean sampling strategy and (2) informing our interpretation of temperature trends in the data. OMG hydrographic shelf data collected in ship-based CTDs (2015, 2016) and Airborne eXpendable CTDs (2016) will be examined in the context of this estimated ocean variability.

Spatial distribution of unidirectional trends in temperature and temperature extremes in Pakistan

NASA Astrophysics Data System (ADS)

Khan, Najeebullah; Shahid, Shamsuddin; Ismail, Tarmizi bin; Wang, Xiao-Jun

2018-06-01

Pakistan is one of the most vulnerable countries of the world to temperature extremes due to its predominant arid climate and geographic location in the fast temperature rising zone. Spatial distribution of the trends in annual and seasonal temperatures and temperature extremes over Pakistan has been assessed in this study. The gauge-based gridded daily temperature data of Berkeley Earth Surface Temperature (BEST) having a spatial resolution of 1° × 1° was used for the assessment of trends over the period 1960-2013 using modified Mann-Kendall test (MMK), which can discriminate the multi-decadal oscillatory variations from secular trends. The results show an increase in the annual average of daily maximum and minimum temperatures in 92 and 99% area of Pakistan respectively at 95% level of confidence. The annual temperature is increasing faster in southern high-temperature region compared to other parts of the country. The minimum temperature is rising faster (0.17-0.37 °C/decade) compared to maximum temperature (0.17-0.29 °C/decade) and therefore declination of diurnal temperature range (DTR) (- 0.15 to - 0.08 °C/decade) in some regions. The annual numbers of both hot and cold days are increasing in whole Pakistan except in the northern sub-Himalayan region. Heat waves are on the rise, especially in the hot Sindh plains and the Southern coastal region, while the cold waves are becoming lesser in the northern cold region. Obtained results contradict with the findings of previous studies on temperature trends, which indicate the need for reassessment of climatic trends in Pakistan using the MMK test to understand the anthropogenic impacts of climate change.

Stratospheric Temperature Trends Observed by TIMED/SABER

NASA Astrophysics Data System (ADS)

Xian, T.; Tan, R.

2017-12-01

Trends in the stratospheric temperature are studied based on the temperature profile observation from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER). The spatially trends are evaluated in different time scales ranging from decadal to monthly resolved. The results indicate a signature of BDC acceleration. There are strong warming trends (up to 9 K/decade) in the middle to upper stratosphere in the high latitude spring, summer, and autumn seasons, accompanied by strong cooling trends in the lower stratosphere. Besides, strong warming trends occurs through the whole stratosphere over the Southern Hemisphere, which confirms Antarctic ozone layer healing since 2000. In addition, the results demonstrate a significant warming trends in the middle of tropical stratosphere, which becomes strongest during June-July-August.

Mechanisms underlying recent decadal changes in subpolar North Atlantic Ocean heat content

NASA Astrophysics Data System (ADS)

Piecuch, Christopher G.; Ponte, Rui M.; Little, Christopher M.; Buckley, Martha W.; Fukumori, Ichiro

2017-09-01

The subpolar North Atlantic (SPNA) is subject to strong decadal variability, with implications for surface climate and its predictability. In 2004-2005, SPNA decadal upper ocean and sea-surface temperature trends reversed from warming during 1994-2004 to cooling over 2005-2015. This recent decadal trend reversal in SPNA ocean heat content (OHC) is studied using a physically consistent, observationally constrained global ocean state estimate covering 1992-2015. The estimate's physical consistency facilitates quantitative causal attribution of ocean variations. Closed heat budget diagnostics reveal that the SPNA OHC trend reversal is the result of heat advection by midlatitude ocean circulation. Kinematic decompositions reveal that changes in the deep and intermediate vertical overturning circulation cannot account for the trend reversal, but rather ocean heat transports by horizontal gyre circulations render the primary contributions. The shift in horizontal gyre advection reflects anomalous circulation acting on the mean temperature gradients. Maximum covariance analysis (MCA) reveals strong covariation between the anomalous horizontal gyre circulation and variations in the local wind stress curl, suggestive of a Sverdrup response. Results have implications for decadal predictability.

Interbasin effects of the Indian Ocean on Pacific decadal climate change

NASA Astrophysics Data System (ADS)

Mochizuki, Takashi; Kimoto, Masahide; Watanabe, Masahiro; Chikamoto, Yoshimitsu; Ishii, Masayoshi

2016-07-01

We demonstrate the significant impact of the Indian Ocean on the Pacific climate on decadal timescales by comparing two sets of data assimilation experiments (pacemaker experiments) conducted over recent decades. For the Indian Ocean of an atmosphere-ocean coupled global climate model, we assimilate ocean temperature and salinity anomalies defined as deviations from climatology or as anomalies with the area-averaged changes for the Indian Ocean subtracted. When decadal sea surface temperature (SST) trends are observed to be strong over the Indian Ocean, the equatorial thermocline uniformly deepens, and the model simulates the eastward tendencies of surface wind aloft. Surface winds strongly converge around the maritime continent, and the associated strengthening of the Walker circulation suppresses an increasing trend in the equatorial Pacific SST through ocean thermocline shoaling, similar to common changes associated with seasonal Indian Ocean warming.

Data-driven modeling of surface temperature anomaly and solar activity trends

USGS Publications Warehouse

Friedel, Michael J.

2012-01-01

A novel two-step modeling scheme is used to reconstruct and analyze surface temperature and solar activity data at global, hemispheric, and regional scales. First, the self-organizing map (SOM) technique is used to extend annual modern climate data from the century to millennial scale. The SOM component planes are used to identify and quantify strength of nonlinear relations among modern surface temperature anomalies (<150 years), tropical and extratropical teleconnections, and Palmer Drought Severity Indices (0–2000 years). Cross-validation of global sea and land surface temperature anomalies verifies that the SOM is an unbiased estimator with less uncertainty than the magnitude of anomalies. Second, the quantile modeling of SOM reconstructions reveal trends and periods in surface temperature anomaly and solar activity whose timing agrees with published studies. Temporal features in surface temperature anomalies, such as the Medieval Warm Period, Little Ice Age, and Modern Warming Period, appear at all spatial scales but whose magnitudes increase when moving from ocean to land, from global to regional scales, and from southern to northern regions. Some caveats that apply when interpreting these data are the high-frequency filtering of climate signals based on quantile model selection and increased uncertainty when paleoclimatic data are limited. Even so, all models find the rate and magnitude of Modern Warming Period anomalies to be greater than those during the Medieval Warm Period. Lastly, quantile trends among reconstructed equatorial Pacific temperature profiles support the recent assertion of two primary El Niño Southern Oscillation types. These results demonstrate the efficacy of this alternative modeling approach for reconstructing and interpreting scale-dependent climate variables.

40 CFR 228.13 - Guidelines for ocean disposal site baseline or trend assessment surveys under section 102 of the...

Code of Federal Regulations, 2011 CFR

2011-07-01

... baseline or trend assessment surveys under section 102 of the Act. 228.13 Section 228.13 Protection of... SITES FOR OCEAN DUMPING § 228.13 Guidelines for ocean disposal site baseline or trend assessment surveys under section 102 of the Act. The purpose of a baseline or trend assessment survey is to determine the...

40 CFR 228.13 - Guidelines for ocean disposal site baseline or trend assessment surveys under section 102 of the...

Code of Federal Regulations, 2014 CFR

2014-07-01

... baseline or trend assessment surveys under section 102 of the Act. 228.13 Section 228.13 Protection of... SITES FOR OCEAN DUMPING § 228.13 Guidelines for ocean disposal site baseline or trend assessment surveys under section 102 of the Act. The purpose of a baseline or trend assessment survey is to determine the...

40 CFR 228.13 - Guidelines for ocean disposal site baseline or trend assessment surveys under section 102 of the...

Code of Federal Regulations, 2012 CFR

2012-07-01

... baseline or trend assessment surveys under section 102 of the Act. 228.13 Section 228.13 Protection of... SITES FOR OCEAN DUMPING § 228.13 Guidelines for ocean disposal site baseline or trend assessment surveys under section 102 of the Act. The purpose of a baseline or trend assessment survey is to determine the...

40 CFR 228.13 - Guidelines for ocean disposal site baseline or trend assessment surveys under section 102 of the...

Code of Federal Regulations, 2013 CFR

2013-07-01

... baseline or trend assessment surveys under section 102 of the Act. 228.13 Section 228.13 Protection of... SITES FOR OCEAN DUMPING § 228.13 Guidelines for ocean disposal site baseline or trend assessment surveys under section 102 of the Act. The purpose of a baseline or trend assessment survey is to determine the...

40 CFR 228.13 - Guidelines for ocean disposal site baseline or trend assessment surveys under section 102 of the...

Code of Federal Regulations, 2010 CFR

2010-07-01

... baseline or trend assessment surveys under section 102 of the Act. 228.13 Section 228.13 Protection of... SITES FOR OCEAN DUMPING § 228.13 Guidelines for ocean disposal site baseline or trend assessment surveys under section 102 of the Act. The purpose of a baseline or trend assessment survey is to determine the...

Long-term trends in daily temperature extremes in Iraq

NASA Astrophysics Data System (ADS)

Salman, Saleem A.; Shahid, Shamsuddin; Ismail, Tarmizi; Chung, Eun-Sung; Al-Abadi, Alaa M.

2017-12-01

The existence of long-term persistence (LTP) in hydro-climatic time series can lead to considerable change in significance of trends. Therefore, past findings of climatic trend studies that did not consider LTP became a disputable issue. A study has been conducted to assess the trends in temperature and temperature extremes in Iraq in recent years (1965-2015) using both ordinary Mann-Kendal (MK) test; and the modified Mann-Kendall (m-MK) test, which can differentiate the multi-decadal oscillatory variations from secular trends. Trends in annual and seasonal minimum and maximum temperatures, diurnal temperature range (DTR), and 14 temperature-related extremes were assessed. MK test detected the significant increases in minimum and maximum temperature at all stations, where m-MK test detected at 86% and 80% of all stations, respectively. The temperature in Iraq is increasing 2 to 7 times faster than global temperature rise. The minimum temperature is increasing more (0.48-1.17 °C/decade) than maximum temperature (0.25-1.01 °C/decade). Temperature rise is higher in northern Iraq and in summer. The hot extremes particularly warm nights are increasing all over Iraq at a rate of 2.92-10.69 days/decade, respectively. On the other hand, numbers of cold days are decreasing at some stations at a rate of - 2.65 to - 8.40 days/decade. The use of m-MK test along with MK test confirms the significant increase in temperature and some of the temperature extremes in Iraq. This study suggests that trends in many temperature extremes in the region estimated in previous studies using MK test may be due to natural variability of climate, which empathizes the need for validation of the trends by considering LTP in time series.

Late Holocene Sea Surface Temperature Trends in the Eastern Tropical Pacific

NASA Astrophysics Data System (ADS)

Rustic, G. T.; Koutavas, A.; Marchitto, T. M., Jr.

2015-12-01

The Eastern Tropical Pacific (ETP) is a highly dynamic ocean region capable of exerting influencing on global climate as illustrated by the El Niño-Southern Oscillation (ENSO). The sea surface temperature (SST) history of this region in past millennia is poorly constrained due to the lack of in situ records with appropriate resolution. Here we present a ~2700 year sub-centennially resolved SST reconstruction from Mg/Ca ratios of the planktonic foraminifer Globigerinoides ruber from Galápagos sediments. The ETP SST record exhibits a long-term cooling trend of over 0.2°C/ky that is similar to Northern Hemisphere multi-proxy temperature trends suggesting a common origin, likely due to insolation forcing. The ETP remains in-phase with Northern Hemisphere climate records through the warm Roman Climate Optimum (~0-400CE), cooler Dark Ages Cold Period (~450-850CE), and through the peak warming of the Medieval Climate Anomaly (900-1150 CE) when SST is within error of modern. Following peak MCA, the ETP cooled rapidly and then rebounded at ~1500 CE during the coldest portion of the Little Ice Age. Overall the data suggest an out-of-phase relationship during much of the last millennium, which we attribute to dynamical adjustments consistent with the "dynamical ocean thermostat" mechanism. Further evidence for these dynamical adjustments comes from reconstructions of the east-west zonal SST gradient using existing Mg/Ca SST reconstructions from the western Pacific warm pool. The last millennium has been the most dynamic period over the past 2700 years, with significant (~1 °C) SST variability in the ETP and modulation of the zonal gradient. A combination of dynamical and thermodynamic mechanisms are invoked to explain the region's complex SST history.

The Footprint of the Inter-decadal Pacific Oscillation in Indian Ocean Sea Surface Temperatures

NASA Astrophysics Data System (ADS)

Dong, Lu; Zhou, Tianjun; Dai, Aiguo; Song, Fengfei; Wu, Bo; Chen, Xiaolong

2016-02-01

Superimposed on a pronounced warming trend, the Indian Ocean (IO) sea surface temperatures (SSTs) also show considerable decadal variations that can cause regional climate oscillations around the IO. However, the mechanisms of the IO decadal variability remain unclear. Here we perform numerical experiments using a state-of-the-art, fully coupled climate model in which the external forcings with or without the observed SSTs in the tropical eastern Pacific Ocean (TEP) are applied for 1871-2012. Both the observed timing and magnitude of the IO decadal variations are well reproduced in those experiments with the TEP SSTs prescribed to observations. Although the external forcings account for most of the warming trend, the decadal variability in IO SSTs is dominated by internal variability that is induced by the TEP SSTs, especially the Inter-decadal Pacific Oscillation (IPO). The IPO weakens (enhances) the warming of the external forcings by about 50% over the IO during IPO’s cold (warm) phase, which contributes about 10% to the recent global warming hiatus since 1999. The decadal variability in IO SSTs is modulated by the IPO-induced atmospheric adjustment through changing surface heat fluxes, sea surface height and thermocline depth.

The Footprint of the Inter-decadal Pacific Oscillation in Indian Ocean Sea Surface Temperatures.

PubMed

Dong, Lu; Zhou, Tianjun; Dai, Aiguo; Song, Fengfei; Wu, Bo; Chen, Xiaolong

2016-02-17

Superimposed on a pronounced warming trend, the Indian Ocean (IO) sea surface temperatures (SSTs) also show considerable decadal variations that can cause regional climate oscillations around the IO. However, the mechanisms of the IO decadal variability remain unclear. Here we perform numerical experiments using a state-of-the-art, fully coupled climate model in which the external forcings with or without the observed SSTs in the tropical eastern Pacific Ocean (TEP) are applied for 1871-2012. Both the observed timing and magnitude of the IO decadal variations are well reproduced in those experiments with the TEP SSTs prescribed to observations. Although the external forcings account for most of the warming trend, the decadal variability in IO SSTs is dominated by internal variability that is induced by the TEP SSTs, especially the Inter-decadal Pacific Oscillation (IPO). The IPO weakens (enhances) the warming of the external forcings by about 50% over the IO during IPO's cold (warm) phase, which contributes about 10% to the recent global warming hiatus since 1999. The decadal variability in IO SSTs is modulated by the IPO-induced atmospheric adjustment through changing surface heat fluxes, sea surface height and thermocline depth.

Search for Trends and Periodicities in Inter-hemispheric Sea Surface Temperature Difference

NASA Astrophysics Data System (ADS)

Rajesh, R.; Tiwari, R. K.

2018-02-01

Understanding the role of coupled solar and internal ocean dynamics on hemispheric climate variability is critical to climate modelling. We have analysed here 165 year long annual northern hemispheric (NH) and southern hemispheric (SH) sea surface temperature (SST) data employing spectral and statistical techniques to identify the imprints of solar and ocean-atmospheric processes, if any. We reconstructed the eigen modes of NH-SST and SH-SST to reveal non-linear oscillations superimposed on the monotonic trend. Our analysis reveals that the first eigen mode of NH-SST and SH-SST representing long-term trend of SST variability accounts for 15-23% variance. Interestingly, these components are matching with first eigen mode (99% variance) of the total solar irradiance (TSI) suggesting possible impact of solar activity on long-term SST variation. Furthermore, spectral analysis of SSA reconstructed signal revealed statistically significant periodicities of 63 ± 5, 22 ± 2, 10 ± 1, 7.6, 6.3, 5.2, 4.7, and 4.2 years in both NH-SST and SH-SST data. The major harmonics centred at 63 ± 5, 22 ± 2, and 10 ± 1 years are similar to solar periodicities and hence may represent solar forcing, while the components peaking at around 7.6, 6.3, 5.2, 4.7, and 4.2 years apparently falls in the frequency bands of El-Nino-Southern Oscillations linked to the oceanic internal processes. Our analyses also suggest evidence for the amplitude modulation of 9-11 and 21-22 year solar cycles, respectively, by 104 and 163 years in northern and southern hemispheric SST data. The absence of the above periodic oscillations in CO2 fails to suggest its role on observed inter-hemispheric SST difference. The cross-plot analysis also revealed strong influence of solar activity on linear trend of NH- and SH-SST in addition to small contribution from CO2. Our study concludes that (1) the long-term trends in northern and southern hemispheric SST variability show considerable synchronicity with cyclic

Temperature trend biases

NASA Astrophysics Data System (ADS)

Venema, Victor; Lindau, Ralf

2016-04-01

In an accompanying talk we show that well-homogenized national dataset warm more than temperatures from global collections averaged over the region of common coverage. In this poster we want to present auxiliary work about possible biases in the raw observations and on how well relative statistical homogenization can remove trend biases. There are several possible causes of cooling biases, which have not been studied much. Siting could be an important factor. Urban stations tend to move away from the centre to better locations. Many stations started inside of urban areas and are nowadays more outside. Even for villages the temperature difference between the centre and edge can be 0.5°C. When a city station moves to an airport, which often happened around WWII, this takes the station (largely) out of the urban heat island. During the 20th century the Stevenson screen was established as the dominant thermometer screen. This screen protected the thermometer much better against radiation than earlier designs. Deficits of earlier measurement methods have artificially warmed the temperatures in the 19th century. Newer studies suggest we may have underestimated the size of this bias. Currently we are in a transition to Automatic Weather Stations. The net global effect of this transition is not clear at this moment. Irrigation on average decreases the 2m-temperature by about 1 degree centigrade. At the same time, irrigation has increased significantly during the last century. People preferentially live in irrigated areas and weather stations serve agriculture. Thus it is possible that there is a higher likelihood that weather stations are erected in irrigated areas than elsewhere. In this case irrigation could lead to a spurious cooling trend. In the Parallel Observations Science Team of the International Surface Temperature Initiative (ISTI-POST) we are studying influence of the introduction of Stevenson screens and Automatic Weather Stations using parallel measurements

Closing the Seasonal Ocean Surface Temperature Balance in the Eastern Tropical Oceans from Remote Sensing and Model Reanalyses

NASA Technical Reports Server (NTRS)

Roberts, J. Brent; Clayson, Carol A.

2012-01-01

The Eastern tropical ocean basins are regions of significant atmosphere-ocean interaction and are important to variability across subseasonal to decadal time scales. The numerous physical processes at play in these areas strain the abilities of coupled general circulation models to accurately reproduce observed upper ocean variability. Furthermore, limitations in the observing system of important terms in the surface temperature balance (e.g., turbulent and radiative heat fluxes, advection) introduce uncertainty into the analyses of processes controlling sea surface temperature variability. This study presents recent efforts to close the surface temperature balance through estimation of the terms in the mixed layer temperature budget using state-of-the-art remotely sensed and model-reanalysis derived products. A set of twelve net heat flux estimates constructed using combinations of radiative and turbulent heat flux products - including GEWEX-SRB, ISCCP-SRF, OAFlux, SeaFlux, among several others - are used with estimates of oceanic advection, entrainment, and mixed layer depth variability to investigate the seasonal variability of ocean surface temperatures. Particular emphasis is placed on how well the upper ocean temperature balance is, or is not, closed on these scales using the current generation of observational and model reanalysis products. That is, the magnitudes and spatial variability of residual imbalances are addressed. These residuals are placed into context within the current uncertainties of the surface net heat fluxes and the role of the mixed layer depth variability in scaling the impact of those uncertainties, particularly in the shallow mixed layers of the Eastern tropical ocean basins.

Annual temperature anomaly trends correlate with coral reef trajectory across the Pacific

NASA Astrophysics Data System (ADS)

Riegl, B. M.; Wieters, E.; Bruckner, A.; Purkis, S.

2013-05-01

The future survival of coral reefs depends on the envelope of critical climatic conditions determining the severity of impacts on the ecosystem. While coral health is strongly determined by extreme heat events, that lead to bleaching and often death, chronic "heat loading" may also disadvantage corals by making them more susceptible to, for example, diseases. On the other hand, it has been shown that coral living in hotter areas have higher bleaching thresholds and may be affected by less mortality at extreme events. This level at which heat anomalies lead to coral mortality varies widely across oceans, from ~31 deg C across the Caribbean to ~32 deg C in the Great Barrier Reef to 37.5 deg C in the Persian/Arabian Gulf. Thus, there clearly exists local adaptation and the extremes required to kill reefs strongly vary among regions. This could be be interpreted as suggesting that as long as bleaching temperatures are not reached, increased overall heat content expressed by a positive annual thermal anomaly, might actually foster coral resilience. Is there evidence for or against such an argument? Bleaching events have been occurring worldwide with variable recurrence and variable subsequent recovery. Despite demonstrated adaptation to higher-than-usual mean summer temperatures, reefs in the Arabian Gulf and the Red Sea are on a declining trajectory. This coincides with consistent warming in the region. Mean annual anomalies of ocean temperature (since 1870) and atmospheric temperatures (since 1950) increase throughout the region. Since 1994 (Red Sea) and 1998 (southern Arabian Gulf) all mean annual anomalies have been positive and this period has coincided with repeated, severe bleaching events. In the Eastern Pacific (Galapagos and Easter Island), the trend of mean annual temperature anomalies has been declining and coral cover has been increasing. Thus, trends in coral cover and mean annual anomaly are negatively correlated in both regions. Despite strong impacts

OceanSITES: Sustained Ocean Time Series Observations in the Global Ocean.

NASA Astrophysics Data System (ADS)

Weller, R. A.; Gallage, C.; Send, U.; Lampitt, R. S.; Lukas, R.

2016-02-01

Time series observations at critical or representative locations are an essential element of a global ocean observing system that is unique and complements other approaches to sustained observing. OceanSITES is an international group of oceanographers associated with such time series sites. OceanSITES exists to promote the continuation and extension of ocean time series sites around the globe. It also exists to plan and oversee the global array of sites in order to address the needs of research, climate change detection, operational applications, and policy makers. OceanSITES is a voluntary group that sits as an Action Group of the JCOMM-OPS Data Buoy Cooperation Panel, where JCOMM-OPS is the operational ocean observing oversight group of the Joint Commission on Oceanography and Marine Meteorology of the International Oceanographic Commission and the World Meteorological Organization. The way forward includes working to complete the global array, moving toward multidisciplinary instrumentation on a subset of the sites, and increasing utilization of the time series data, which are freely available from two Global Data Assembly Centers, one at the National Data Buoy Center and one at Coriolis at IFREMER. One recnet OceanSITES initiative and several results from OceanSITES time series sites are presented. The recent initiative was the assembly of a pool of temperature/conductivity recorders fro provision to OceanSITES sites in order to provide deep ocean temperature and salinity time series. Examples from specific sites include: a 15-year record of surface meteorology and air-sea fluxes from off northern Chile that shows evidence of long-term trends in surface forcing; change in upper ocean salinity and stratification in association with regional change in the hydrological cycle can be seen at the Hawaii time series site; results from monitoring Atlantic meridional transport; and results from a European multidisciplinary time series site.

Temperature and ice layer trends in the summer middle atmosphere

NASA Astrophysics Data System (ADS)

Lübken, F.-J.; Berger, U.

2012-04-01

We present results from our LIMA model (Leibniz Institute Middle Atmosphere Model) which nicely reproduces mean conditions of the summer mesopause region and also mean characteristics of ice layers known as noctilucent clouds. LIMA nudges to ECMWF data in the troposphere and lower stratosphere which influences the background conditions in the mesosphere. We study temperature trends in the mesosphere at middle and polar latitudes and compared with temperature trends from satellites, lidar, and phase height observations. For the first time large observed temperature trends in the summer mesosphere can be reproduced and explained by a model. As will be shown, stratospheric ozone has a major impact on temperature trends in the summer mesosphere. The temperature trend is not uniform in time: it is moderate from 1961 (the beginning of our record) until the beginning of the 1980s. Thereafter, temperatures decrease much stronger until the mid 1990s. Thereafter, temperatures are nearly constant or even increase with time. As will be shown, trends in ozone and carbon dioxide explain most of this behavior. Ice layers in the summer mesosphere are very sensitive to background conditions and are therefore considered to be appropriate tracers for long term variations in the middle atmosphere. We use LIMA background conditions to determine ice layer characteristics in the mesopause region. We compare our results with measurements, for example with albedos from the SBUV satellites, and show that we can nicely reproduce observed trends. It turns out that temperature trends are positive (negative) in the upper (lower) part of the ice layer regime. This complicates an interpretation of NLC long term variations in terms of temperature trends.

Patterns and Emerging Trends in Global Ocean Health

PubMed Central

Halpern, Benjamin S.; Longo, Catherine; Lowndes, Julia S. Stewart; Best, Benjamin D.; Frazier, Melanie; Katona, Steven K.; Kleisner, Kristin M.; Rosenberg, Andrew A.; Scarborough, Courtney; Selig, Elizabeth R.

2015-01-01

International and regional policies aimed at managing ocean ecosystem health need quantitative and comprehensive indices to synthesize information from a variety of sources, consistently measure progress, and communicate with key constituencies and the public. Here we present the second annual global assessment of the Ocean Health Index, reporting current scores and annual changes since 2012, recalculated using updated methods and data based on the best available science, for 221 coastal countries and territories. The Index measures performance of ten societal goals for healthy oceans on a quantitative scale of increasing health from 0 to 100, and combines these scores into a single Index score, for each country and globally. The global Index score improved one point (from 67 to 68), while many country-level Index and goal scores had larger changes. Per-country Index scores ranged from 41–95 and, on average, improved by 0.06 points (range -8 to +12). Globally, average scores increased for individual goals by as much as 6.5 points (coastal economies) and decreased by as much as 1.2 points (natural products). Annual updates of the Index, even when not all input data have been updated, provide valuable information to scientists, policy makers, and resource managers because patterns and trends can emerge from the data that have been updated. Changes of even a few points indicate potential successes (when scores increase) that merit recognition, or concerns (when scores decrease) that may require mitigative action, with changes of more than 10–20 points representing large shifts that deserve greater attention. Goal scores showed remarkably little covariance across regions, indicating low redundancy in the Index, such that each goal delivers information about a different facet of ocean health. Together these scores provide a snapshot of global ocean health and suggest where countries have made progress and where a need for further improvement exists. PMID:25774678

Along - Strike Analysis of Contemporary Ocean Temperature Change on the Cascadia Margin and Implications to Upper Slope Hydrate Instability

NASA Astrophysics Data System (ADS)

Phrampus, B.; Harris, R. N.; Trehu, A. M.; Embley, R. W.; Merle, S. G.

2017-12-01

Gas hydrates are found globally on continental margins and due to the large amount of sequestered carbon in hydrate reservoirs, whether these deposits are dynamic or stable has significant implications for slope stability, ocean/atmosphere carbon budget, and deep-water energy exploration. Recent studies indicate that upper slope hydrate degradation may be relatively widespread on passive margins due to recent ocean temperature warming between 0.012 and 0.033 °C/yr (e.g. Svalbard, North Alaska, and US Atlantic margin). However, the potential and breadth of warming induced hydrate instability remains contentious based on multiple observations including: 1) seep locations not consistent with locations of hydrate dissociation, 2) a lack of hydrate in regions of warming, and 3) evidence for long-lived seepage in regions associated with contemporary warming-induced hydrate dissociation. At the Cascadia margin, a recent study suggests that contemporary warming of intermediate water intersects the hydrate stability zone leading to hydrate dissociation that feeds upper slope seeps. Here, we provide a systematic analysis of along-strike variations in hydrate distribution along the Cascadia margin combined with a multivariable regression of ocean temperatures to characterize the potential of upper slope hydrate instability. Preliminary seep locations reveal upper slope seeps and observed regions of hydrate are correlated spatially between 42.5 and 48.0 °N, outside this region there is a dearth of identified upper slope hydrate and seeps. Between 44.5 and 48.0 °N a contemporary warming trend is as large as 0.006 °C/yr and is collocated with upper slope hydrate and gas seepage. This warming rate is relatively small, 2-5x smaller than warming trends identified in the Arctic where temperature induced hydrate instability remains uncertain. Additionally, we identify a region between 42.5 and 44.5 °N with collocated upper slope seepage and hydrate but no evidence of ocean

Glacial ocean circulation and stratification explained by reduced atmospheric temperature.

PubMed

Jansen, Malte F

2017-01-03

Earth's climate has undergone dramatic shifts between glacial and interglacial time periods, with high-latitude temperature changes on the order of 5-10 °C. These climatic shifts have been associated with major rearrangements in the deep ocean circulation and stratification, which have likely played an important role in the observed atmospheric carbon dioxide swings by affecting the partitioning of carbon between the atmosphere and the ocean. The mechanisms by which the deep ocean circulation changed, however, are still unclear and represent a major challenge to our understanding of glacial climates. This study shows that various inferred changes in the deep ocean circulation and stratification between glacial and interglacial climates can be interpreted as a direct consequence of atmospheric temperature differences. Colder atmospheric temperatures lead to increased sea ice cover and formation rate around Antarctica. The associated enhanced brine rejection leads to a strongly increased deep ocean stratification, consistent with high abyssal salinities inferred for the last glacial maximum. The increased stratification goes together with a weakening and shoaling of the interhemispheric overturning circulation, again consistent with proxy evidence for the last glacial. The shallower interhemispheric overturning circulation makes room for slowly moving water of Antarctic origin, which explains the observed middepth radiocarbon age maximum and may play an important role in ocean carbon storage.

Spread in the magnitude of climate model interdecadal global temperature variability traced to disagreements over high-latitude oceans

NASA Astrophysics Data System (ADS)

Brown, Patrick T.; Li, Wenhong; Jiang, Jonathan H.; Su, Hui

2016-12-01

Unforced variability in global mean surface air temperature can obscure or exaggerate global warming on interdecadal time scales; thus, understanding both the magnitude and generating mechanisms of such variability is of critical importance for both attribution studies as well as decadal climate prediction. Coupled atmosphere-ocean general circulation models (climate models) simulate a wide range of magnitudes of unforced interdecadal variability in global mean surface air temperature (UITglobal), hampering efforts to quantify the influence of UITglobal on contemporary global temperature trends. Recently, a preliminary consensus has emerged that unforced interdecadal variability in local surface temperatures (UITlocal) over the tropical Pacific Ocean is particularly influential on UITglobal. Therefore, a reasonable hypothesis might be that the large spread in the magnitude of UITglobal across climate models can be explained by the spread in the magnitude of simulated tropical Pacific UITlocal. Here we show that this hypothesis is mostly false. Instead, the spread in the magnitude of UITglobal is linked much more strongly to the spread in the magnitude of UITlocal over high-latitude regions characterized by significant variability in oceanic convection, sea ice concentration, and energy flux at both the surface and the top of the atmosphere. Thus, efforts to constrain the climate model produced range of UITglobal magnitude would be best served by focusing on the simulation of air-sea interaction at high latitudes.

Comparison of Two Global Ocean Reanalyses, NRL Global Ocean Forecast System (GOFS) and U. Maryland Simple Ocean Data Assimilation (SODA)

NASA Astrophysics Data System (ADS)

Richman, J. G.; Shriver, J. F.; Metzger, E. J.; Hogan, P. J.; Smedstad, O. M.

2017-12-01

The Oceanography Division of the Naval Research Laboratory recently completed a 23-year (1993-2015) coupled ocean-sea ice reanalysis forced by NCEP CFS reanalysis fluxes. The reanalysis uses the Global Ocean Forecast System (GOFS) framework of the HYbrid Coordinate Ocean Model (HYCOM) and the Los Alamos Community Ice CodE (CICE) and the Navy Coupled Ocean Data Assimilation 3D Var system (NCODA). The ocean model has 41 layers and an equatorial resolution of 0.08° (8.8 km) on a tri-polar grid with the sea ice model on the same grid that reduces to 3.5 km at the North Pole. Sea surface temperature (SST), sea surface height (SSH) and temperature-salinity profile data are assimilated into the ocean every day. The SSH anomalies are converted into synthetic profiles of temperature and salinity prior to assimilation. Incremental analysis updating of geostrophically balanced increments is performed over a 6-hour insertion window. Sea ice concentration is assimilated into the sea ice model every day. Following the lead of the Ocean Reanalysis Intercomparison Project (ORA-IP), the monthly mean upper ocean heat and salt content from the surface to 300 m, 700m and 1500 m, the mixed layer depth, the depth of the 20°C isotherm, the steric sea surface height and the Atlantic Meridional Overturning Circulation for the GOFS reanalysis and the Simple Ocean Data Assimilation (SODA 3.3.1) eddy-permitting reanalysis have been compared on a global uniform 0.5° grid. The differences between the two ocean reanalyses in heat and salt content increase with increasing integration depth. Globally, GOFS trends to be colder than SODA at all depth. Warming trends are observed at all depths over the 23 year period. The correlation of the upper ocean heat content is significant above 700 m. Prior to 2004, differences in the data assimilated lead to larger biases. The GOFS reanalysis assimilates SSH as profile data, while SODA doesn't. Large differences are found in the Western Boundary Currents

The footprint of the inter-decadal Pacific oscillation in Indian Ocean sea surface temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Lu; Zhou, Tianjun; Dai, Aiguo

Superimposed on a pronounced warming trend, the Indian Ocean (IO) sea surface temperatures (SSTs) also show considerable decadal variations that can cause regional climate oscillations around the IO. However, the mechanisms of the IO decadal variability remain unclear. Here we perform numerical experiments using a state-of-the-art, fully coupled climate model in which the external forcings with or without the observed SSTs in the tropical eastern Pacific Ocean (TEP) are applied for 1871–2012. Both the observed timing and magnitude of the IO decadal variations are well reproduced in those experiments with the TEP SSTs prescribed to observations. Although the external forcingsmore » account for most of the warming trend, the decadal variability in IO SSTs is dominated by internal variability that is induced by the TEP SSTs, especially the Inter-decadal Pacific Oscillation (IPO). The IPO weakens (enhances) the warming of the external forcings by about 50% over the IO during IPO’s cold (warm) phase, which contributes about 10% to the recent global warming hiatus since 1999. As a result, the decadal variability in IO SSTs is modulated by the IPO-induced atmospheric adjustment through changing surface heat fluxes, sea surface height and thermocline depth.« less

The footprint of the inter-decadal Pacific oscillation in Indian Ocean sea surface temperatures

DOE PAGES

Dong, Lu; Zhou, Tianjun; Dai, Aiguo; ...

2016-02-17

Superimposed on a pronounced warming trend, the Indian Ocean (IO) sea surface temperatures (SSTs) also show considerable decadal variations that can cause regional climate oscillations around the IO. However, the mechanisms of the IO decadal variability remain unclear. Here we perform numerical experiments using a state-of-the-art, fully coupled climate model in which the external forcings with or without the observed SSTs in the tropical eastern Pacific Ocean (TEP) are applied for 1871–2012. Both the observed timing and magnitude of the IO decadal variations are well reproduced in those experiments with the TEP SSTs prescribed to observations. Although the external forcingsmore » account for most of the warming trend, the decadal variability in IO SSTs is dominated by internal variability that is induced by the TEP SSTs, especially the Inter-decadal Pacific Oscillation (IPO). The IPO weakens (enhances) the warming of the external forcings by about 50% over the IO during IPO’s cold (warm) phase, which contributes about 10% to the recent global warming hiatus since 1999. As a result, the decadal variability in IO SSTs is modulated by the IPO-induced atmospheric adjustment through changing surface heat fluxes, sea surface height and thermocline depth.« less

Differences between near-surface equivalent temperature and temperature trends for the Eastern United States. Equivalent temperature as an alternative measure of heat content

USGS Publications Warehouse

Davey, C.A.; Pielke, R.A.; Gallo, K.P.

2006-01-01

There is currently much attention being given to the observed increase in near-surface air temperatures during the last century. The proper investigation of heating trends, however, requires that we include surface heat content to monitor this aspect of the climate system. Changes in heat content of the Earth's climate are not fully described by temperature alone. Moist enthalpy or, alternatively, equivalent temperature, is more sensitive to surface vegetation properties than is air temperature and therefore more accurately depicts surface heating trends. The microclimates evident at many surface observation sites highlight the influence of land surface characteristics on local surface heating trends. Temperature and equivalent temperature trend differences from 1982-1997 are examined for surface sites in the Eastern U.S. Overall trend differences at the surface indicate equivalent temperature trends are relatively warmer than temperature trends in the Eastern U.S. Seasonally, equivalent temperature trends are relatively warmer than temperature trends in winter and are relatively cooler in the fall. These patterns, however, vary widely from site to site, so local microclimate is very important. ?? 2006 Elsevier B.V. All rights reserved.

Recent Development on the NOAA's Global Surface Temperature Dataset

NASA Astrophysics Data System (ADS)

Zhang, H. M.; Huang, B.; Boyer, T.; Lawrimore, J. H.; Menne, M. J.; Rennie, J.

2016-12-01

Global Surface Temperature (GST) is one of the most widely used indicators for climate trend and extreme analyses. A widely used GST dataset is the NOAA merged land-ocean surface temperature dataset known as NOAAGlobalTemp (formerly MLOST). The NOAAGlobalTemp had recently been updated from version 3.5.4 to version 4. The update includes a significant improvement in the ocean surface component (Extended Reconstructed Sea Surface Temperature or ERSST, from version 3b to version 4) which resulted in an increased temperature trends in recent decades. Since then, advancements in both the ocean component (ERSST) and land component (GHCN-Monthly) have been made, including the inclusion of Argo float SSTs and expanded EOT modes in ERSST, and the use of ISTI databank in GHCN-Monthly. In this presentation, we describe the impact of those improvements on the merged global temperature dataset, in terms of global trends and other aspects.

Western Arctic Ocean temperature variability during the last 8000 years

USGS Publications Warehouse

Farmer, Jesse R.; Cronin, Thomas M.; De Vernal, Anne; Dwyer, Gary S.; Keigwin, Loyd D.; Thunell, Robert C.

2011-01-01

We reconstructed subsurface (∼200–400 m) ocean temperature and sea-ice cover in the Canada Basin, western Arctic Ocean from foraminiferal δ18O, ostracode Mg/Ca ratios, and dinocyst assemblages from two sediment core records covering the last 8000 years. Results show mean temperature varied from −1 to 0.5°C and −0.5 to 1.5°C at 203 and 369 m water depths, respectively. Centennial-scale warm periods in subsurface temperature records correspond to reductions in summer sea-ice cover inferred from dinocyst assemblages around 6.5 ka, 3.5 ka, 1.8 ka and during the 15th century Common Era. These changes may reflect centennial changes in the temperature and/or strength of inflowing Atlantic Layer water originating in the eastern Arctic Ocean. By comparison, the 0.5 to 0.7°C warm temperature anomaly identified in oceanographic records from the Atlantic Layer of the Canada Basin exceeded reconstructed Atlantic Layer temperatures for the last 1200 years by about 0.5°C.

Consensuses and discrepancies of basin-scale ocean heat content changes in different ocean analyses

NASA Astrophysics Data System (ADS)

Wang, Gongjie; Cheng, Lijing; Abraham, John; Li, Chongyin

2018-04-01

Inconsistent global/basin ocean heat content (OHC) changes were found in different ocean subsurface temperature analyses, especially in recent studies related to the slowdown in global surface temperature rise. This finding challenges the reliability of the ocean subsurface temperature analyses and motivates a more comprehensive inter-comparison between the analyses. Here we compare the OHC changes in three ocean analyses (Ishii, EN4 and IAP) to investigate the uncertainty in OHC in four major ocean basins from decadal to multi-decadal scales. First, all products show an increase of OHC since 1970 in each ocean basin revealing a robust warming, although the warming rates are not identical. The geographical patterns, the key modes and the vertical structure of OHC changes are consistent among the three datasets, implying that the main OHC variabilities can be robustly represented. However, large discrepancies are found in the percentage of basinal ocean heating related to the global ocean, with the largest differences in the Pacific and Southern Ocean. Meanwhile, we find a large discrepancy of ocean heat storage in different layers, especially within 300-700 m in the Pacific and Southern Oceans. Furthermore, the near surface analysis of Ishii and IAP are consistent with sea surface temperature (SST) products, but EN4 is found to underestimate the long-term trend. Compared with ocean heat storage derived from the atmospheric budget equation, all products show consistent seasonal cycles of OHC in the upper 1500 m especially during 2008 to 2012. Overall, our analyses further the understanding of the observed OHC variations, and we recommend a careful quantification of errors in the ocean analyses.

Decadal trends of the upper ocean salinity in the tropical Indo-Pacific since mid-1990s

NASA Astrophysics Data System (ADS)

DU, Y.; Zhang, Y.

2016-02-01

A contrasting trend pattern of sea surface salinity (SSS) between the western tropical Pacific (WTP) and the southeastern tropical Indian Ocean (SETIO) is observed during 2004-2013, with significant salinity increase in the WTP and freshening in the SETIO. In this study, we show that increased precipitation around the Maritime Continent (MC), decreased precipitation in the western-central tropical Pacific, and ocean advection processes contribute to the salinity trends in the region. From a longer historical record, these salinity trends started in the mid-1990s, a few years before the Global Warming Hiatus from 1998 to present. The salinity trends are associated a strengthening trend of the Walker Circulation over the tropical Indo-Pacific, which have reversed the long-term salinity changes in the tropical Indo-Pacific as a consequence of global warming. Understanding decadal variations of SSS in the tropical Indo-Pacific will better inform on how the tropical hydrological cycle will be affected by the natural variability and a warming climate.

Decadal trends of the upper ocean salinity in the tropical Indo-Pacific since mid-1990s

NASA Astrophysics Data System (ADS)

Du, Yan; Zhang, Yuhong; Feng, Ming; Wang, Tianyu; Zhang, Ningning; Wijffels, Susan

2015-11-01

A contrasting trend pattern of sea surface salinity (SSS) between the western tropical Pacific (WTP) and the southeastern tropical Indian Ocean (SETIO) is observed during 2004-2013, with significant salinity increase in the WTP and freshening in the SETIO. In this study, we show that increased precipitation around the Maritime Continent (MC), decreased precipitation in the western-central tropical Pacific, and ocean advection processes contribute to the salinity trends in the region. From a longer historical record, these salinity trends started in the mid-1990s, a few years before the Global Warming Hiatus from 1998 to present. The salinity trends are associated a strengthening trend of the Walker Circulation over the tropical Indo-Pacific, which have reversed the long-term salinity changes in the tropical Indo-Pacific as a consequence of global warming. Understanding decadal variations of SSS in the tropical Indo-Pacific will better inform on how the tropical hydrological cycle will be affected by the natural variability and a warming climate.

Decadal trends of the upper ocean salinity in the tropical Indo-Pacific since mid-1990s

PubMed Central

Du, Yan; Zhang, Yuhong; Feng, Ming; Wang, Tianyu; Zhang, Ningning; Wijffels, Susan

2015-01-01

A contrasting trend pattern of sea surface salinity (SSS) between the western tropical Pacific (WTP) and the southeastern tropical Indian Ocean (SETIO) is observed during 2004–2013, with significant salinity increase in the WTP and freshening in the SETIO. In this study, we show that increased precipitation around the Maritime Continent (MC), decreased precipitation in the western-central tropical Pacific, and ocean advection processes contribute to the salinity trends in the region. From a longer historical record, these salinity trends started in the mid-1990s, a few years before the Global Warming Hiatus from 1998 to present. The salinity trends are associated a strengthening trend of the Walker Circulation over the tropical Indo-Pacific, which have reversed the long-term salinity changes in the tropical Indo-Pacific as a consequence of global warming. Understanding decadal variations of SSS in the tropical Indo-Pacific will better inform on how the tropical hydrological cycle will be affected by the natural variability and a warming climate. PMID:26522168

Decadal trends of the upper ocean salinity in the tropical Indo-Pacific since mid-1990s.

PubMed

Du, Yan; Zhang, Yuhong; Feng, Ming; Wang, Tianyu; Zhang, Ningning; Wijffels, Susan

2015-11-02

A contrasting trend pattern of sea surface salinity (SSS) between the western tropical Pacific (WTP) and the southeastern tropical Indian Ocean (SETIO) is observed during 2004-2013, with significant salinity increase in the WTP and freshening in the SETIO. In this study, we show that increased precipitation around the Maritime Continent (MC), decreased precipitation in the western-central tropical Pacific, and ocean advection processes contribute to the salinity trends in the region. From a longer historical record, these salinity trends started in the mid-1990s, a few years before the Global Warming Hiatus from 1998 to present. The salinity trends are associated a strengthening trend of the Walker Circulation over the tropical Indo-Pacific, which have reversed the long-term salinity changes in the tropical Indo-Pacific as a consequence of global warming. Understanding decadal variations of SSS in the tropical Indo-Pacific will better inform on how the tropical hydrological cycle will be affected by the natural variability and a warming climate.

Combined ocean acidification and low temperature stressors cause coral mortality

NASA Astrophysics Data System (ADS)

Kavousi, Javid; Parkinson, John Everett; Nakamura, Takashi

2016-09-01

Oceans are predicted to become more acidic and experience more temperature variability—both hot and cold—as climate changes. Ocean acidification negatively impacts reef-building corals, especially when interacting with other stressors such as elevated temperature. However, the effects of combined acidification and low temperature stress have yet to be assessed. Here, we exposed nubbins of the scleractinian coral Montipora digitata to ecologically relevant acidic, cold, or combined stress for 2 weeks. Coral nubbins exhibited 100% survival in isolated acidic and cold treatments, but ~30% mortality under combined conditions. These results provide further evidence that coupled stressors have an interactive effect on coral physiology, and reveal that corals in colder environments are also susceptible to the deleterious impacts of coupled ocean acidification and thermal stress.

Trends in rainfall and temperature extremes in Morocco

NASA Astrophysics Data System (ADS)

Khomsi, K.; Mahe, G.; Tramblay, Y.; Sinan, M.; Snoussi, M.

2015-02-01

In Morocco, socioeconomic fields are vulnerable to weather extreme events. This work aims to analyze the frequency and the trends of temperature and rainfall extreme events in two contrasted Moroccan regions (the Tensift in the semi-arid South, and the Bouregreg in the sub-humid North), during the second half of the 20th century. This study considers long time series of daily extreme temperatures and rainfall, recorded in the stations of Marrakech and Safi for the Tensift region, and Kasba-Tadla and Rabat-Sale for the Bouregreg region, data from four other stations (Tanger, Fes, Agadir and Ouarzazate) from outside the regions were added. Extremes are defined by using as thresholds the 1st, 5th, 90th, 95th, and 99th percentiles. Results show upward trends in maximum and minimum temperatures of both regions and no generalized trends in rainfall amounts. Changes in cold events are larger than those for warm events, and the number of very cold events decrease significantly in the whole studied area. The southern region is the most affected with the changes of the temperature regime. Most of the trends found in rainfall heavy events are positive with weak magnitudes even though no statistically significant generalized trends could be identified during both seasons.

Analysis of trends in climate, streamflow, and stream temperature in north coastal California

USGS Publications Warehouse

Madej, Mary Ann; Medley, C. Nicholas; Patterson, Glenn; Parker, Melanie J.

2011-01-01

As part of a broader project analyzing trends in climate, streamflow, vegetation, salmon, and ocean conditions in northern California national park units, we compiled average monthly air temperature and precipitation data from 73 climate stations, streamflow data from 21 river gaging stations, and limited stream temperature data from salmon-bearing rivers in north coastal California. Many climate stations show a statistically significant increase in both average maximum and average minimum air temperature in early fall and midwinter during the last century. Concurrently, average September precipitation has decreased. In many coastal rivers, summer low flow has decreased and summer stream temperatures have increased, which affects summer rearing habitat for salmonids. Nevertheless, because vegetative cover has also changed during this time period, we cannot ascribe streamflow changes to climate change without first assessing water budgets. Although shifts in the timing of the centroid of runoff have been documented in snowmelt-dominated watersheds in the western United States, this was not the case in lower elevation coastal rivers analyzed in this study.

Glacial ocean circulation and stratification explained by reduced atmospheric temperature

NASA Astrophysics Data System (ADS)

Jansen, Malte F.

2017-01-01

Earth’s climate has undergone dramatic shifts between glacial and interglacial time periods, with high-latitude temperature changes on the order of 5-10 °C. These climatic shifts have been associated with major rearrangements in the deep ocean circulation and stratification, which have likely played an important role in the observed atmospheric carbon dioxide swings by affecting the partitioning of carbon between the atmosphere and the ocean. The mechanisms by which the deep ocean circulation changed, however, are still unclear and represent a major challenge to our understanding of glacial climates. This study shows that various inferred changes in the deep ocean circulation and stratification between glacial and interglacial climates can be interpreted as a direct consequence of atmospheric temperature differences. Colder atmospheric temperatures lead to increased sea ice cover and formation rate around Antarctica. The associated enhanced brine rejection leads to a strongly increased deep ocean stratification, consistent with high abyssal salinities inferred for the last glacial maximum. The increased stratification goes together with a weakening and shoaling of the interhemispheric overturning circulation, again consistent with proxy evidence for the last glacial. The shallower interhemispheric overturning circulation makes room for slowly moving water of Antarctic origin, which explains the observed middepth radiocarbon age maximum and may play an important role in ocean carbon storage.

Glacial ocean circulation and stratification explained by reduced atmospheric temperature

PubMed Central

Jansen, Malte F.

2017-01-01

Earth’s climate has undergone dramatic shifts between glacial and interglacial time periods, with high-latitude temperature changes on the order of 5–10 °C. These climatic shifts have been associated with major rearrangements in the deep ocean circulation and stratification, which have likely played an important role in the observed atmospheric carbon dioxide swings by affecting the partitioning of carbon between the atmosphere and the ocean. The mechanisms by which the deep ocean circulation changed, however, are still unclear and represent a major challenge to our understanding of glacial climates. This study shows that various inferred changes in the deep ocean circulation and stratification between glacial and interglacial climates can be interpreted as a direct consequence of atmospheric temperature differences. Colder atmospheric temperatures lead to increased sea ice cover and formation rate around Antarctica. The associated enhanced brine rejection leads to a strongly increased deep ocean stratification, consistent with high abyssal salinities inferred for the last glacial maximum. The increased stratification goes together with a weakening and shoaling of the interhemispheric overturning circulation, again consistent with proxy evidence for the last glacial. The shallower interhemispheric overturning circulation makes room for slowly moving water of Antarctic origin, which explains the observed middepth radiocarbon age maximum and may play an important role in ocean carbon storage. PMID:27994158

Wet-bulb, dew point, and air temperature trends in Spain

NASA Astrophysics Data System (ADS)

Moratiel, R.; Soriano, B.; Centeno, A.; Spano, D.; Snyder, R. L.

2017-10-01

This study analyses trends of mean ( T m), maximum ( T x), minimum ( T n), dew point ( T d), and wet-bulb temperatures ( T w) on an annual, seasonal, and monthly time scale over Spain during the period 1981-2010. The main purpose was to determine how temperature and humidity changes are impacting on T w, which is probably a better measure of climate change than temperature alone. In this study, 43 weather stations were used to detect data trends using the nonparametric Mann-Kendall test and the Sen method to estimate the slope of trends. Significant linear trends observed for T m, T x, and T n versus year were 56, 58, and 47 % of the weather stations, respectively, with temperature ranges between 0.2 and 0.4 °C per decade. The months with bigger trends were April, May, June, and July with the highest trend for T x. The spatial behaviour of T d and T w was variable, with various locations showing trends from -0.6 to +0.3 °C per decade for T d and from -0.4 to +0.5 °C per decade for T w. Both T d and T w showed negative trends for July, August, September, November, and December. Comparing the trends versus time of each variable versus each of the other variables exhibited poor relationships, which means you cannot predict the trend of one variable from the trend of another variable. The trend of T x was not related to the trend of T n. The trends of T x, T m, and T n versus time were unrelated to the trends versus time of either T d or T w. The trend of T w showed a high coefficient of determination with the trend of T d with an annual value of R 2 = 0.86. Therefore, the T w trend is more related to changes in humidity than temperature.

The salinity, temperature, and delta18O of the glacial deep ocean.

PubMed

Adkins, Jess F; McIntyre, Katherine; Schrag, Daniel P

2002-11-29

We use pore fluid measurements of the chloride concentration and the oxygen isotopic composition from Ocean Drilling Program cores to reconstruct salinity and temperature of the deep ocean during the Last Glacial Maximum (LGM). Our data show that the temperatures of the deep Pacific, Southern, and Atlantic oceans during the LGM were relatively homogeneous and within error of the freezing point of seawater at the ocean's surface. Our chloride data show that the glacial stratification was dominated by salinity variations, in contrast with the modern ocean, for which temperature plays a primary role. During the LGM the Southern Ocean contained the saltiest water in the deep ocean. This reversal of the modern salinity contrast between the North and South Atlantic implies that the freshwater budget at the poles must have been quite different. A strict conversion of mean salinity at the LGM to equivalent sea-level change yields a value in excess of 140 meters. However, the storage of fresh water in ice shelves and/or groundwater reserves implies that glacial salinity is a poor predictor of mean sea level.

Trends in summer bottom-water temperatures on the northern Gulf of Mexico continental shelf from 1985 to 2015.

PubMed

Turner, R Eugene; Rabalais, Nancy N; Justić, Dubravko

2017-01-01

We quantified trends in the 1985 to 2015 summer bottom-water temperature on the northern Gulf of Mexico (nGOM) continental shelf for data collected at 88 stations with depths ranging from 3 to 63 m. The analysis was supplemented with monthly data collected from 1963 to 1965 in the same area. The seasonal summer peak in average bottom-water temperature varied concurrently with air temperature, but with a 2- to 5-month lag. The summer bottom-water temperature declined gradually with depth from 30 oC at stations closest to the shore, to 20 oC at the offshore edge of the study area, and increased an average 0.051 oC y-1 between1963 and 2015. The bottom-water warming in summer for all stations was 1.9 times faster compared to the rise in local summer air temperatures, and 6.4 times faster than the concurrent increase in annual global ocean sea surface temperatures. The annual rise in average summer bottom-water temperatures on the subtropical nGOM continental shelf is comparable to the few published temperature trend estimates from colder environments. These recent changes in the heat storage on the nGOM continental shelf will affect oxygen and carbon cycling, spatial distribution of fish and shrimp, and overall species diversity.

Chemical trends in ocean islands explained by plume–slab interaction

NASA Astrophysics Data System (ADS)

Dannberg, Juliane; Gassmöller, Rene

2018-04-01

Earth's surface shows many features, of which the genesis can be understood only through their connection with processes in Earth's deep interior. Recent studies indicate that spatial geochemical patterns at oceanic islands correspond to structures in the lowermost mantle inferred from seismic tomographic models. This suggests that hot, buoyant upwellings can carry chemical heterogeneities from the deep lower mantle toward the surface, providing a window to the composition of the lowermost mantle. The exact nature of this link between surface and deep Earth remains debated and poorly understood. Using computational models, we show that subducted slabs interacting with dense thermochemical piles can trigger the ascent of hot plumes that inherit chemical gradients present in the lowermost mantle. We identify two key factors controlling this process: (i) If slabs induce strong lower-mantle flow toward the edges of these piles where plumes rise, the pile-facing side of the plume preferentially samples material originating from the pile, and bilaterally asymmetric chemical zoning develops. (ii) The composition of the melt produced reflects this bilateral zoning if the overlying plate moves roughly perpendicular to the chemical gradient in the plume conduit. Our results explain some of the observed geochemical trends of oceanic islands and provide insights into how these trends may originate.

Observed Trends in West Coast Atmospheric River Temperatures

NASA Astrophysics Data System (ADS)

Gonzales, K. R.; Swain, D. L.; Barnes, E. A.; Diffenbaugh, N. S.

2017-12-01

Understanding the changing characteristics of atmospheric rivers (ARs) in a warming climate is critical in light of their importance in generating precipitation and creating the potential for flood and geophysical hazards. Numerous changes to the characteristics of ARs under the influence of a changing climate have been documented or hypothesized; one simple hypothesis is that AR precipitation will occur at increasingly warm temperatures, potentially altering the critical rain/snow balance in snowpack-dependent watersheds and causing precipitation at higher elevations to fall as rain rather than snow. Not only would warmer, primarily rain-producing ARs greatly affect snow accumulation, but they might also increase the intensity of runoff, the potential for flooding, and the occurrence of rain-on-snow events. Since the West Coast of North America relies heavily on ARs as a source of precipitation and snowpack accumulation, these regions may be profoundly affected by changes in AR temperatures and associated impacts. Using a catalog of ARs encompassing 1979-2014 and ERA-Interim reanalysis, we assess whether detectable trends exist in cool season AR temperatures over the Pacific Coast states of California, Oregon, and Washington. We define AR temperature by the mean temperature of the air mass between 1000 hPa and 750 hPa, and compare AR temperature trends to background temperature trends over the same period. We find overall AR warming over this period and particularly robust warming in March ARs coincident with an apparent poleward shift in March AR frequency. Further analysis suggests that warmer ARs have higher rates of warming than cooler ARs. AR temperature trends generally scale with background temperature trends, although some regions exhibit a near one-to-one relationship while others are largely uncorrelated. The observed warming of ARs making landfall on the West Coast may have potentially significant implications for rain vs. snow at higher elevations, the

Timescales for determining temperature and dissolved oxygen trends in the Long Island Sound (LIS) estuary

NASA Astrophysics Data System (ADS)

Staniec, Allison; Vlahos, Penny

2017-12-01

Long-term time series represent a critical part of the oceanographic community's efforts to discern natural and anthropogenically forced variations in the environment. They provide regular measurements of climate relevant indicators including temperature, oxygen concentrations, and salinity. When evaluating time series, it is essential to isolate long-term trends from autocorrelation in data and noise due to natural variability. Herein we apply a statistical approach, well-established in atmospheric time series, to key parameters in the U.S. east coast's Long Island Sound estuary (LIS). Analysis shows that the LIS time series (established in the early 1990s) is sufficiently long to detect significant trends in physical-chemical parameters including temperature (T) and dissolved oxygen (DO). Over the last two decades, overall (combined surface and deep) LIS T has increased at an average rate of 0.08 ± 0.03 °C yr-1 while overall DO has dropped at an average rate of 0.03 ± 0.01 mg L-1yr-1 since 1994 at the 95% confidence level. This trend is notably faster than the global open ocean T trend (0.01 °C yr-1), as might be expected for a shallower estuarine system. T and DO trends were always significant for the existing time series using four month data increments. Rates of change of DO and T in LIS are strongly correlated and the rate of decrease of DO concentrations is consistent with the expected reduced solubility of DO at these higher temperatures. Thus, changes in T alone, across decadal timescales can account for between 33 and 100% of the observed decrease in DO. This has significant implications for other dissolved gases and the long-term management of LIS hypoxia.

Using a Very Large Ensemble to Examine the Role of the Ocean in Recent Warming Trends.

NASA Astrophysics Data System (ADS)

Sparrow, S. N.; Millar, R.; Otto, A.; Yamazaki, K.; Allen, M. R.

2014-12-01

Results from a very large (~10,000 member) perturbed physics and perturbed initial condition ensemble are presented for the period 1980 to present. A set of model versions that can shadow recent surface and upper ocean observations are identified and the range of uncertainty in the Atlantic Meridional Overturning Circulation (AMOC) assessed. This experiment uses the Met Office Hadley Centre Coupled Model version 3 (HadCM3), a coupled model with fully dynamic atmosphere and ocean components as part of the climateprediction.net distributive computing project. Parameters are selected so that the model has good top of atmosphere radiative balance and simulations are run without flux adjustments that "nudge" the climate towards a realistic state, but have an adverse effect on important ocean processes. This ensemble provides scientific insights on the possible role of the AMOC, among other factors, in climate trends, or lack thereof, over the past 20 years. This ensemble is also used to explore how the occurrence of hiatus events of different durations varies for models with different transient climate response (TCR). We show that models with a higher TCR are less likely to produce a 15-year warming hiatus in global surface temperature than those with a lower TCR.

Trends in mean and extreme temperatures over Ibadan, Southwest Nigeria

NASA Astrophysics Data System (ADS)

Abatan, Abayomi A.; Osayomi, Tolulope; Akande, Samuel O.; Abiodun, Babatunde J.; Gutowski, William J.

2018-02-01

In recent times, Ibadan has been experiencing an increase in mean temperature which appears to be linked to anthropogenic global warming. Previous studies have indicated that the warming may be accompanied by changes in extreme events. This study examined trends in mean and extreme temperatures over Ibadan during 1971-2012 at annual and seasonal scales using the high-resolution atmospheric reanalysis from European Centre for Medium-Range Weather Forecasts (ECMWF) twentieth-century dataset (ERA-20C) at 15 grid points. Magnitudes of linear trends in mean and extreme temperatures and their statistical significance were calculated using ordinary least squares and Mann-Kendall rank statistic tests. The results show that Ibadan has witnessed an increase in annual and seasonal mean minimum temperatures. The annual mean maximum temperature exhibited a non-significant decline in most parts of Ibadan. While trends in cold extremes at annual scale show warming, trends in coldest night show greater warming than in coldest day. At the seasonal scale, we found that Ibadan experienced a mix of positive and negative trends in absolute extreme temperature indices. However, cold extremes show the largest trend magnitudes, with trends in coldest night showing the greatest warming. The results compare well with those obtained from a limited number of stations. This study should inform decision-makers and urban planners about the ongoing warming in Ibadan.

Ocean acidification alters temperature and salinity preferences in larval fish.

PubMed

Pistevos, Jennifer C A; Nagelkerken, Ivan; Rossi, Tullio; Connell, Sean D

2017-02-01

Ocean acidification alters the way in which animals perceive and respond to their world by affecting a variety of senses such as audition, olfaction, vision and pH sensing. Marine species rely on other senses as well, but we know little of how these might be affected by ocean acidification. We tested whether ocean acidification can alter the preference for physicochemical cues used for dispersal between ocean and estuarine environments. We experimentally assessed the behavioural response of a larval fish (Lates calcarifer) to elevated temperature and reduced salinity, including estuarine water of multiple cues for detecting settlement habitat. Larval fish raised under elevated CO 2 concentrations were attracted by warmer water, but temperature had no effect on fish raised in contemporary CO 2 concentrations. In contrast, contemporary larvae were deterred by lower salinity water, where CO 2 -treated fish showed no such response. Natural estuarine water-of higher temperature, lower salinity, and containing estuarine olfactory cues-was only preferred by fish treated under forecasted high CO 2 conditions. We show for the first time that attraction by larval fish towards physicochemical cues can be altered by ocean acidification. Such alterations to perception and evaluation of environmental cues during the critical process of dispersal can potentially have implications for ensuing recruitment and population replenishment. Our study not only shows that freshwater species that spend part of their life cycle in the ocean might also be affected by ocean acidification, but that behavioural responses towards key physicochemical cues can also be negated through elevated CO 2 from human emissions.

A simple mathematical model to predict sea surface temperature over the northwest Indian Ocean

NASA Astrophysics Data System (ADS)

Noori, Roohollah; Abbasi, Mahmud Reza; Adamowski, Jan Franklin; Dehghani, Majid

2017-10-01

A novel and simple mathematical model was developed in this study to enhance the capacity of a reduced-order model based on eigenvectors (RMEV) to predict sea surface temperature (SST) in the northwest portion of the Indian Ocean, including the Persian and Oman Gulfs and Arabian Sea. Developed using only the first two of 12,416 possible modes, the enhanced RMEV closely matched observed daily optimum interpolation SST (DOISST) values. Spatial distribution of the first mode indicated the greatest variations in DOISST occurred in the Persian Gulf. Also, the slightly increasing trend in the temporal component of the first mode observed in the study area over the last 34 years properly reflected the impact of climate change and rising DOISST. Given its simplicity and high level of accuracy, the enhanced RMEV can be applied to forecast DOISST in oceans, which the poor forecasting performance and large computational-time of other numerical models may not allow.

Is the global mean temperature trend too low?

NASA Astrophysics Data System (ADS)

Venema, Victor; Lindau, Ralf

2015-04-01

The global mean temperature trend may be biased due to similar technological and economic developments worldwide. In this study we want to present a number of recent results that suggest that the global mean temperature trend might be steeper as generally thought. In the Global Historical Climate Network version 3 (GHCNv3) the global land surface temperature is estimated to have increased by about 0.8°C between 1880 and 2012. In the raw temperature record, the increase is 0.6°C; the 0.2°C difference is due to homogenization adjustments. Given that homogenization can only reduce biases, this 0.2°C stems from a partial correction of bias errors and it seems likely that the real non-climatic trend bias will be larger. Especially in regions with sparser networks, homogenization will not be able to improve the trend much. Thus if the trend bias in these regions is similar to the bias for more dense networks (industrialized countries), one would expect the real bias to be larger. Stations in sparse networks are representative for a larger region and are given more weight in the computation of the global mean temperature. If all stations are given equal weight, the homogenization adjustments of the GHCNv3 dataset are about 0.4°C per century. In the subdaily HadISH dataset one break with mean size 0.12°C is found every 15 years for the period 1973-2013. That would be a trend bias of 0.78°C per century on a station by station basis. Unfortunately, these estimates strongly focus on Western countries having more stations. It is known from the literature that rich countries have a (statistically insignificant) stronger trend in the global datasets. Regional datasets can be better homogenized than global ones, the main reason being that global datasets do not contain all stations known to the weather services. Furthermore, global datasets use automatic homogenization methods and have less or no metadata. Thus while regional data can be biased themselves, comparing them

Multi-model attribution of upper-ocean temperature changes using an isothermal approach.

PubMed

Weller, Evan; Min, Seung-Ki; Palmer, Matthew D; Lee, Donghyun; Yim, Bo Young; Yeh, Sang-Wook

2016-06-01

Both air-sea heat exchanges and changes in ocean advection have contributed to observed upper-ocean warming most evident in the late-twentieth century. However, it is predominantly via changes in air-sea heat fluxes that human-induced climate forcings, such as increasing greenhouse gases, and other natural factors such as volcanic aerosols, have influenced global ocean heat content. The present study builds on previous work using two different indicators of upper-ocean temperature changes for the detection of both anthropogenic and natural external climate forcings. Using simulations from phase 5 of the Coupled Model Intercomparison Project, we compare mean temperatures above a fixed isotherm with the more widely adopted approach of using a fixed depth. We present the first multi-model ensemble detection and attribution analysis using the fixed isotherm approach to robustly detect both anthropogenic and natural external influences on upper-ocean temperatures. Although contributions from multidecadal natural variability cannot be fully removed, both the large multi-model ensemble size and properties of the isotherm analysis reduce internal variability of the ocean, resulting in better observation-model comparison of temperature changes since the 1950s. We further show that the high temporal resolution afforded by the isotherm analysis is required to detect natural external influences such as volcanic cooling events in the upper-ocean because the radiative effect of volcanic forcings is short-lived.

Multi-model attribution of upper-ocean temperature changes using an isothermal approach

NASA Astrophysics Data System (ADS)

Weller, Evan; Min, Seung-Ki; Palmer, Matthew D.; Lee, Donghyun; Yim, Bo Young; Yeh, Sang-Wook

2016-06-01

Both air-sea heat exchanges and changes in ocean advection have contributed to observed upper-ocean warming most evident in the late-twentieth century. However, it is predominantly via changes in air-sea heat fluxes that human-induced climate forcings, such as increasing greenhouse gases, and other natural factors such as volcanic aerosols, have influenced global ocean heat content. The present study builds on previous work using two different indicators of upper-ocean temperature changes for the detection of both anthropogenic and natural external climate forcings. Using simulations from phase 5 of the Coupled Model Intercomparison Project, we compare mean temperatures above a fixed isotherm with the more widely adopted approach of using a fixed depth. We present the first multi-model ensemble detection and attribution analysis using the fixed isotherm approach to robustly detect both anthropogenic and natural external influences on upper-ocean temperatures. Although contributions from multidecadal natural variability cannot be fully removed, both the large multi-model ensemble size and properties of the isotherm analysis reduce internal variability of the ocean, resulting in better observation-model comparison of temperature changes since the 1950s. We further show that the high temporal resolution afforded by the isotherm analysis is required to detect natural external influences such as volcanic cooling events in the upper-ocean because the radiative effect of volcanic forcings is short-lived.

Estimation of river and stream temperature trends under haphazard sampling

USGS Publications Warehouse

Gray, Brian R.; Lyubchich, Vyacheslav; Gel, Yulia R.; Rogala, James T.; Robertson, Dale M.; Wei, Xiaoqiao

2015-01-01

Long-term temporal trends in water temperature in rivers and streams are typically estimated under the assumption of evenly-spaced space-time measurements. However, sampling times and dates associated with historical water temperature datasets and some sampling designs may be haphazard. As a result, trends in temperature may be confounded with trends in time or space of sampling which, in turn, may yield biased trend estimators and thus unreliable conclusions. We address this concern using multilevel (hierarchical) linear models, where time effects are allowed to vary randomly by day and date effects by year. We evaluate the proposed approach by Monte Carlo simulations with imbalance, sparse data and confounding by trend in time and date of sampling. Simulation results indicate unbiased trend estimators while results from a case study of temperature data from the Illinois River, USA conform to river thermal assumptions. We also propose a new nonparametric bootstrap inference on multilevel models that allows for a relatively flexible and distribution-free quantification of uncertainties. The proposed multilevel modeling approach may be elaborated to accommodate nonlinearities within days and years when sampling times or dates typically span temperature extremes.

Low-Temperature Alteration of the Seafloor: Impacts on Ocean Chemistry

NASA Astrophysics Data System (ADS)

Coogan, Laurence A.; Gillis, Kathryn M.

2018-05-01

Over 50% of Earth is covered by oceanic crust, the uppermost portion of which is a high-permeability layer of basaltic lavas through which seawater continuously circulates. Fluid flow is driven by heat lost from the oceanic lithosphere; the global fluid flux is dependent on plate creation rates and the thickness and distribution of overlying sediment, which acts as a low-permeability layer impeding seawater access to the crust. Fluid-rock reactions in the crust, and global chemical fluxes, depend on the average temperature in the aquifer, the fluid flux, and the composition of seawater. The average temperature in the aquifer depends largely on bottom water temperature and, to a lesser extent, on the average seafloor sediment thickness. Feedbacks between off-axis chemical fluxes and their controls may play an important role in modulating ocean chemistry and planetary climate on long timescales, but more work is needed to quantify these feedbacks.

Attribution of the 2015 record high sea surface temperatures over the central equatorial Pacific and tropical Indian Ocean

NASA Astrophysics Data System (ADS)

Park, In-Hong; Min, Seung-Ki; Yeh, Sang-Wook; Weller, Evan; Kim, Seon Tae

2017-04-01

This study assessed the anthropogenic contribution to the 2015 record-breaking high sea surface temperatures (SSTs) observed in the central equatorial Pacific and tropical Indian Ocean. Considering a close link between extreme warm events in these regions, we conducted a joint attribution analysis using a fraction of attributable risk approach. Probability of occurrence of such extreme anomalies and long-term trends for the two oceanic regions were compared between CMIP5 multi-model simulations with and without anthropogenic forcing. Results show that the excessive warming in both regions is well beyond the range of natural variability and robustly attributable to human activities due to greenhouse gas increase. We further explored associated mechanisms including the Bjerknes feedback and background anthropogenic warming. It is concluded that background warming was the main contribution to the 2015 extreme SST event over the central equatorial Pacific Ocean on a developing El Niño condition, which in turn induced the extreme SST event over the tropical Indian Ocean through the atmospheric bridge effect.

Heat Coma Temperature and Supercooling Point in Oceanic Sea Skaters (Heteroptera, Gerridae)

PubMed Central

Harada, Tetsuo

2018-01-01

Heat coma temperatures (HCTs) and super cooling points (SCPs) were examined for nearly 1000 oceanic sea skaters collected from in the Pacific and Indian Oceans representing four Halobates species; H. germanus, H. micans, H. sericeus, and H. sp. Analysis was conducted using the entire dataset because a negative correlation was seen between the HCTs and SCPs in all four species. A weak negative correlation was seen between HCTs and SCPs with a cross tolerance between warmer HCTs and colder SCPs. The weakness of the correlation may be due to the large size of the dataset and to the variability in ocean surface temperature. The negative correlation does however suggest that oceanic sea skaters may have some form of cross tolerance with a common physiological mechanism for their high and low temperature tolerances. PMID:29401693

Spatial and Temporal Temperature trends on Iraq during 1980-2015

NASA Astrophysics Data System (ADS)

Al-Timimi, Yassen K.; Al-Khudhairy, Aws A.

2018-05-01

Monthly Mean surface air temperature at 23 stations in Iraq were analyzed for temporal trends and spatial variation during 1980-2015. Seasonal and annual temperature was analyzed using Mann-Kendall test to detect the significant trend. The results of temporal analysis showed that during winter, spring, summer and Autumn have a positive trend in all the parts of Iraq. A tendency has also been observed towards warmer years, with significantly warmer summer and spring periods and slightly warmer autumn and winter, the highest increase is (3.5)°C in Basrah during the summer. The results of spatial analyze using the ArcGIS showed that the seasonal temperature can be divided into two or three distinct areas with high temperature in the south and decreasing towards north, where the trend of spatial temperature were decreasing from south to the north in all the four seasons.

Tropospheric temperature climatology and trends observed over the Middle East

NASA Astrophysics Data System (ADS)

Basha, Ghouse; Marpu, P. R.; Ouarda, T. B. M. J.

2015-10-01

In this study, we report for the first time, the upper air temperature climatology, and trends over the Middle East, which seem to be significantly affected by the changes associated with hot summer and low precipitation. Long term (1985-2012) radiosonde data from 12 stations are used to derive the mean temperature climatology and vertical trends. The study was performed by analyzing the data at different latitudes. The vertical profiles of air temperature show distinct behavior in terms of vertical and seasonal variability at different latitudes. The seasonal cycle of temperature at the 100 hPa, however, shows an opposite pattern compared to the 200 hPa levels. The temperature at 100 hPa shows a maximum during winter and minimum in summer. Spectral analysis shows that the annual cycle is dominant in comparison with the semiannual cycle. The time-series of temperature data was analyzed using the Bayesian change point analysis and cumulative sum method to investigate the changes in temperature trends. Temperature shows a clear change point during the year 1999 at all stations. Further, Modified Mann-Kendall test was applied to study the vertical trend, and analysis shows statistically significant lower tropospheric warming and cooling in upper troposphere after the year 1999. In general, the magnitude of the trend decreases with altitude in the troposphere. In all the latitude bands in lower troposphere, significant warming is observed, whereas at higher altitudes cooling is noticed based on 28 years temperature observations over the Middle East.

Maximum Drawdown of Atmospheric CO2 due to Biological Uptake in the Ocean and the Ocean Temperature Effect

NASA Astrophysics Data System (ADS)

Odalen, M.; Nycander, J.; Oliver, K. I. C.; Nilsson, J.; Brodeau, L.; Ridgwell, A.

2016-02-01

During glacials, atmospheric CO2 is significantly lowered; the decrease is about 1/3 or 90 ppm during the last four glacial cycles. Since the ocean reservoir of carbon, and hence the ocean capacity for storing carbon, is substantially larger than the atmospheric and terrestrial counterparts, it is likely that this lowering was caused by ocean processes, drawing the CO2 into the deep ocean. The Southern Ocean circulation and biological efficiency are widely accepted as having played an important part in this CO2 drawdown. However, the relative effects of different processes contributing to this oceanic uptake have not yet been well constrained. In this work, we focus on better constraining two of these processes; 1) the effect of increased efficiency of the biological carbon uptake, and 2) the effect of changes in global mean ocean temperature on the abiotic ocean-atmosphere CO2 equilibrium. By performing ensemble runs using an Earth System Model of Intermediate Complexity (EMIC) we examine the changes in atmospheric pCO2 achieved by 100% nutrient utilization efficiency of biology. The simulations display different ocean circulation patterns and hence different global ocean mean temperatures. By restoring the atmospheric pCO2 to a target value during the spin-up phase, the total carbon content differs between each of the ensemble members. The difference is due to circulation having direct effects on biology, but also on global ocean mean temperature, changing the solubility of CO2. This study reveals the relative importance of of the processes 1 and 2 (mentioned above) for atmospheric pCO2 in a changed climate. The results of this study also show that a difference in carbon content after spin-up can have a significant effect on the drawdown potential of a maximised biological efficiency. Thus, the choice of spin-up characteristics in a model study of climate change CO2 dynamics may significantly affect the outcome of the study.

Insights into ice-ocean interactions and fjord circulation from fjord sea surface temperatures at the Petermann Glacier, Greenland

NASA Astrophysics Data System (ADS)

Snow, T.; Shepherd, B.; Abdalati, W.; Scambos, T. A.

2016-12-01

Dynamic processes at marine-terminating outlet glaciers are responsible for over one-third of Greenland Ice Sheet (GIS) mass loss. Enhanced intrusion of warm ocean waters at the termini of these glaciers has contributed to elevated rates of ice thinning and terminus retreat over the last two decades. In situ oceanographic measurements and modeling studies show that basal melting of glaciers and subglacial discharge can cause buoyant plumes of water to rise to the fjord surface and influence fjord circulation characteristics. The temperature of these surface waters holds clues about ice-ocean interactions and small-scale circulation features along the glacier terminus that could contribute to outlet glacier mass loss, but the magnitude and duration of temperature variability remains uncertain. Satellite remote sensing has proven very effectiver for acquiring sea surface temperatuer (SST) data from these remote regions on a long-term, consistent basis and shows promise for identifying temperature anomalies at the ice front. However, these data sets have not been widely utilized to date. Here, we use satellite-derived sea surface temperatures to identify fjord surface outflow characteristics from 2000 to present at the Petermann Glacier, which drains 4% of the GIS and is experiencing 80% of its mass loss from basal melt. We find a general SST warming trend that coincides with early sea ice breakup and precedes two major calving events and ice speedup that began in 2010. Persistent SST anomalies along the terminus provide evidence of warm outflow that is consistent with buoyant plume model predictions. However, the anomalies are not evident early in the time series, suggesting that ocean inflow and ice-ocean interactions have experienced a regime shift since 2000. Our results provide valuable insight into fjord circulation patterns and the forcing mechanisms that contribute to terminus retreat. Comparing our results to ongoing modeling experiments, time series from

The temperature-ballast hypothesis explains carbon export efficiency observations in the Southern Ocean

NASA Astrophysics Data System (ADS)

Britten, Gregory L.; Wakamatsu, Lael; Primeau, François W.

2017-02-01

Carbon export from the Southern Ocean exerts a strong control on the ocean carbon sink, yet recent observations from the region demonstrate poorly understood relationships in which carbon export efficiency is weakly related to temperature. These observations conflict with traditional theory where export efficiency increases in colder waters. A recently proposed "temperature-ballast hypothesis" suggests an explanatory mechanism where the effect of temperature-dependent respiration is masked by variation in particle-ballast as upwelling waters move northward from Antarctica. We use observations and statistical models to test this mechanism and find positive support for the hypothesized temperature-ballast interactions. Best fitting models indicate a significant relation between export efficiency and silica-ballast while simultaneously revealing the expected inverse effect of temperature once ballast is accounted for. These findings reconcile model predictions, metabolic theory, and carbon export observations in the Southern Ocean and have consequences for how the ocean carbon sink responds to climate change.

Estimating trends in the global mean temperature record

NASA Astrophysics Data System (ADS)

Poppick, Andrew; Moyer, Elisabeth J.; Stein, Michael L.

2017-06-01

Given uncertainties in physical theory and numerical climate simulations, the historical temperature record is often used as a source of empirical information about climate change. Many historical trend analyses appear to de-emphasize physical and statistical assumptions: examples include regression models that treat time rather than radiative forcing as the relevant covariate, and time series methods that account for internal variability in nonparametric rather than parametric ways. However, given a limited data record and the presence of internal variability, estimating radiatively forced temperature trends in the historical record necessarily requires some assumptions. Ostensibly empirical methods can also involve an inherent conflict in assumptions: they require data records that are short enough for naive trend models to be applicable, but long enough for long-timescale internal variability to be accounted for. In the context of global mean temperatures, empirical methods that appear to de-emphasize assumptions can therefore produce misleading inferences, because the trend over the twentieth century is complex and the scale of temporal correlation is long relative to the length of the data record. We illustrate here how a simple but physically motivated trend model can provide better-fitting and more broadly applicable trend estimates and can allow for a wider array of questions to be addressed. In particular, the model allows one to distinguish, within a single statistical framework, between uncertainties in the shorter-term vs. longer-term response to radiative forcing, with implications not only on historical trends but also on uncertainties in future projections. We also investigate the consequence on inferred uncertainties of the choice of a statistical description of internal variability. While nonparametric methods may seem to avoid making explicit assumptions, we demonstrate how even misspecified parametric statistical methods, if attuned to the

Producing a Climate-Quality Database of Global Upper Ocean Profile Temperatures - The IQuOD (International Quality-controlled Ocean Database) Project.

NASA Astrophysics Data System (ADS)

Sprintall, J.; Cowley, R.; Palmer, M. D.; Domingues, C. M.; Suzuki, T.; Ishii, M.; Boyer, T.; Goni, G. J.; Gouretski, V. V.; Macdonald, A. M.; Thresher, A.; Good, S. A.; Diggs, S. C.

2016-02-01

Historical ocean temperature profile observations provide a critical element for a host of ocean and climate research activities. These include providing initial conditions for seasonal-to-decadal prediction systems, evaluating past variations in sea level and Earth's energy imbalance, ocean state estimation for studying variability and change, and climate model evaluation and development. The International Quality controlled Ocean Database (IQuOD) initiative represents a community effort to create the most globally complete temperature profile dataset, with (intelligent) metadata and assigned uncertainties. With an internationally coordinated effort organized by oceanographers, with data and ocean instrumentation expertise, and in close consultation with end users (e.g., climate modelers), the IQuOD initiative will assess and maximize the potential of an irreplaceable collection of ocean temperature observations (tens of millions of profiles collected at a cost of tens of billions of dollars, since 1772) to fulfil the demand for a climate-quality global database that can be used with greater confidence in a vast range of climate change related research and services of societal benefit. Progress towards version 1 of the IQuOD database, ongoing and future work will be presented. More information on IQuOD is available at www.iquod.org.

Pliocene three-dimensional global ocean temperature reconstruction

USGS Publications Warehouse

Dowsett, H.J.; Robinson, M.M.; Foley, K.M.

2009-01-01

A snapshot of the thermal structure of the mid-Piacenzian ocean is obtained by combining the Pliocene Research, Interpretation and Synoptic Mapping Project (PRISM3) multiproxy sea-surface temperature (SST) reconstruction with bottom water tempera-5 ture estimates produced using Mg/Ca paleothermometry. This reconstruction assumes a Pliocene water mass framework similar to that which exists today, with several important modifications. The area of formation of present day North Atlantic Deep Water (NADW) was expanded and extended further north toward the Arctic Ocean during the mid-Piacenzian relative to today. This, combined with a deeper Greenland-Scotland Ridge, allowed a greater volume of warmer NADW to enter the Atlantic Ocean. In the Southern Ocean, the Polar Front Zone was expanded relative to present day, but shifted closer to the Antarctic continent. This, combined with at least seasonal reduction in sea ice extent, resulted in decreased Antarctic BottomWater (AABW) production (relative to present day) as well as possible changes in the depth of intermediate wa15 ters. The reconstructed mid-Piacenzian three-dimensional ocean was warmer overall than today, and the hypothesized aerial extent of water masses appears to fit the limited stable isotopic data available for this time period. ?? Author(s) 2009.

On the Use of Ocean Dynamic Temperature for Hurricane Intensity Forecasting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balaguru, Karthik; Foltz, Gregory R.; Leung, L. Ruby

Sea surface temperature (SST) and the Tropical Cyclone Heat Potential (TCHP) are metrics used to incorporate the ocean's influence on hurricane intensification in the National Hurricane Center's Statistical Hurricane Intensity Prediction Scheme (SHIPS). While both SST and TCHP serve as useful measures of the upper-ocean heat content, they do not accurately represent ocean stratification effects. Here we show that replacing SST in the SHIPS framework with a dynamic temperature (Tdy), which accounts for the oceanic negative feedback to the hurricane's intensity arising from storm-induced vertical mixing and sea-surface cooling, improves the model performance. While the model with SST and TCHPmore » explains nearly 41% of the variance in 36-hr intensity changes, replacing SST with Tdy increases the variance explained to nearly 44%. Our results suggest that representation of the oceanic feedback, even through relatively simple formulations such as Tdy, may improve the performance of statistical hurricane intensity prediction models such as SHIPS.« less

Trends in record-breaking temperatures for the conterminous United States

NASA Astrophysics Data System (ADS)

Rowe, Clinton M.; Derry, Logan E.

2012-08-01

In an unchanging climate, record-breaking temperatures are expected to decrease in frequency over time, as established records become increasingly more difficult to surpass. This inherent trend in the number of record-breaking events confounds the interpretation of actual trends in the presence of any underlying climate change. Here, a simple technique to remove the inherent trend is introduced so that any remaining trend can be examined separately for evidence of a climate change. As this technique does not use the standard definition of a broken record, our records* are differentiated by an asterisk. Results for the period 1961-2010 indicate that the number of record* low daily minimum temperatures has been significantly and steadily decreasing nearly everywhere across the United States while the number of record* high daily minimum temperatures has been predominantly increasing. Trends in record* low and record* high daily maximum temperatures are generally weaker and more spatially mixed in sign. These results are consistent with other studies examining changes expected in a warming climate.

Observed Changes at the Surface of the Arctic Ocean

NASA Astrophysics Data System (ADS)

Ortmeyer, M.; Rigor, I.

2004-12-01

The Arctic has long been considered a harbinger of global climate change since simulations with global climate models predict that if the concentration of CO2 in the atmosphere doubles, the Arctic would warm by more than 5°C, compared to a warming of 2°C for subpolar regions (Manabe et al., 1991). And indeed, studies of the observational records show polar amplification of the warming trends (e.g. Serreze and Francis, 2004). These temperature trends are accompanied by myriad concurrent changes in Arctic climate. One of the first indicators of Arctic climate change was found by Walsh et al. (1996) using sea level pressure (SLP) data from the International Arctic Buoy Programme (IABP, http://iabp.apl.washington.edu). In this study, they showed that SLP over the Arctic Ocean decreased by over 4 hPa from 1979 - 1994. The decreases in SLP (winds) over the Arctic Ocean, forced changes in the circulation of sea ice and the surface ocean currents such that the Beaufort Gyre is reduced in size and speed (e.g. Rigor et al., 2002). Data from the IABP has also been assimilated into the global surface air temperature (SAT) climatologies (e.g. Jones et al. 1999), and the IABP SAT analysis shows that the temperature trends noted over land extend out over the Arctic Ocean. Specifically, Rigor et al. (2000) found warming trends in SAT over the Arctic Ocean during win¬ter and spring, with values as high as 2°C/decade in the eastern Arctic during spring. It should be noted that many of the changes in Arctic climate were first observed or explained using data from the IABP. The observations from IABP have been one of the cornerstones for environmental forecasting and studies of climate and climate change. These changes have a profound impact on wildlife and people. Many species and cultures depend on the sea ice for habitat and subsistence. Thus, monitoring the Arctic Ocean is crucial not only for our ability to detect climate change, but also to improve our understanding of the

Seasonal re-emergence of North Atlantic subsurface ocean temperature anomalies and Northern hemisphere climate

NASA Astrophysics Data System (ADS)

Sinha, Bablu; Blaker, Adam; Duchez, Aurelie; Grist, Jeremy; Hewitt, Helene; Hirschi, Joel; Hyder, Patrick; Josey, Simon; Maclachlan, Craig; New, Adrian

2017-04-01

A high-resolution coupled ocean atmosphere model is used to study the effects of seasonal re-emergence of North Atlantic subsurface ocean temperature anomalies on northern hemisphere winter climate. A 50-member control simulation is integrated from September 1 to 28 February and compared with a similar ensemble with perturbed ocean initial conditions. The perturbation consists of a density-compensated subsurface (deeper than 180m) temperature anomaly corresponding to the observed subsurface temperature anomaly for September 2010, which is known to have re-emerged at the ocean surface in subsequent months. The perturbation is confined to the North Atlantic Ocean between the Equator and 65 degrees North. The model has 1/4 degree horizontal resolution in the ocean and the experiment is repeated for two atmosphere horizontal resolutions ( 60km and 25km) in order to determine whether the sensitivity of the atmosphere to re-emerging temperature anomalies is dependent on resolution. The ensembles display a wide range of reemergence behaviour, in some cases re-emergence occurs by November, in others it is delayed or does not occur at all. A wide range of amplitudes of the re-emergent temperature anomalies is observed. In cases where re-emergence occurs, there is a marked effect on both the regional (North Atlantic and Europe) and hemispheric surface pressure and temperature patterns. The results highlight a potentially important process whereby ocean memory of conditions up to a year earlier can significantly enhance seasonal forecast skill.

Warm Middle Jurassic-Early Cretaceous high-latitude sea-surface temperatures from the Southern Ocean

NASA Astrophysics Data System (ADS)

Jenkyns, H. C.; Schouten-Huibers, L.; Schouten, S.; Sinninghe Damsté, J. S.

2012-02-01

Although a division of the Phanerozoic climatic modes of the Earth into "greenhouse" and "icehouse" phases is widely accepted, whether or not polar ice developed during the relatively warm Jurassic and Cretaceous Periods is still under debate. In particular, there is a range of isotopic and biotic evidence that favours the concept of discrete "cold snaps", marked particularly by migration of certain biota towards lower latitudes. Extension of the use of the palaeotemperature proxy TEX86 back to the Middle Jurassic indicates that relatively warm sea-surface conditions (26-30 °C) existed from this interval (∼160 Ma) to the Early Cretaceous (∼115 Ma) in the Southern Ocean, with a general warming trend through the Late Jurassic followed by a general cooling trend through the Early Cretaceous. The lowest sea-surface temperatures are recorded from around the Callovian-Oxfordian boundary, an interval identified in Europe as relatively cool, but do not fall below 25 °C. The early Aptian Oceanic Anoxic Event, identified on the basis of published biostratigraphy, total organic carbon and carbon-isotope stratigraphy, records an interval with the lowest, albeit fluctuating Early Cretaceous palaeotemperatures (∼26 °C), recalling similar phenomena recorded from Europe and the tropical Pacific Ocean. Extant belemnite δ18O data, assuming an isotopic composition of waters inhabited by these fossils of -1‰ SMOW, give palaeotemperatures throughout the Upper Jurassic-Lower Cretaceous interval that are consistently lower by ∼14 °C than does TEX86 and the molluscs likely record conditions below the thermocline. The long-term, warm climatic conditions indicated by the TEX86 data would only be compatible with the existence of continental ice if appreciable areas of high altitude existed on Antarctica, and/or in other polar regions, during the Mesozoic Era.

Investigating the Uncertainty in Global SST Trends Due to Internal Variations Using an Improved Trend Estimator

NASA Astrophysics Data System (ADS)

Lian, Tao; Shen, Zheqi; Ying, Jun; Tang, Youmin; Li, Junde; Ling, Zheng

2018-03-01

A new criterion was proposed recently to measure the influence of internal variations on secular trends in a time series. When the magnitude of the trend is greater than a theoretical threshold that scales the influence from internal variations, the sign of the estimated trend can be interpreted as the underlying long-term change. Otherwise, the sign may depend on the period chosen. An improved least squares method is developed here to further reduce the theoretical threshold and is applied to eight sea surface temperature (SST) data sets covering the period 1881-2013 to investigate whether there are robust trends in global SSTs. It is found that the warming trends in the western boundary regions, the South Atlantic, and the tropical and southern-most Indian Ocean are robust. However, robust trends are not found in the North Pacific, the North Atlantic, or the South Indian Ocean. The globally averaged SST and Indian Ocean Dipole indices are found to have robustly increased, whereas trends in the zonal SST gradient across the equatorial Pacific, Niño 3.4 SST, and the Atlantic Multidecadal Oscillation indices are within the uncertainty range associated with internal variations. These results indicate that great care is required when interpreting SST trends using the available records in certain regions and indices. It is worth noting that the theoretical threshold can be strongly influenced by low-frequency oscillations, and the above conclusions are based on the assumption that trends are linear. Caution should be exercised when applying the theoretical threshold criterion to real data.

Northwestern Pacific typhoon intensity controlled by changes in ocean temperatures.

PubMed

Mei, Wei; Xie, Shang-Ping; Primeau, François; McWilliams, James C; Pasquero, Claudia

2015-05-01

Dominant climatic factors controlling the lifetime peak intensity of typhoons are determined from six decades of Pacific typhoon data. We find that upper ocean temperatures in the low-latitude northwestern Pacific (LLNWP) and sea surface temperatures in the central equatorial Pacific control the seasonal average lifetime peak intensity by setting the rate and duration of typhoon intensification, respectively. An anomalously strong LLNWP upper ocean warming has favored increased intensification rates and led to unprecedentedly high average typhoon intensity during the recent global warming hiatus period, despite a reduction in intensification duration tied to the central equatorial Pacific surface cooling. Continued LLNWP upper ocean warming as predicted under a moderate [that is, Representative Concentration Pathway (RCP) 4.5] climate change scenario is expected to further increase the average typhoon intensity by an additional 14% by 2100.

Warm Ocean Temperatures Blanket the Far-Western Pacific

NASA Technical Reports Server (NTRS)

2001-01-01

These data, taken during a 10-day collection cycle ending March 9, 2001, show that above-normal sea-surface heights and warmer ocean temperatures(indicated by the red and white areas) still blanket the far-western tropical Pacific and much of the north (and south) mid-Pacific. Red areas are about 10centimeters (4 inches) above normal; white areas show the sea-surface height is between 14 and 32 centimeters (6 to 13 inches) above normal.

This build-up of heat dominating the Western Pacific was first noted by TOPEX/Poseidon oceanographers more than two years ago and has outlasted the El Nino and La Nina events of the past few years. See: http://www.jpl.nasa.gov/elnino/990127.html . This warmth contrasts with the Bering Sea, Gulf of Alaska and tropical Pacific where lower-than-normal sea levels and cool ocean temperatures continue (indicated by blue areas). The blue areas are between 5 and 13centimeters (2 and 5 inches) below normal, whereas the purple areas range from 14 to 18 centimeters (6 to 7 inches) below normal. Actually, the near-equatorial ocean cooled through the fall of 2000 and into mid-winter and continues almost La Nina-like.

Looking at the entire Pacific basin, the Pacific Decadal Oscillation's warm horseshoe and cool wedge pattern still dominates this sea-level height image. Most recent National Oceanic and Atmospheric Administration (NOAA) sea-surface temperature data also clearly illustrate the persistence of this basin-wide pattern. They are available at http://psbsgi1.nesdis.noaa.gov:8080/PSB/EPS/SST/climo.html

The U.S.-French TOPEX/Poseidon mission is managed by JPL for NASA's Earth Science Enterprise, Washington, D.C. JPL is a division of the California Institute of Technology in Pasadena. For more information on the TOPEX/Poseidon project, see: http://topex-www.jpl.nasa.gov

Influence of Aerosol Loading on Ocean Temperature Parameters Affecting the Evolution of Tropical Cyclone Formation Near Northern and Eastern Australia

NASA Astrophysics Data System (ADS)

Bhowmick, R.; Trepanier, J. C.

2017-12-01

Australia's northern and eastern coasts are highly affected by tropical cyclones (TC) occurring over the southeast Indian Ocean (SEIO) and southwest Pacific Ocean (SWPO) each year from October to May. TC prediction along the Australian coast is difficult because of the unpredictable nature of the TC tracks. TCs over this region are dependent on many climatological conditions, especially sea surface temperatures (SST) and upper ocean heat content (UOHC). TCs over the SWPO and SEIO are also sensitive to the El Niño Southern Oscillation, which causes seasonal, annual and decadal SST variations and variation in TC formation and strength. The SWPO and SEIO have experienced increasing temperatures in recent decades, and the trend may be related to a variety of atmospheric/oceanic changes, including changes to SST variability induced by changes in atmospheric aerosols. The aim of this paper is to study the influence of aerosol loading, defined by aerosol optical depth (AOD), on infrared SST (IRSST) anomalies, UOHC, and the number of days with named TCs (events with maximum sustained winds at least 17 m s-1) occurring over the SWPO and SEIO from 1985 - 2015.Granger causality is used to study the predictive capacity of ocean temperature variables and AOD for named TC days. Monthly satellite and meteorological data are examined to find spatial and temporal patterns of TC days with the different independent variables. Preliminary results show a positive relationship between AOD and TC days. Other sources of variability besides AOD over a longer time period are included here to provide a robust scenario of SWPO and SEIO's response to aerosol loading ultimately influencing TC formation. This study furthers the understanding of how TC incidence varies as a function of ocean temperature variability due to AOD variability in the SWPO and SEIO regions. This information is useful for the advancement of seasonal TC forecasting and hazard assessment and risk management strategies by

An ensemble of eddy-permitting global ocean reanalyses from the MyOcean project

NASA Astrophysics Data System (ADS)

Masina, Simona; Storto, Andrea; Ferry, Nicolas; Valdivieso, Maria; Haines, Keith; Balmaseda, Magdalena; Zuo, Hao; Drevillon, Marie; Parent, Laurent

2017-08-01

A set of four eddy-permitting global ocean reanalyses produced in the framework of the MyOcean project have been compared over the altimetry period 1993-2011. The main differences among the reanalyses used here come from the data assimilation scheme implemented to control the ocean state by inserting reprocessed observations of sea surface temperature (SST), in situ temperature and salinity profiles, sea level anomaly and sea-ice concentration. A first objective of this work includes assessing the interannual variability and trends for a series of parameters, usually considered in the community as essential ocean variables: SST, sea surface salinity, temperature and salinity averaged over meaningful layers of the water column, sea level, transports across pre-defined sections, and sea ice parameters. The eddy-permitting nature of the global reanalyses allows also to estimate eddy kinetic energy. The results show that in general there is a good consistency between the different reanalyses. An intercomparison against experiments without data assimilation was done during the MyOcean project and we conclude that data assimilation is crucial for correctly simulating some quantities such as regional trends of sea level as well as the eddy kinetic energy. A second objective is to show that the ensemble mean of reanalyses can be evaluated as one single system regarding its reliability in reproducing the climate signals, where both variability and uncertainties are assessed through the ensemble spread and signal-to-noise ratio. The main advantage of having access to several reanalyses differing in the way data assimilation is performed is that it becomes possible to assess part of the total uncertainty. Given the fact that we use very similar ocean models and atmospheric forcing, we can conclude that the spread of the ensemble of reanalyses is mainly representative of our ability to gauge uncertainty in the assimilation methods. This uncertainty changes a lot from one ocean

Are Karakoram temperatures out of phase compared to hemispheric trends?

NASA Astrophysics Data System (ADS)

Asad, Fayaz; Zhu, Haifeng; Zhang, Hui; Liang, Eryuan; Muhammad, Sher; Farhan, Suhaib Bin; Hussain, Iqtidar; Wazir, Muhammad Atif; Ahmed, Moinuddin; Esper, Jan

2017-05-01

In contrast to a global retreating trend, glaciers in the Karakoram showed stability and/or mass gaining during the past decades. This "Karakoram Anomaly" has been assumed to result from an out-of-phase temperature trend compared to hemispheric scales. However, the short instrumental observations from the Karakoram valley bottoms do not support a quantitative assessment of long-term temperature trends in this high mountain area. Here, we presented a new April-July temperature reconstruction from the Karakoram region in northern Pakistan based on a high elevation ( 3600 m a.s.l.) tree-ring chronology covering the past 438 years (AD 1575-2012). The reconstruction passes all statistical calibration and validation tests and represents 49 % of the temperature variance recorded over the 1955-2012 instrumental period. It shows a substantial warming accounting to about 1.12 °C since the mid-twentieth century, and 1.94 °C since the mid-nineteenth century, and agrees well with the Northern Hemisphere temperature reconstructions. These findings provide evidence that the Karakoram temperatures are in-phase, rather than out-of-phase, compared to hemispheric scales since the AD 1575. The synchronous temperature trends imply that the anomalous glacier behavior reported from the Karakoram may need further explanations beyond basic regional thermal anomaly.

Spatiotemporal evolution of the chlorophyll a trend in the North Atlantic Ocean.

PubMed

Zhang, Min; Zhang, Yuanling; Shu, Qi; Zhao, Chang; Wang, Gang; Wu, Zhaohua; Qiao, Fangli

2018-01-15

Analyses of the chlorophyll a concentration (chla) from satellite ocean color products have suggested the decadal-scale variability of chla linked to the climate change. The decadal-scale variability in chla is both spatially and temporally non-uniform. We need to understand the spatiotemporal evolution of chla in decadal or multi-decadal timescales to better evaluate its linkage to climate variability. Here, the spatiotemporal evolution of the chla trend in the North Atlantic Ocean for the period 1997-2016 is analyzed using the multidimensional ensemble empirical mode decomposition method. We find that this variable trend signal of chla shows a dipole pattern between the subpolar gyre and along the Gulf Stream path, and propagation along the opposite direction of the North Atlantic Current. This propagation signal has an overlapping variability of approximately twenty years. Our findings suggest that the spatiotemporal evolution of chla during the two most recent decades is part of the multidecadal variations and possibly regulated by the changes of Atlantic Meridional Overturning Circulation, whereas the mechanisms of such evolution patterns still need to be explored. Copyright © 2017 Elsevier B.V. All rights reserved.

Sea-ice transport driving Southern Ocean salinity and its recent trends.

PubMed

Haumann, F Alexander; Gruber, Nicolas; Münnich, Matthias; Frenger, Ivy; Kern, Stefan

2016-09-01

Recent salinity changes in the Southern Ocean are among the most prominent signals of climate change in the global ocean, yet their underlying causes have not been firmly established. Here we propose that trends in the northward transport of Antarctic sea ice are a major contributor to these changes. Using satellite observations supplemented by sea-ice reconstructions, we estimate that wind-driven northward freshwater transport by sea ice increased by 20 ± 10 per cent between 1982 and 2008. The strongest and most robust increase occurred in the Pacific sector, coinciding with the largest observed salinity changes. We estimate that the additional freshwater for the entire northern sea-ice edge entails a freshening rate of -0.02 ± 0.01 grams per kilogram per decade in the surface and intermediate waters of the open ocean, similar to the observed freshening. The enhanced rejection of salt near the coast of Antarctica associated with stronger sea-ice export counteracts the freshening of both continental shelf and newly formed bottom waters due to increases in glacial meltwater. Although the data sources underlying our results have substantial uncertainties, regional analyses and independent data from an atmospheric reanalysis support our conclusions. Our finding that northward sea-ice freshwater transport is also a key determinant of the mean salinity distribution in the Southern Ocean further underpins the importance of the sea-ice-induced freshwater flux. Through its influence on the density structure of the ocean, this process has critical consequences for the global climate by affecting the exchange of heat, carbon and nutrients between the deep ocean and surface waters.

Statistical analysis of stratospheric temperature and ozone profile data for trends and model comparison

NASA Technical Reports Server (NTRS)

Tiao, G. C.

1992-01-01

Work performed during the project period July 1, 1990 to June 30, 1992 on the statistical analysis of stratospheric temperature data, rawinsonde temperature data, and ozone profile data for the detection of trends is described. Our principal topics of research are trend analysis of NOAA stratospheric temperature data over the period 1978-1989; trend analysis of rawinsonde temperature data for the period 1964-1988; trend analysis of Umkehr ozone profile data for the period 1977-1991; and comparison of observed ozone and temperature trends in the lower stratosphere. Analysis of NOAA stratospheric temperature data indicates the existence of large negative trends at 0.4 mb level, with magnitudes increasing with latitudes away from the equator. Trend analysis of rawinsonde temperature data over 184 stations shows significant positive trends about 0.2 C per decade at surface to 500 mb range, decreasing to negative trends about -0.3 C at 100 to 50 mb range, and increasing slightly at 30 mb level. There is little evidence of seasonal variation in trends. Analysis of Umkehr ozone data for 12 northern hemispheric stations shows significant negative trends about -.5 percent per year in Umkehr layers 7-9 and layer 3, but somewhat less negative trends in layers 4-6. There is no pronounced seasonal variation in trends, especially in layers 4-9. A comparison was made of empirical temperature trends from rawinsonde data in the lower stratosphere with temperature changes determined from a one-dimensional radiative transfer calculation that prescribed a given ozone change over the altitude region, surface to 50 km, obtained from trend analysis of ozonsonde and Umkehr profile data. The empirical and calculated temperature trends are found in substantive agreement in profile shape and magnitude.

Ozone and temperature trends

NASA Technical Reports Server (NTRS)

Stolarski, Richard S.; Fioletov, Vitali; Bishop, Lane; Godin, Sophie; Bojkov, Rumen D.; Kirchhoff, Volker; Chanin, Marie-Lise; Zawodny, Joseph M.; Zerefos, Christos S.; Chu, William

1991-01-01

An update of the extensive reviews of the state of knowledge of measured ozone trends published in the Report of the International Ozone Trends Panel is presented. The update contains a review of progress since these reports, including reviewing of the ozone records, in most cases through March 1991. Also included are some new, unpublished reanalyses of these records including a complete reevaluation of 29 stations located in the former Soviet Union. The major new advance in knowledge of the measured ozone trend is the existence of independently calibrated satellite data records from the Total Ozone Mapping Spectrometer (TOMS) and Stratospheric Aerosol and Gas Experiment (SAG) instruments. These confirm many of the findings, originally derived from the Dobson record, concerning northern mid-latitude changes in ozone. We now have results from several instruments, whereas the previously reported changes were dependent on the calibration of a single instrument. This update will compare the ozone records from many different instruments to determine whether or not they provide a consistent picture of the ozone change that has occurred in the atmosphere. The update also briefly considers the problem of stratospheric temperature change. As in previous reports, this problem received significantly less attention, and the report is not nearly as complete. This area needs more attention in the future.

Effects of Precipitation on Ocean Mixed-Layer Temperature and Salinity as Simulated in a 2-D Coupled Ocean-Cloud Resolving Atmosphere Model

NASA Technical Reports Server (NTRS)

Li, Xiaofan; Sui, C.-H.; Lau, K-M.; Adamec, D.

1999-01-01

A two-dimensional coupled ocean-cloud resolving atmosphere model is used to investigate possible roles of convective scale ocean disturbances induced by atmospheric precipitation on ocean mixed-layer heat and salt budgets. The model couples a cloud resolving model with an embedded mixed layer-ocean circulation model. Five experiment are performed under imposed large-scale atmospheric forcing in terms of vertical velocity derived from the TOGA COARE observations during a selected seven-day period. The dominant variability of mixed-layer temperature and salinity are simulated by the coupled model with imposed large-scale forcing. The mixed-layer temperatures in the coupled experiments with 1-D and 2-D ocean models show similar variations when salinity effects are not included. When salinity effects are included, however, differences in the domain-mean mixed-layer salinity and temperature between coupled experiments with 1-D and 2-D ocean models could be as large as 0.3 PSU and 0.4 C respectively. Without fresh water effects, the nocturnal heat loss over ocean surface causes deep mixed layers and weak cooling rates so that the nocturnal mixed-layer temperatures tend to be horizontally-uniform. The fresh water flux, however, causes shallow mixed layers over convective areas while the nocturnal heat loss causes deep mixed layer over convection-free areas so that the mixed-layer temperatures have large horizontal fluctuations. Furthermore, fresh water flux exhibits larger spatial fluctuations than surface heat flux because heavy rainfall occurs over convective areas embedded in broad non-convective or clear areas, whereas diurnal signals over whole model areas yield high spatial correlation of surface heat flux. As a result, mixed-layer salinities contribute more to the density differences than do mixed-layer temperatures.

Global Surface Temperature Anomalies and Attribution

NASA Astrophysics Data System (ADS)

Pietrafesa, L. J.

2017-12-01

We study Non-Stationary, Non-Linear time series of global surface temperatures from 1850 to 2016, and via an empirical, mathematical methodology, we reveal the buried, internal modes of variability of planetary temperatures over the past 167 years, and find periods of cooling and warming, both in the ocean and the atmosphere over land, with multiple modes of variability; seasonal, annual, inter-annual, multi-year, decadal, multi-decadal, centennial and overall warming trends in the ocean, atmosphere and the combination therein. The oceanic rate of warming is less than two thirds of that of the atmosphere. While our findings on overall trends of fossil fuel burning and planetary temperatures are only visually correlative, by employing a mathematical methodology well known in ergonomics, this study causally links the upward rise in planetary surface temperature from the latter part of the 19th Century and into the 21st Century, to the contemporaneous upward rise in fossil fuel burning and suggests that if present fossil fuel burning is not curtailed there will be continued warming of the planet in the future.

Trends in the Zonal Winds over the Southern Ocean from the NCEP/NCAR Reanalysis and Scatterometers

NASA Astrophysics Data System (ADS)

Richman, J. G.

2002-12-01

The winds over the Southern Ocean for the entire 54-year (1948-2001) period of the NCEP/NCAR Reanalysis have been decomposed into Principal Components (Empirical Orthogonal Functions). The first EOF describes 83 percent of the variance in the zonal wind. The loading of the EOF shows the predominately westerly surface flow with strongest winds in the Indian sector of the Southern Ocean. The structure of this EOF is similar to the Southern Annular Mode (SAM) identified by Thompson, et al 2000. The amplitude of this EOF reveals a large trend of 4.42 cm/s/yr in the strength of the zonal wind corresponding to a nearly 50 percent increase in the wind stress over the Southern Ocean. Such a trend, if real, would be important in the dynamics of the Antarctic Circumpolar Current (ACC). Recent studies by Gille, et al. (2001), Olbers and Ivchenko (2001) and Gent et al. (2001) have shown that the transport of the ACC is correlated to the variability in the zonal wind with a monotonic increase in the transport with increasing zonal wind strength. However, errors in the data assimilation scheme for surface pressure observations on the Antarctic continent appears to have caused a spurious trend in the sea level pressure south of 40S of -0.2 hPa/yr (Hines, et al. 2000 and Marshall, 2002). The sea level pressure difference between 40S and 60S has risen by 8 hPa over the same period. This sea level pressure difference is used as a proxy for the strength of the zonal winds. Thus, the trend in the zonal wind EOF amplitude may be an artifact of model errors in the NCEP Reanalysis. To check this trend, we analyzed scatterometer winds over the Southern Ocean from the SEASAT, ERS (1 and 2), NSCAT and QuikScat satellites. The scatterometer data is not used in the NCEP Reanalysis and, thus, is an independent estimate of the winds. The SEASAT Scatterometer (SASS) operated for 90 days in July-September, 1978, while the ERS, NSCAT and QuikScat scatterometers provide a continuous dataset from

Sea surface temperature predictions using a multi-ocean analysis ensemble scheme

NASA Astrophysics Data System (ADS)

Zhang, Ying; Zhu, Jieshun; Li, Zhongxian; Chen, Haishan; Zeng, Gang

2017-08-01

This study examined the global sea surface temperature (SST) predictions by a so-called multiple-ocean analysis ensemble (MAE) initialization method which was applied in the National Centers for Environmental Prediction (NCEP) Climate Forecast System Version 2 (CFSv2). Different from most operational climate prediction practices which are initialized by a specific ocean analysis system, the MAE method is based on multiple ocean analyses. In the paper, the MAE method was first justified by analyzing the ocean temperature variability in four ocean analyses which all are/were applied for operational climate predictions either at the European Centre for Medium-range Weather Forecasts or at NCEP. It was found that these systems exhibit substantial uncertainties in estimating the ocean states, especially at the deep layers. Further, a set of MAE hindcasts was conducted based on the four ocean analyses with CFSv2, starting from each April during 1982-2007. The MAE hindcasts were verified against a subset of hindcasts from the NCEP CFS Reanalysis and Reforecast (CFSRR) Project. Comparisons suggested that MAE shows better SST predictions than CFSRR over most regions where ocean dynamics plays a vital role in SST evolutions, such as the El Niño and Atlantic Niño regions. Furthermore, significant improvements were also found in summer precipitation predictions over the equatorial eastern Pacific and Atlantic oceans, for which the local SST prediction improvements should be responsible. The prediction improvements by MAE imply a problem for most current climate predictions which are based on a specific ocean analysis system. That is, their predictions would drift towards states biased by errors inherent in their ocean initialization system, and thus have large prediction errors. In contrast, MAE arguably has an advantage by sampling such structural uncertainties, and could efficiently cancel these errors out in their predictions.

Seasonal to Interannual Surface Ocean Salinity Trends With Aquarius Data

NASA Astrophysics Data System (ADS)

Lagerloef, G. S. E.; Kao, H. Y.; Carey, D.

2017-12-01

An important scientific goal for satellite salinity observations is to document oceanic climate trends and their link to changes in the water cycle. This study is a re-examination of seasonal to interannual sea surface salinity (SSS) variations from more recent analyses of V5.0 reprocessing of the Aquarius satellite data, Sep 2011 to May 2015. Sensor calibration over these time scales has been a concern, and the V5.0 includes improved calibration reference data compared to previous versions, which will be explained. Orthogonal mode analyses show that the annual cycle dominates the variability, and is strongest in the tropics. Interannual trends indicate the principal salinity patterns during onset of the 2015-16 El Niño. Recognizing that the Aquarius data record is now finite (Sep 2011 through May 2015) due to the mission failure in early June 2015, we will conclude with a status summary of the disposition of the Aquarius data and the prospects for continuing satellite salinity measurements.

Marine heatwaves off eastern Tasmania: Trends, interannual variability, and predictability

NASA Astrophysics Data System (ADS)

Oliver, Eric C. J.; Lago, Véronique; Hobday, Alistair J.; Holbrook, Neil J.; Ling, Scott D.; Mundy, Craig N.

2018-02-01

Surface waters off eastern Tasmania are a global warming hotspot. Here, mean temperatures have been rising over several decades at nearly four times the global average rate, with concomitant changes in extreme temperatures - marine heatwaves. These changes have recently caused the marine biodiversity, fisheries and aquaculture industries off Tasmania's east coast to come under stress. In this study we quantify the long-term trends, variability and predictability of marine heatwaves off eastern Tasmania. We use a high-resolution ocean model for Tasmania's eastern continental shelf. The ocean state over the 1993-2015 period is hindcast, providing daily estimates of the three-dimensional temperature and circulation fields. Marine heatwaves are identified at the surface and subsurface from ocean temperature time series using a consistent definition. Trends in marine heatwave frequency are positive nearly everywhere and annual marine heatwave days and penetration depths indicate significant positive changes, particularly off southeastern Tasmania. A decomposition into modes of variability indicates that the East Australian Current is the dominant driver of marine heatwaves across the domain. Self-organising maps are used to identify 12 marine heatwave types, each with its own regionality, seasonality, and associated large-scale oceanic and atmospheric circulation patterns. The implications of this work for marine ecosystems and their management were revealed through review of past impacts and stakeholder discussions regarding use of these data.

Patterns and Variability in Global Ocean Chlorophyll: Satellite Observations and Modeling

NASA Technical Reports Server (NTRS)

Gregg, Watson

2004-01-01

Recent analyses of SeaWiFS data have shown that global ocean chlorophyll has increased more than 4% since 1998. The North Pacific ocean basin has increased nearly 19%. These trend analyses follow earlier results showing decadal declines in global ocean chlorophyll and primary production. To understand the causes of these changes and trends we have applied the newly developed NASA Ocean Biogeochemical Assimilation Model (OBAM), which is driven in mechanistic fashion by surface winds, sea surface temperature, atmospheric iron deposition, sea ice, and surface irradiance. The model utilizes chlorophyll from SeaWiFS in a daily assimilation. The model has in place many of the climatic variables that can be expected to produce the changes observed in SeaWiFS data. This enables us to diagnose the model performance, the assimilation performance, and possible causes for the increase in chlorophyll. A full discussion of the changes and trends, possible causes, modeling approaches, and data assimilation will be the focus of the seminar.

Ocean heat budget analysis on sea surface temperature anomaly in western Indian Ocean during strong-weak Asian summer monsoon

NASA Astrophysics Data System (ADS)

Fathrio, Ibnu; Manda, Atsuyoshi; Iizuka, Satoshi; Kodama, Yasu-Masa; Ishida, Sachinobu

2018-05-01

This study presents ocean heat budget analysis on seas surface temperature (SST) anomalies during strong-weak Asian summer monsoon (southwest monsoon). As discussed by previous studies, there was close relationship between variations of Asian summer monsoon and SST anomaly in western Indian Ocean. In this study we utilized ocean heat budget analysis to elucidate the dominant mechanism that is responsible for generating SST anomaly during weak-strong boreal summer monsoon. Our results showed ocean advection plays more important role to initate SST anomaly than the atmospheric prcess (surface heat flux). Scatterplot analysis showed that vertical advection initiated SST anomaly in western Arabian Sea and southwestern Indian Ocean, while zonal advection initiated SST anomaly in western equatorial Indian Ocean.

Spatiotemporal trends in mean temperatures and aridity index over Rwanda

NASA Astrophysics Data System (ADS)

Muhire, I.; Ahmed, F.

2016-01-01

This study aims at quantifying the trends in mean temperatures and aridity index over Rwanda for the period of 1961-1992, based on analysis of climatic data (temperatures, precipitations, and potential evapotranspiration). The analysis of magnitude and significance of trends in temperatures and aridity index show the degree of climate change and mark the level of vulnerability to extreme events (e.g., droughts) in different areas of the country. The study reveals that mean temperatures increased in most parts of the country, with a significant increase observed in the eastern lowlands and in the southwestern parts. The highlands located in the northwest and the Congo-Nile crest showed a nonsignificant increase in mean temperatures. Aridity index increased only in March, April, October, and November, corresponding with the rainy seasons. The remaining months of the year showed a decreasing trend. At an annual resolution, the highlands and the western region showed a rise in aridity index with a decreasing pattern over the eastern lowlands and the central plateau. Generally, the highlands presented a nonsignificant increase in mean temperatures and aridity index especially during the rainy seasons. The eastern lowlands showed a significant increase in mean temperatures and decreasing trends in aridity index. Therefore, these areas are bound to experience more droughts, leading to reduced water and consequent decline in agricultural production. On the other hand, the north highlands and southwest region will continue to be more productive.

World Ocean Database and the Global Temperature and Salinity Profile Program Database: Synthesis of historical and near real-time ocean profile data

NASA Astrophysics Data System (ADS)

Boyer, T.; Sun, L.; Locarnini, R. A.; Mishonov, A. V.; Hall, N.; Ouellet, M.

2016-02-01

The World Ocean Database (WOD) contains systematically quality controlled historical and recent ocean profile data (temperature, salinity, oxygen, nutrients, carbon cycle variables, biological variables) ranging from Captain Cooks second voyage (1773) to this year's Argo floats. The US National Centers for Environmental Information (NCEI) also hosts the Global Temperature and Salinity Profile Program (GTSPP) Continuously Managed Database (CMD) which provides quality controlled near-real time ocean profile data and higher level quality controlled temperature and salinity profiles from 1990 to present. Both databases are used extensively for ocean and climate studies. Synchronization of these two databases will allow easier access and use of comprehensive regional and global ocean profile data sets for ocean and climate studies. Synchronizing consists of two distinct phases: 1) a retrospective comparison of data in WOD and GTSPP to ensure that the most comprehensive and highest quality data set is available to researchers without the need to individually combine and contrast the two datasets and 2) web services to allow the constantly accruing near-real time data in the GTSPP CMD and the continuous addition and quality control of historical data in WOD to be made available to researchers together, seamlessly.

Alexander Polonsky Global warming hiatus, ocean variability and regional climate change

NASA Astrophysics Data System (ADS)

Polonsky, A.

2016-02-01

This presentation generalizes the results concerning ocean variability, large-scale interdecadal ocean-atmosphere interaction in the Atlantic and Pacific Oceans and their impact on global and regional climate change carried out by the author and his colleagues for about 20 years. It is demonstrated once more that Atlantic Multidecadal Oscillation (AMO, which was early referred by the author as "interdecadal mode of North Atlantic Oscillation") is the crucial natural interdecadal climatic signal for the Atlantic-European and Mediterranean regions. It is characterized by amplitude which is the same order as human-induced centennial climate change and exceeds trend-like anthropogenic change at the decadal scale. Fast increasing of the global and Northern Hemisphere air temperature in the last 30 yrs of XX century (especially pronounced in the North Atlantic region and surrounded areas) is due to coincidence of human-induced positive trend and transition from the negative to the positive phase of AMO. AMO accounts for about 50% (60%) of the global (Northern Hemisphere) temperature trend in that period. Recent global warming hiatus is mostly the result of switch off the AMO phase. Typical AMO temporal scale is dictated by meridional overturning variability in the Atlantic Ocean and associated magnitude of meridional heat transport. Pacific Decadal Oscillation (PDO) is the other natural interdecadal signal which significantly impacts the global and regional climate variability. The rate of the ocean warming for different periods assessed separately for the upper mixed layer and deeper layers using data of oceanic re-analysis since 1959 confirms the principal role of the natural interdecadal oceanic modes (AMO and PDO) in observing climate change. At the same time a lack of deep-ocean long-term observing system restricts the accuracy of assessment of the heat redistribution in the World Ocean. I thanks to Pavel Sukhonos for help in the presentation preparing.

Malaria resurgence in the East African highlands: Temperature trends revisited

PubMed Central

Pascual, M.; Ahumada, J. A.; Chaves, L. F.; Rodó, X.; Bouma, M.

2006-01-01

The incidence of malaria in the East African highlands has increased since the end of the 1970s. The role of climate change in the exacerbation of the disease has been controversial, and the specific influence of rising temperature (warming) has been highly debated following a previous study reporting no evidence to support a trend in temperature. We revisit this result using the same temperature data, now updated to the present from 1950 to 2002 for four high-altitude sites in East Africa where malaria has become a serious public health problem. With both nonparametric and parametric statistical analyses, we find evidence for a significant warming trend at all sites. To assess the biological significance of this trend, we drive a dynamical model for the population dynamics of the mosquito vector with the temperature time series and the corresponding detrended versions. This approach suggests that the observed temperature changes would be significantly amplified by the mosquito population dynamics with a difference in the biological response at least 1 order of magnitude larger than that in the environmental variable. Our results emphasize the importance of considering not just the statistical significance of climate trends but also their biological implications with dynamical models. PMID:16571662

Insolation-induced mid-Brunhes transition in Southern Ocean ventilation and deep-ocean temperature.

PubMed

Yin, Qiuzhen

2013-02-14

Glacial-interglacial cycles characterized by long cold periods interrupted by short periods of warmth are the dominant feature of Pleistocene climate, with the relative intensity and duration of past and future interglacials being of particular interest for civilization. The interglacials after 430,000 years ago were characterized by warmer climates and higher atmospheric concentrations of carbon dioxide than the interglacials before, but the cause of this climatic transition (the so-called mid-Brunhes event (MBE)) is unknown. Here I show, on the basis of model simulations, that in response to insolation changes only, feedbacks between sea ice, temperature, evaporation and salinity caused vigorous pre-MBE Antarctic bottom water formation and Southern Ocean ventilation. My results also show that strong westerlies increased the pre-MBE overturning in the Southern Ocean via an increased latitudinal insolation gradient created by changes in eccentricity during austral winter and by changes in obliquity during austral summer. The stronger bottom water formation led to a cooler deep ocean during the older interglacials. These insolation-induced differences in the deep-sea temperature and in the Southern Ocean ventilation between the more recent interglacials and the older ones were not expected, because there is no straightforward systematic difference in the astronomical parameters between the interglacials before and after 430,000 years ago. Rather than being a real 'event', the apparent MBE seems to have resulted from a series of individual interglacial responses--including notable exceptions to the general pattern--to various combinations of insolation conditions. Consequently, assuming no anthropogenic interference, future interglacials may have pre- or post-MBE characteristics without there being a systematic change in forcings. These findings are a first step towards understanding the magnitude change of the interglacial carbon dioxide concentration around 430

Spatiotemporal trends in extreme rainfall and temperature indices over Upper Tapi Basin, India

NASA Astrophysics Data System (ADS)

Sharma, Priyank J.; Loliyana, V. D.; S. R., Resmi; Timbadiya, P. V.; Patel, P. L.

2017-12-01

The flood risk across the globe is intensified due to global warming and subsequent increase in extreme temperature and precipitation. The long-term trends in extreme rainfall (1944-2013) and temperature (1969-2012) indices have been investigated at annual, seasonal, and monthly time scales using nonparametric Mann-Kendall (MK), modified Mann-Kendall (MMK), and Sen's slope estimator tests. The extreme rainfall and temperature indices, recommended by the Expert Team on Climate Change Detection Monitoring Indices (ETCCDMI), have been analyzed at finer spatial scales for trend detection. The results of trend analyses indicate decreasing trend in annual total rainfall, significant decreasing trend in rainy days, and increasing trend in rainfall intensity over the basin. The seasonal rainfall has been found to decrease for all the seasons except postmonsoon, which could affect the rain-fed agriculture in the basin. The 1- and 5-day annual maximum rainfalls exhibit mixed trends, wherein part of the basin experiences increasing trend, while other parts experience a decreasing trend. The increase in dry spells and concurrent decrease in wet spells are also observed over the basin. The extreme temperature indices revealed increasing trends in hottest and coldest days, while decreasing trends in coldest night are found over most parts of the basin. Further, the diurnal temperature range is also found to increase due to warming tendency in maximum temperature (T max) at a faster rate compared to the minimum temperature (T min). The increase in frequency and magnitude of extreme rainfall in the basin has been attributed to the increasing trend in maximum and minimum temperatures, reducing forest cover, rapid pace of urbanization, increase in human population, and thereby increase in the aerosol content in the atmosphere. The findings of the present study would significantly help in sustainable water resource planning, better decision-making for policy framework, and setting up

Drift in ocean currents impacts intergenerational microbial exposure to temperature

PubMed Central

Doblin, Martina A.; van Sebille, Erik

2016-01-01

Microbes are the foundation of marine ecosystems [Falkowski PG, Fenchel T, Delong EF (2008) Science 320(5879):1034–1039]. Until now, the analytical framework for understanding the implications of ocean warming on microbes has not considered thermal exposure during transport in dynamic seascapes, implying that our current view of change for these critical organisms may be inaccurate. Here we show that upper-ocean microbes experience along-trajectory temperature variability up to 10 °C greater than seasonal fluctuations estimated in a static frame, and that this variability depends strongly on location. These findings demonstrate that drift in ocean currents can increase the thermal exposure of microbes and suggests that microbial populations with broad thermal tolerance will survive transport to distant regions of the ocean and invade new habitats. Our findings also suggest that advection has the capacity to influence microbial community assemblies, such that regions with strong currents and large thermal fluctuations select for communities with greatest plasticity and evolvability, and communities with narrow thermal performance are found where ocean currents are weak or along-trajectory temperature variation is low. Given that fluctuating environments select for individual plasticity in microbial lineages, and that physiological plasticity of ancestors can predict the magnitude of evolutionary responses of subsequent generations to environmental change [Schaum CE, Collins S (2014) Proc Biol Soc 281(1793):20141486], our findings suggest that microbial populations in the sub-Antarctic (∼40°S), North Pacific, and North Atlantic will have the most capacity to adapt to contemporary ocean warming. PMID:27140608

Drift in ocean currents impacts intergenerational microbial exposure to temperature.

PubMed

Doblin, Martina A; van Sebille, Erik

2016-05-17

Microbes are the foundation of marine ecosystems [Falkowski PG, Fenchel T, Delong EF (2008) Science 320(5879):1034-1039]. Until now, the analytical framework for understanding the implications of ocean warming on microbes has not considered thermal exposure during transport in dynamic seascapes, implying that our current view of change for these critical organisms may be inaccurate. Here we show that upper-ocean microbes experience along-trajectory temperature variability up to 10 °C greater than seasonal fluctuations estimated in a static frame, and that this variability depends strongly on location. These findings demonstrate that drift in ocean currents can increase the thermal exposure of microbes and suggests that microbial populations with broad thermal tolerance will survive transport to distant regions of the ocean and invade new habitats. Our findings also suggest that advection has the capacity to influence microbial community assemblies, such that regions with strong currents and large thermal fluctuations select for communities with greatest plasticity and evolvability, and communities with narrow thermal performance are found where ocean currents are weak or along-trajectory temperature variation is low. Given that fluctuating environments select for individual plasticity in microbial lineages, and that physiological plasticity of ancestors can predict the magnitude of evolutionary responses of subsequent generations to environmental change [Schaum CE, Collins S (2014) Proc Biol Soc 281(1793):20141486], our findings suggest that microbial populations in the sub-Antarctic (∼40°S), North Pacific, and North Atlantic will have the most capacity to adapt to contemporary ocean warming.

Trends in Surface Temperature at High Latitudes

NASA Technical Reports Server (NTRS)

Comiso, Josefino C.

2012-01-01

The earliest signal of a climate change is expected to be found in the polar regions where warming is expected to be amplified on account of ice-albedo feedbacks associated with the high reflectivity of snow and ice. Because of general inaccessibility, there is a general paucity of in situ data and hence the need to use satellite data to observe the large-scale variability and trends in surface temperature in the region. Among the most important sensors for monitoring surface temperature has been the Advanced Very High Resolution Radiometer (AVHRR) which was first launched in 1978 and has provided continuous thermal infrared data since 1981. The top of the atmosphere data are converted to surface temperature data through various schemes that accounts for the unique atmospheric and surface conditions in the polar regions. Among the highest source of error in the data is cloud masking which is made more difficult in the polar region because of similar Signatures of clouds and snow lice covered areas. The availability of many more channels in the Moderate Resolution Imaging Spectroradiometer (MODIS) launched on board Terra satellite in December 1999 and on board Aqua in May 2002 (e.g., 36 visible and infrared channels compared to 5 for AVHRR) made it possible to minimize the error. Further capabilities were introduced with the Advanced Microwave Scanning Radiometer (AMSR) which has the appropriate frequency channels for the retrieval of sea surface temperature (SST). The results of analysis of the data show an amplified warming in the Arctic region, compared with global warming. The spatial distribution of warming is, however, not uniform and during the last 3 decades, positive temperature anomalies have been most pronounced in North America, Greenland and the Arctic basin. Some regions of the Arctic such as Siberia and the Bering Sea surprisingly show moderate cooling but this may be because these regions were anomalously warm in the 1980s when the satellite record

Arctic Ocean

NASA Technical Reports Server (NTRS)

Parkinson, Claire L.; Zukor, Dorothy J. (Technical Monitor)

2000-01-01

The Arctic Ocean is the smallest of the Earth's four major oceans, covering 14x10(exp 6) sq km located entirely within the Arctic Circle (66 deg 33 min N). It is a major player in the climate of the north polar region and has a variable sea ice cover that tends to increase its sensitivity to climate change. Its temperature, salinity, and ice cover have all undergone changes in the past several decades, although it is uncertain whether these predominantly reflect long-term trends, oscillations within the system, or natural variability. Major changes include a warming and expansion of the Atlantic layer, at depths of 200-900 m, a warming of the upper ocean in the Beaufort Sea, a considerable thinning (perhaps as high as 40%) of the sea ice cover, a lesser and uneven retreat of the ice cover (averaging approximately 3% per decade), and a mixed pattern of salinity increases and decreases.

Effect of Recent Sea Surface Temperature Trends on the Arctic Stratospheric Vortex

NASA Technical Reports Server (NTRS)

Garfinkel, Chaim I.; Oman, Luke; Hurwitz, Margaret

2015-01-01

The springtime Arctic polar vortex has cooled significantly over the satellite era, with consequences for ozone concentrations in the springtime transition season. The causes of this cooling trend are deduced by using comprehensive chemistry-climate model experiments. Approximately half of the satellite era early springtime cooling trend in the Arctic lower stratosphere was caused by changing sea surface temperatures (SSTs). An ensemble of experiments forced only by changing SSTs is compared to an ensemble of experiments in which both the observed SSTs and chemically- and radiatively-active trace species are changing. By comparing the two ensembles, it is shown that warming of Indian Ocean, North Pacific, and North Atlantic SSTs, and cooling of the tropical Pacific, have strongly contributed to recent polar stratospheric cooling in late winter and early spring, and to a weak polar stratospheric warming in early winter. When concentrations of ozone-depleting substances and greenhouse gases are fixed, polar ozone concentrations show a small but robust decline due to changing SSTs. Ozone changes are magnified in the presence of changing gas concentrations. The stratospheric changes can be understood by examining the tropospheric height and heat flux anomalies generated by the anomalous SSTs. Finally, recent SST changes have contributed to a decrease in the frequency of late winter stratospheric sudden warmings.

Mesospheric temperature trends derived from standard phase-height measurements

NASA Astrophysics Data System (ADS)

Peters, Dieter H. W.; Entzian, Günter; Keckhut, Philippe

2017-10-01

New homogeneous time series of daily standard phase-height (SPH) and daily plasma scale-height (PSH) have been derived from a 50-year long-radio-wave measurement of the broadcasting station Allouis (France, 162 kHz). The signal was received at Kühlungsborn (54°N, 12°E, Mecklenburg, Germany) and the present series is a third release. The daily time series of SPH shows in its spectrum dominant modes which are typical for the solar cycle (SC), for El Niño-Southern Oscillation (ENSO) and for quasi-biannual oscillation (QBO), indicating solar and lower atmospheric influences. Surprisingly, the time series of daily PSH shows a band of dominant cycles larger than 16 years. In order to exclude the influence of the winter anomaly in the determination of column-integrated mesospheric temperature trends the phase-height-temperature procedure is confined to summer months. The derived thickness temperature of the mesosphere decreased statistically significant over the period 1959-2008 after pre-whitening with summer mean of solar sun spot numbers. The trend value is in the order of about -1.05 K/decade if the stratopause trend is excluded. The linear regression is more pronounced, -1.35 K/decade for the period of 1963-1985 (2 SCs), but weaker, -0.51 K/decade during 1986-2008 (last 2 SCs). The linear regression is in very good agreement with a mean column-integrated mesospheric trend derived from OHP-Lidar temperatures on a monthly mean basis for the last two SCs. This clearly shows that the thickness temperature of the mesosphere derived from phase-height measurement is a useful proxy for the long-term summer temperature change in the mesosphere from 1959 until 2008.

Another round for noisy ocean temperature test

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, C.

1993-03-05

It's a deal a talk show host would kill for: $35 million to sound off for a while. But there's one other aspect of the bargain that might be a bit tough for the average radio personality: You've got to listen to your own noise and gauge whether the world is warming. Luckily, that's nothing new for oceanographer Walter Munk, who last week won funding from the Defense Advanced Research Projects Agency to conduct a second trial of his underwater sonic thermometer of the world's oceans. Sound waves are pulsed form underwater loudspeakers to receivers thousands of miles away. Bymore » the measuring the elapsed time, Munk and his collaborators can precisely measure temperatures in entire ocean basins and watch for signs of global warming.« less

West African warming: Investigating Temperature Trends and their relation between Precipitation Trends over West African Sahel.

NASA Astrophysics Data System (ADS)

LY, M., Jr.

2014-12-01

It is now admitted that the West African region faces a lot of constraints due to the comprehensiveness of the high climate variability and potential climate change. This is mainly due to the lack of a large number of datasets and long-term records as summarized in the in the IPCC reports. This paper aims to provide improved knowledge and evidence on current and future climate conditions, for better manage climate variability over seasons and from year to year and strengthen the capacity to adapt to future climate change. In this regards, we analyse the evolution of some extreme temperature and precipitation indices over a large area of West Africa. Prior results show a general warming trend at individual stations throughout the region during the period from 1960 to 2010, namely negative trends in the number of cool nights, and positive trends in the number of warm days and length of warm spells. Trends in rainfall-related indices are not as uniform as the ones in temperatures, rather they display marked multi-decadal variability, as expected. To refine analyses of temperature variations and their relation to precipitation we investigated on cluster analysis aimed at distinguishing different sub-regions, such as continental and coastal, and relevant seasons, such as wet, dry/cold and dry warm. This will contribute to significantly lower uncertainties by developing better and more tailored temperature and precipitation trends to inform the user communities on climate related risks, as well as enhance their resilience to food insecurity and other climate related disasters.

Warm mid-Cretaceous high-latitude sea-surface temperatures from the southern Tethys Ocean and cool high-latitude sea-surface temperatures from the Arctic Ocean: asymmetric worldwide distribution of dinoflagellates

NASA Astrophysics Data System (ADS)

Masure, Edwige; Desmares, Delphine; Vrielynck, Bruno

2014-05-01

Dealing with 87 articles and using a Geographical Information System, Masure and Vrielynck (2009) have mapped worldwide biogeography of 38 Late Albian dinoflagellate cysts and have demonstrated Cretaceous oceanic bioclimatic belts. For comparison 30 Aptian species derived from 49 studies (Masure et al., 2013) and 49 Cenomanian species recorded from 33 articles have been encountered. Tropical, Subtropical, Boreal, Austral, bipolar and cosmopolitan species have been identified and Cretaceous dinoflagellate biomes are introduced. Asymmetric distribution of Aptian and Late Albian/Cenomanian subtropical Tethyan species, from 40°N to 70°S, demonstrates asymmetric Aptian and Late Albian/Cenomanian Sea Surface Temperature (SST) gradients with warm water masses in high latitudes of Southern Ocean. The SST gradients were stronger in the Northern Hemisphere than in the Southern Hemisphere. We note that Aptian and Late Albian/Cenomanian dinoflagellates restricted to subtropical and subpolar latitudes met and mixed at 35-40°N, while they mixed from 30°S to 70°S and from 50°S to 70°S respectively in the Southern Hemisphere. Mixing belts extend on 5° in the Northern Hemisphere and along 40° (Aptian) and 20° (Late Albian/Cenomanian) in the Southern one. The board southern mixing belt of Tethyan and Austral dinoflagellates suggest co-occurrence of warm and cold currents. We record climatic changes such as the Early Aptian cooler period and Late Aptian and Albian warming through the poleward migration of species constrained to cool water masses. These species sensitive to temperature migrated from 35°N to 55°N through the shallow Greenland-Norwergian Seaway connecting the Central Atlantic and the Arctic Ocean. While Tethyan species did not migrate staying at 40°N. We suggest that the Greenland-Norwergian Seaway might has been a barrier until Late Albian/Cenomanian for oceanic Tethyan dinoflagellates stopped either by the shallow water column or temperature and salinity

Modelling impacts of temperature, and acidifying and eutrophying deposition on DOC trends

NASA Astrophysics Data System (ADS)

Sawicka, Kasia; Rowe, Ed; Evans, Chris; Monteith, Don; Vanguelova, Elena; Wade, Andrew; Clark, Joanna

2017-04-01

Surface water dissolved organic carbon (DOC) concentrations in large parts of the northern hemisphere have risen over the past three decades, raising concern about enhanced contributions of carbon to the atmosphere and seas and oceans. The effect of declining acid deposition has been identified as a key control on DOC trends in soil and surface waters, since pH and ionic strength affect sorption and desorption of DOC. However, since DOC is derived mainly from recently-fixed carbon, and organic matter decomposition rates are considered sensitive to temperature, uncertainty persists regarding the extent to the relative importance of different drivers that affect these upward trends. We ran the dynamic model MADOC (Model of Acidity and Soil Organic Carbon) for a range of UK soils (podzols, gleysols and peatland), for which the time-series were available, to consider the likely relative importance of decreased deposition of sulphate and chloride, accumulation of reactive N, and higher temperatures, on DOC production in different soils. Modelled patterns of DOC change generally agreed favourably with measurements collated over 10-20 years, but differed markedly between sites. While the acidifying effect of sulphur deposition appeared to be the predominant control on the observed soil water DOC trends in all the soils considered other than a blanket peat, the model suggested that over the long term, the effects of nitrogen deposition on N-limited soils may have been sufficient to elevate the DOC recovery trajectory significantly. The second most influential cause of rising DOC in the model simulations was N deposition in ecosystems that are N-limited and respond with stimulated plant growth. Although non-marine chloride deposition made some contribution to acidification and recovery, it was not amongst the main drivers of DOC change. Warming had almost no effect on modelled historic DOC trends, but may prove to be a significant driver of DOC in future via its influence

Recent trends of groundwater temperatures in Austria

NASA Astrophysics Data System (ADS)

Benz, Susanne A.; Bayer, Peter; Winkler, Gerfried; Blum, Philipp

2018-06-01

Climate change is one of if not the most pressing challenge modern society faces. Increasing temperatures are observed all over the planet and the impact of climate change on the hydrogeological cycle has long been shown. However, so far we have insufficient knowledge on the influence of atmospheric warming on shallow groundwater temperatures. While some studies analyse the implication climate change has for selected wells, large-scale studies are so far lacking. Here we focus on the combined impact of climate change in the atmosphere and local hydrogeological conditions on groundwater temperatures in 227 wells in Austria, which have in part been observed since 1964. A linear analysis finds a temperature change of +0.7 ± 0.8 K in the years from 1994 to 2013. In the same timeframe surface air temperatures in Austria increased by 0.5 ± 0.3 K, displaying a much smaller variety. However, most of the extreme changes in groundwater temperatures can be linked to local hydrogeological conditions. Correlation between groundwater temperatures and nearby surface air temperatures was additionally analysed. They vary greatly, with correlation coefficients of -0.3 in central Linz to 0.8 outside of Graz. In contrast, the correlation of nationwide groundwater temperatures and surface air temperatures is high, with a correlation coefficient of 0.83. All of these findings indicate that while atmospheric climate change can be observed in nationwide groundwater temperatures, individual wells are often primarily dominated by local hydrogeological conditions. In addition to the linear temperature trend, a step-wise model was also applied that identifies climate regime shifts, which were observed globally in the late 70s, 80s, and 90s. Hinting again at the influence of local conditions, at most 22 % of all wells show these climate regime shifts. However, we were able to identify an additional shift in 2007, which was observed by 37 % of all wells. Overall, the step-wise representation

1/f model for long-time memory of the ocean surface temperature

NASA Astrophysics Data System (ADS)

Fraedrich, Klaus; Luksch, Ute; Blender, Richard

2004-09-01

The 1/f spectrum of the ocean surface temperature in the Atlantic and Pacific midlatitudes is explained by a simple vertical diffusion model with a shallow mixed layer on top of a deep ocean. The model is forced at the air-sea interface with the total surface heat flux from a 1000 year climate simulation. The analysis reveals the role of ocean advection and substantiates estimates of internal thermal diffusivities.

Impacts of Ocean Acidification and Temperature Change on Zooxanthellae Density in Coral Stylophora pistillata

NASA Astrophysics Data System (ADS)

Pantaleo, G. E.; Martínez Fernández, A.; Paytan, A.

2016-12-01

As ocean conditions continue to change, marine ecosystems are significantly impacted. Many calcifying organisms are being affected by the gradual changes in ocean pH and temperature that continue to occur over time. Corals are organisms that engage in a symbiotic relationship with Symbiodinium dinoflagellates (zooxanthellae). Symbiodinium are responsible for photosynthetic activity within oligotrophic waters. Corals depend on high levels of aragonite saturation state of seawater in order to build their skeletal structure. Most corals have a relatively narrow optimal range of temperature and pH in which they thrive. However, it is thought that corals residing in the Gulf of Aqaba (Red Sea) are resilient to the effects of increasing temperature. Stylophora pistillata's response to environmental impacts was tested via a simulation of ocean conditions at a high temperature and high CO2 emission scenario (pH 7.65) and lower CO2 emission scenario (pH 7.85) that are predicted for the end of this century. We present the difference in zooxanthellae density following a short term experiment where corals were placed in seawater tanks at pH 7.65, 7.85 and 8.1 and temperature was increased by 4 degrees C above seawater temperature in order to measure the response of Stylophora pistillata to potential future ocean conditions.

Assessment of Plio-Pleistocene Sea Surface Temperature Evolution Across Ocean Basins, Hemispheres, and Latitudes

NASA Astrophysics Data System (ADS)

Peterson, L.; Lawrence, K. T.; Mauriello, H.; Wilson, J.; Holte, L.

2015-12-01

New sea surface temperature (SST) records from the southern Pacific and southern Atlantic Oceans allow assessment of similarities and differences in climate evolution across ocean basins, hemispheres, and latitudes over the last 5 million years. Our high-resolution, alkenone-derived SST records from ODP Sites 1088 (South Atlantic, 41°S) and 1125 (South Pacific, 42°S) share strong structural similarities. When compared with SST records from the mid-latitudes of the northern hemisphere, these records provide compelling evidence for broadly hemispherically symmetrical open-ocean temperature evolution in both ocean basins as tropical warm pools contracted over the Plio-Pleistocene. This symmetry in temperature evolution occurs despite strong asymmetries in the development of the cryosphere over this interval, which was marked by extensive northern hemisphere ice sheet growth. Parallel SST evolution across ocean basins and hemispheres suggests that on longterm (>105 yr) timescales, many regions of the world ocean are more sensitive to the global energy budget than to local or regional climate dynamics, although important exceptions include coastal upwelling zone SSTs, high latitude SSTs, and benthic δ18O. Our analysis further reveals that throughout the last 5 Ma, temperature evolution in the extra-tropical Pacific of both hemispheres is very similar to the evolution of SST in the eastern equatorial Pacific upwelling zone, revealing tight coupling between the growth of meridional and equatorial Pacific zonal temperature gradients over this interval as both the extra-tropics and the eastern equatorial Pacific cold tongue underwent cooling. Finally, while long term temperature evolution is broadly consistent across latitudes and ocean basins throughout the entire Plio-Pleistocene, we see evidence that climate coupling on orbital timescales strengthened significantly at 2.7 Ma, at which point obliquity-band coherence emerges among diverse SST records. We attribute this

Warming of the Global Ocean: Spatial Structure and Water-Mass Trends

NASA Technical Reports Server (NTRS)

Hakkinen, Sirpa; Rhines, Peter B.; Worthen, Denise L.

2016-01-01

This study investigates the multidecadal warming and interannual-to-decadal heat content changes in the upper ocean (0-700 m), focusing on vertical and horizontal patterns of variability. These results support a nearly monotonic warming over much of the World Ocean, with a shift toward Southern Hemisphere warming during the well-observed past decade. This is based on objectively analyzed gridded observational datasets and on a modeled state estimate. Besides the surface warming, a warming climate also has a subsurface effect manifesting as a strong deepening of the midthermocline isopycnals, which can be diagnosed directly from hydrographic data. This deepening appears to be a result of heat entering via subduction and spreading laterally from the high-latitude ventilation regions of subtropical mode waters. The basin-average multidecadal warming mainly expands the subtropical mode water volume, with weak changes in the temperature-salinity (u-S) relationship (known as ''spice'' variability). However, the spice contribution to the heat content can be locally large, for example in Southern Hemisphere. Multidecadal isopycnal sinking has been strongest over the southern basins and weaker elsewhere with the exception of the Gulf Stream/North Atlantic Current/subtropical recirculation gyre. At interannual to decadal time scales, wind-driven sinking and shoaling of density surfaces still dominate ocean heat content changes, while the contribution from temperature changes along density surfaces tends to decrease as time scales shorten.

Changes in size and trends of North American sea duck populations associated with North Pacific oceanic regime shifts

USGS Publications Warehouse

Flint, Paul L.

2013-01-01

Broad-scale multi-species declines in populations of North American sea ducks for unknown reasons is cause for management concern. Oceanic regime shifts have been associated with rapid changes in ecosystem structure of the North Pacific and Bering Sea. However, relatively little is known about potential effects of these changes in oceanic conditions on marine bird populations at broad scales. I examined changes in North American breeding populations of sea ducks from 1957 to 2011 in relation to potential oceanic regime shifts in the North Pacific in 1977, 1989, and 1998. There was strong support for population-level effects of regime shifts in 1977 and 1989, but little support for an effect of the 1998 shift. The continental-level effects of these regime shifts differed across species groups and time. Based on patterns of sea duck population dynamics associated with regime shifts, it is unclear if the mechanism of change relates to survival or reproduction. Results of this analysis support the hypothesis that population size and trends of North American sea ducks are strongly influenced by oceanic conditions. The perceived population declines appear to have halted >20 years ago, and populations have been relatively stable or increasing since that time. Given these results, we should reasonably expect dramatic changes in sea duck population status and trends with future oceanic regime shifts.

Urban and peri-urban precipitation and air temperature trends in mega cities of the world using multiple trend analysis methods

NASA Astrophysics Data System (ADS)

Ajaaj, Aws A.; Mishra, Ashok K.; Khan, Abdul A.

2018-04-01

Urbanization plays an important role in altering local to regional climate. In this study, the trends in precipitation and the air temperature were investigated for urban and peri-urban areas of 18 mega cities selected from six continents (representing a wide range of climatic patterns). Multiple statistical tests were used to examine long-term trends in annual and seasonal precipitation and air temperature for the selected cities. The urban and peri-urban areas were classified based on the percentage of land imperviousness. Through this study, it was evident that removal of the lag-k serial correlation caused a reduction of approximately 20 to 30% in significant trend observability for temperature and precipitation data. This observation suggests that appropriate trend analysis methodology for climate studies is necessary. Additionally, about 70% of the urban areas showed higher positive air temperature trends, compared with peri-urban areas. There were not clear trend signatures (i.e., mix of increase or decrease) when comparing urban vs peri-urban precipitation in each selected city. Overall, cities located in dry areas, for example, in Africa, southern parts of North America, and Eastern Asia, showed a decrease in annual and seasonal precipitation, while wetter conditions were favorable for cities located in wet regions such as, southeastern South America, eastern North America, and northern Europe. A positive relationship was observed between decadal trends of annual/seasonal air temperature and precipitation for all urban and peri-urban areas, with a higher rate being observed for urban areas.

Global and Regional Trends of Aerosol Optical Depth over Land and Ocean Using SeaWiFS Measurements from 1997 to 2010

NASA Technical Reports Server (NTRS)

Hsu, N. C.; Gautam, R.; Sayer, A. M.; Bettenhausen, C.; Li, C.; Jeong, M. J.; Tsay, S. C.; Holben, B. N.

2012-01-01

Both sensor calibration and satellite retrieval algorithm play an important role in the ability to determine accurately long-term trends from satellite data. Owing to the unprecedented accuracy and long-term stability of its radiometric calibration, the SeaWiFS measurements exhibit minimal uncertainty with respect to sensor calibration. In this study, we take advantage of this well-calibrated set of measurements by applying a newly-developed aerosol optical depth (AOD) retrieval algorithm over land and ocean to investigate the distribution of AOD, and to identify emerging patterns and trends in global and regional aerosol loading during its 13-year mission. Our results indicate that the averaged AOD trend over global ocean is weakly positive from 1998 to 2010 and comparable to that observed by MODIS but opposite in sign to that observed by AVHRR during overlapping years. On a smaller scale, different trends are found for different regions. For example, large upward trends are found over the Arabian Peninsula that indicate a strengthening of the seasonal cycle of dust emission and transport processes over the whole region as well as over downwind oceanic regions. In contrast, a negative-neutral tendency is observed over the desert/arid Saharan region as well as in the associated dust outflow over the north Atlantic. Additionally, we found decreasing trends over the eastern US and Europe, and increasing trends over countries such as China and India that are experiencing rapid economic development. In general, these results are consistent with those derived from ground-based AERONET measurements.

Nonuniform ocean acidification and attenuation of the ocean carbon sink

NASA Astrophysics Data System (ADS)

Fassbender, Andrea J.; Sabine, Christopher L.; Palevsky, Hilary I.

2017-08-01

Surface ocean carbon chemistry is changing rapidly. Partial pressures of carbon dioxide gas (pCO2) are rising, pH levels are declining, and the ocean's buffer capacity is eroding. Regional differences in short-term pH trends primarily have been attributed to physical and biological processes; however, heterogeneous seawater carbonate chemistry may also be playing an important role. Here we use Surface Ocean CO2 Atlas Version 4 data to develop 12 month gridded climatologies of carbonate system variables and explore the coherent spatial patterns of ocean acidification and attenuation in the ocean carbon sink caused by rising atmospheric pCO2. High-latitude regions exhibit the highest pH and buffer capacity sensitivities to pCO2 increases, while the equatorial Pacific is uniquely insensitive due to a newly defined aqueous CO2 concentration effect. Importantly, dissimilar regional pH trends do not necessarily equate to dissimilar acidity ([H+]) trends, indicating that [H+] is a more useful metric of acidification.

Temperature Trends in the White Mountains of New Hampshire

NASA Astrophysics Data System (ADS)

Murray, G.; Kelsey, E. P.; Raudzens Bailey, A.

2014-12-01

Located at the summit of Mount Washington (1917 m asl; ~800 hPa), the highest peak in the northeastern United States, the Mount Washington Observatory has meticulously recorded hourly temperature, humidity, cloud-cover, and other atmospheric variables for over 80 years using the same standard procedures to ensure high-quality, homogeneous data. Nearby Hubbard Brook Experimental Forest (253 m asl; ~980 hPa), a Long-Term Ecological Research site, has recorded atmospheric and environmental data since 1956. Together, these two sites provide a unique opportunity to evaluate elevation-dependent climate changes. Using Sen's slope and the Mann Kendall non-parameteric test we examine annual and seasonal trends in minimum, maximum, and mean temperatures. Both Mount Washington and Hubbard Brook exhibit 56-yr warming trends for most seasons, however, the magnitudes and statistical significances are variable, suggesting the processes controlling these trends likely differ with elevation. Since 1957, for instance, spring maximum temperatures at Hubbard Brook have warmed 0.32 °C dec-1 and winter minimums have increased 0.54 °C dec-1, both well within the range reported for six neighboring low elevation stations from 1970-2012 (Wake et al, 2014a,b). In comparison, Mount Washington summit seasonal minimum temperature trends are typically weaker, with changes in winter minimums (the largest of the seasons) reaching only 0.33 °C dec-1. In this presentation, we highlight differences between these two long-term records and discuss possible role of moist processes and boundary layer/free troposphere exposure in causing their divergence. Authors are planning to study the effects of humidity and cloud-cover on summit temperatures and to investigate how changes in the frequency with which the summit is exposed to boundary layer and free tropospheric air masses influences these relationships.

Mesopause region temperature variability and its trend in southern Brazil

NASA Astrophysics Data System (ADS)

Venturini, Mateus S.; Bageston, José V.; Caetano, Nattan R.; Peres, Lucas V.; Bencherif, Hassan; Schuch, Nelson J.

2018-03-01

Nowadays, the study of the upper atmosphere is increasing, mostly because of the need to understand the patterns of Earth's atmosphere. Since studies on global warming have become very important for the development of new technologies, understanding all regions of the atmosphere becomes an unavoidable task. In this paper, we aim to analyze the temperature variability and its trend in the mesosphere and lower thermosphere (MLT) region during a period of 12 years (from 2003 to 2014). For this purpose, three different heights, i.e., 85, 90 and 95 km, were focused on in order to investigate the upper atmosphere, and a geographic region different to other studies was chosen, in the southern region of Brazil, centered in the city of Santa Maria, RS (29°41'02'' S; 53°48'25'' W). In order to reach the objectives of this work, temperature data from the SABER instrument (Sounding of the Atmosphere using Broadband Emission Radiometry), aboard NASA's Thermosphere Ionosphere Mesosphere Energetics Dynamics (TIMED) satellite, were used. Finally, two cases were studied related to distinct grids of latitude/longitude used to obtain the mean temperature profiles. The first case considered a grid of 20° × 20° lat/long, centered in Santa Maria, RS, Brazil. In the second case, the region was reduced to a size of 15° × 15° in order to compare the results and discuss the two cases in terms of differences or similarities in temperature trends. Observations show that the size of the geographical area used for the average temperature profiles can influence the results of variability and trend of the temperature. In addition, reducing the time duration of analyses from 24 to 12 h a day also influences the trend significantly. For the smaller geographical region (15° × 15°) and the 12 h daily time window (09:00-21:00 UT) it was found that the main contributions for the temperature variability at the three heights were the annual and semi-annual cycles and the solar flux influence

Working Towards Deep-Ocean Temperature Monitoring by Studying the Acoustic Ambient Noise Field in the South Pacific Ocean

NASA Astrophysics Data System (ADS)

Sambell, K.; Evers, L. G.; Snellen, M.

2017-12-01

Deriving the deep-ocean temperature is a challenge. In-situ observations and satellite observations are hardly applicable. However, knowledge about changes in the deep ocean temperature is important in relation to climate change. Oceans are filled with low-frequency sound waves created by sources such as underwater volcanoes, earthquakes and seismic surveys. The propagation of these sound waves is temperature dependent and therefore carries valuable information that can be used for temperature monitoring. This phenomenon is investigated by applying interferometry to hydroacoustic data measured in the South Pacific Ocean. The data is measured at hydrophone station H03 which is part of the International Monitoring System (IMS). This network consists of several stations around the world and is in place for the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The station consists of two arrays located north and south of Robinson Crusoe Island separated by 50 km. Both arrays consist of three hydrophones with an intersensor distance of 2 km located at a depth of 1200 m. This depth is in range of the SOFAR channel. Hydroacoustic data measured at the south station is cross-correlated for the time period 2014-2017. The results are improved by applying one-bit normalization as a preprocessing step. Furthermore, beamforming is applied to the hydroacoustic data in order to characterize ambient noise sources around the array. This shows the presence of a continuous source at a backazimuth between 180 and 200 degrees throughout the whole time period, which is in agreement with the results obtained by cross-correlation. Studies on source strength show a seasonal dependence. This is an indication that the sound is related to acoustic activity in Antarctica. Results on this are supported by acoustic propagation modeling. The normal mode technique is used to study the sound propagation from possible source locations towards station H03.

Ocean acidification and temperature increase impact mussel shell shape and thickness: problematic for protection?

PubMed

Fitzer, Susan C; Vittert, Liberty; Bowman, Adrian; Kamenos, Nicholas A; Phoenix, Vernon R; Cusack, Maggie

2015-11-01

Ocean acidification threatens organisms that produce calcium carbonate shells by potentially generating an under-saturated carbonate environment. Resultant reduced calcification and growth, and subsequent dissolution of exoskeletons, would raise concerns over the ability of the shell to provide protection for the marine organism under ocean acidification and increased temperatures. We examined the impact of combined ocean acidification and temperature increase on shell formation of the economically important edible mussel Mytilus edulis. Shell growth and thickness along with a shell thickness index and shape analysis were determined. The ability of M. edulis to produce a functional protective shell after 9 months of experimental culture under ocean acidification and increasing temperatures (380, 550, 750, 1000 μatm pCO 2, and 750, 1000 μatm pCO 2 + 2°C) was assessed. Mussel shells grown under ocean acidification conditions displayed significant reductions in shell aragonite thickness, shell thickness index, and changes to shell shape (750, 1000 μatm pCO 2) compared to those shells grown under ambient conditions (380 μatm pCO 2). Ocean acidification resulted in rounder, flatter mussel shells with thinner aragonite layers likely to be more vulnerable to fracture under changing environments and predation. The changes in shape presented here could present a compensatory mechanism to enhance protection against predators and changing environments under ocean acidification when mussels are unable to grow thicker shells. Here, we present the first assessment of mussel shell shape to determine implications for functional protection under ocean acidification.

Global patterns of predator diversity in the open oceans.

PubMed

Worm, Boris; Sandow, Marcel; Oschlies, Andreas; Lotze, Heike K; Myers, Ransom A

2005-08-26

The open oceans comprise most of the biosphere, yet patterns and trends of species diversity there are enigmatic. Here, we derive worldwide patterns of tuna and billfish diversity over the past 50 years, revealing distinct subtropical "hotspots" that appeared to hold generally for other predators and zooplankton. Diversity was positively correlated with thermal fronts and dissolved oxygen and a nonlinear function of temperature (approximately 25 degrees C optimum). Diversity declined between 10 and 50% in all oceans, a trend that coincided with increased fishing pressure, superimposed on strong El Niño-Southern Oscillation-driven variability across the Pacific. We conclude that predator diversity shows a predictable yet eroding pattern signaling ecosystem-wide changes linked to climate and fishing.

The Effects of Global Warming on Temperature and Precipitation Trends in Northeast America

NASA Astrophysics Data System (ADS)

Francis, F.

2013-12-01

The objective of this paper is to discuss the analysis of results in temperature and precipitation (rainfall) data and how they are affected by the theory of global warming in Northeast America. The topic was chosen because it will show the trends in temperature and precipitation and their relations to global warming. Data was collected from The Global Historical Climatology Network (GHCN). The data range from years of 1973 to 2012. We were able to calculate the yearly and monthly regress to estimate the relationship of variables found in the individual sources. With the use of specially designed software, analysis and manual calculations we are able to give a visualization of these trends in precipitation and temperature and to question if these trends are due to the theory of global warming. With the Calculation of the trends in slope we were able to interpret the changes in minimum and maximum temperature and precipitation. Precipitation had a 9.5 % increase over the past forty years, while maximum temperature increased 1.9 %, a greater increase is seen in minimum temperature of 3.3 % was calculated over the years. The trends in precipitation, maximum and minimum temperature is statistically significant at a 95% level.

Mitigating Climate Change with Ocean Pipes: Influencing Land Temperature and Hydrology and Termination Overshoot Risk

NASA Astrophysics Data System (ADS)

Kwiatkowski, L.; Caldeira, K.; Ricke, K.

2014-12-01

With increasing risk of dangerous climate change geoengineering solutions to Earth's climate problems have attracted much attention. One proposed geoengineering approach considers the use of ocean pipes as a means to increase ocean carbon uptake and the storage of thermal energy in the deep ocean. We use a latest generation Earth System Model (ESM) to perform simulations of idealised extreme implementations of ocean pipes. In our simulations, downward transport of thermal energy by ocean pipes strongly cools the near surface atmosphere - by up to 11°C on a global mean. The ocean pipes cause net thermal energy to be transported from the terrestrial environment to the deep ocean while increasing the global net transport of water to land. By cooling the ocean surface more than the land, ocean pipes tend to promote a monsoonal-type circulation, resulting in increased water vapour transport to land. Throughout their implementation, ocean pipes prevent energy from escaping to space, increasing the amount of energy stored in Earth's climate system despite reductions in surface temperature. As a consequence, our results indicate that an abrupt termination of ocean pipes could cause dramatic increases in surface temperatures beyond that which would have been obtained had ocean pipes not been implemented.

Shift in tuna catches due to ocean warming.

PubMed

Monllor-Hurtado, Alberto; Pennino, Maria Grazia; Sanchez-Lizaso, José Luis

2017-01-01

Ocean warming is already affecting global fisheries with an increasing dominance of catches of warmer water species at higher latitudes and lower catches of tropical and subtropical species in the tropics. Tuna distributions are highly conditioned by sea temperature, for this reason and their worldwide distribution, their populations may be a good indicator of the effect of climate change on global fisheries. This study shows the shift of tuna catches in subtropical latitudes on a global scale. From 1965 to 2011, the percentage of tropical tuna in longliner catches exhibited a significantly increasing trend in a study area that included subtropical regions of the Atlantic and western Pacific Oceans and partially the Indian Ocean. This may indicate a movement of tropical tuna populations toward the poles in response to ocean warming. Such an increase in the proportion of tropical tuna in the catches does not seem to be due to a shift of the target species, since the trends in Atlantic and Indian Oceans of tropical tuna catches are decreasing. Our results indicate that as populations shift towards higher latitudes the catches of these tropical species did not increase. Thus, at least in the Atlantic and Indian Oceans, tropical tuna catches have reduced in tropical areas.

Temperature and heat wave trends in northwest Mexico

NASA Astrophysics Data System (ADS)

Martínez-Austria, Polioptro F.; Bandala, Erick R.; Patiño-Gómez, Carlos

2016-02-01

Increase in temperature extremes is one of the main expected impacts of climate change, as well as one of the first signs of its occurrence. Nevertheless, results emerging from General Circulation Models, while sufficient for large scales, are not enough for forecasting local trends and, hence, the IPCC has called for local studies based on on-site data. Indeed, it is expected that climate extremes will be detected much earlier than changes in climate averages. Heat waves are among the most important and least studied climate extremes, however its occurrence has been only barely studied and even its very definition remains controversial. This paper discusses the observed changes in temperature trends and heat waves in Northwestern Mexico, one of the most vulnerable regions of the country. The climate records in two locations of the region are analyzed, including one of the cities with extreme climate in Mexico, Mexicali City in the state of Baja California and the Yaqui River basin at Sonora State using three different methodologies. Results showed clear trends on temperature increase and occurrence of heat waves in both of the study zones using the three methodologies proposed. As result, some policy making suggestion are included in order to increase the adaptability of the studied regions to climate change, particularly related with heat wave occurrence.

Trends and Variability in Temperature Sensitivity of Lilac Flowering Phenology

NASA Astrophysics Data System (ADS)

Wang, Huanjiong; Dai, Junhu; Rutishauser, This; Gonsamo, Alemu; Wu, Chaoyang; Ge, Quansheng

2018-03-01

The responses of plant phenology to temperature variability have many consequences for ecological processes, agriculture, forestry, and human health. Temperature sensitivity (ST) of phenology could measure how and to what degree plant could phenologically track climate change. The long-term trends and spatial patterns in ST have been well studied for vegetative phenology such as leaf unfolding, but trends to be expected for reproductive phenology in the future remain unknown. Here we investigate trends and factors driving the temporal variation of ST of first bloom date (FBD). Using the long-term FBD records during 1963-2013 for common lilac (Syringa vulgaris) from 613 stations in Europe, we compared changes in ST from the beginning to the end of the study period. The Spearman partial correlations were used to assess the importance of four influencing factors. The results showed that the temporal changes in ST of FBD varied considerably among time scales. Mean ST decreased significantly by 0.92 days °C-1 from 1963-1972 to 2004-2013 (P < 0.01), but remained stable from 1963-1987 to 1989-2013. The strength of FBD and temperature relationship, the spring temperature variance, and winter chill all impact ST in an expected way at most stations. No consistent responses of ST on photoperiod were found. Our results imply that the trends and variability in ST of flowering phenology are driving by multiple factors and impacted by time scales. Continued efforts are still needed to further examine the flowering-temperature relationship for other plant species in other climates and environments using similar methods to our study.

Geo-processing Technology Trends in the Context of Ocean Mapping and Hydrographic Surveys that Support Future Marine Spatial Planning & Management.

NASA Astrophysics Data System (ADS)

Johnston, G.

2016-02-01

The current increased awareness in the oceans and marine areas has presented a challenge to the various institutions that work to gather data and manage information for the wider community of stakeholders. A number of trends and developments are becoming available to assist and further the national and international ocean mapping and monitoring initiatives. Some are technical in nature whilst others are related to the promotion and availability of information. This paper highlights a number of these key trends, their impact on ocean mapping and how we as scientists may be able to better engage and promote the need for good data and the potential added value and benefits to be derived. Whilst a significant amount of resources can be expended on acquiring and collecting high resolution bathymetric and hydrographic data there are new technologies to mitigate some of the bigger costs and with collaboration and cooperation greater benefits may be realized by the wider socio-economic communities who rely upon well governed and sustainable seas and oceans.

Wind speed variability over the Canary Islands, 1948-2014: focusing on trend differences at the land-ocean interface and below-above the trade-wind inversion layer

NASA Astrophysics Data System (ADS)

Azorin-Molina, Cesar; Menendez, Melisa; McVicar, Tim R.; Acevedo, Adrian; Vicente-Serrano, Sergio M.; Cuevas, Emilio; Minola, Lorenzo; Chen, Deliang

2017-08-01

This study simultaneously examines wind speed trends at the land-ocean interface, and below-above the trade-wind inversion layer in the Canary Islands and the surrounding Eastern North Atlantic Ocean: a key region for quantifying the variability of trade-winds and its response to large-scale atmospheric circulation changes. Two homogenized data sources are used: (1) observed wind speed from nine land-based stations (1981-2014), including one mountain weather station (Izaña) located above the trade-wind inversion layer; and (2) simulated wind speed from two atmospheric hindcasts over ocean (i.e., SeaWind I at 30 km for 1948-2014; and SeaWind II at 15 km for 1989-2014). The results revealed a widespread significant negative trend of trade-winds over ocean for 1948-2014, whereas no significant trends were detected for 1989-2014. For this recent period wind speed over land and ocean displayed the same multi-decadal variability and a distinct seasonal trend pattern with a strengthening (late spring and summer; significant in May and August) and weakening (winter-spring-autumn; significant in April and September) of trade-winds. Above the inversion layer at Izaña, we found a predominance of significant positive trends, indicating a decoupled variability and opposite wind speed trends when compared to those reported in boundary layer. The analysis of the Trade Wind Index (TWI), the North Atlantic Oscillation Index (NAOI) and the Eastern Atlantic Index (EAI) demonstrated significant correlations with the wind speed variability, revealing that the correlation patterns of the three indices showed a spatio-temporal complementarity in shaping wind speed trends across the Eastern North Atlantic.

Wind speed variability over the Canary Islands, 1948-2014: focusing on trend differences at the land-ocean interface and below-above the trade-wind inversion layer

NASA Astrophysics Data System (ADS)

Azorin-Molina, Cesar; Menendez, Melisa; McVicar, Tim R.; Acevedo, Adrian; Vicente-Serrano, Sergio M.; Cuevas, Emilio; Minola, Lorenzo; Chen, Deliang

2018-06-01

This study simultaneously examines wind speed trends at the land-ocean interface, and below-above the trade-wind inversion layer in the Canary Islands and the surrounding Eastern North Atlantic Ocean: a key region for quantifying the variability of trade-winds and its response to large-scale atmospheric circulation changes. Two homogenized data sources are used: (1) observed wind speed from nine land-based stations (1981-2014), including one mountain weather station (Izaña) located above the trade-wind inversion layer; and (2) simulated wind speed from two atmospheric hindcasts over ocean (i.e., SeaWind I at 30 km for 1948-2014; and SeaWind II at 15 km for 1989-2014). The results revealed a widespread significant negative trend of trade-winds over ocean for 1948-2014, whereas no significant trends were detected for 1989-2014. For this recent period wind speed over land and ocean displayed the same multi-decadal variability and a distinct seasonal trend pattern with a strengthening (late spring and summer; significant in May and August) and weakening (winter-spring-autumn; significant in April and September) of trade-winds. Above the inversion layer at Izaña, we found a predominance of significant positive trends, indicating a decoupled variability and opposite wind speed trends when compared to those reported in boundary layer. The analysis of the Trade Wind Index (TWI), the North Atlantic Oscillation Index (NAOI) and the Eastern Atlantic Index (EAI) demonstrated significant correlations with the wind speed variability, revealing that the correlation patterns of the three indices showed a spatio-temporal complementarity in shaping wind speed trends across the Eastern North Atlantic.

Long-term variations of SST and heat content in the Atlantic Ocean

NASA Astrophysics Data System (ADS)

Huonsou-gbo, Aubains; Servain, Jacques; Caniaux, Guy; Araujo, Moacyr; Bourlès, Bernard; Veleda, Doris

2015-04-01

Recent studies (eg. Wen et al. 2010; Servain et al. 2014) suggest that subsurface processes influence the interannual variability of sea surface temperature (SST) in the tropical Atlantic through the Meridional Overturning Circulation (MOC) with time lags of several months. In this study, we used observed SST and Ocean heat content to test such hypothesis during the period 1964-2013. First results indicate great similarities in the positive linear trends of monthly standardized anomalies of SST, upper ocean heat content (0-500m) and deeper ocean heat content (500-2000m) averaged over the whole Atlantic Ocean. Strong positive trends of SST and deeper heat content occurred in the equatorial Atlantic, while a strong positive trend of the upper heat content was observed in the northeast Atlantic. These positive trends were the highest during the last two decades. The lagged positive correlation patterns between upper heat content anomalies over the whole gridded Atlantic Ocean and SST anomalies averaged over the equatorial region (60°W-15°E; 10°N-10°S) show a slow temporal evolution, which is roughly in agreement with the upper MOC. More detailed works about the mechanism, as well as about the origin of the highest positive trend of the deeper heat content in the equatorial region, are presently under investigation. References Servain J., G. Caniaux, Y. K. Kouadio, M. J. McPhaden, M. Araujo (2014). Recent climatic trends in the tropical Atlantic. Climate Dynamics, Vol. 43, 3071-3089, DOI 10.1007/s00382-014-2168-7.

Understanding observed and simulated historical temperature trends in California

NASA Astrophysics Data System (ADS)

Bonfils, C. J.; Duffy, P. B.; Santer, B. D.; Lobell, D. B.; Wigley, T. M.

2006-12-01

In our study, we attempt 1) to improve our understanding of observed historical temperature trends and their underlying causes in the context of regional detection of climate change and 2) to identify possible neglected forcings and errors in the model response to imposed forcings at the origin of inconsistencies between models and observations. From eight different observational datasets, we estimate California-average temperature trends over 1950- 1999 and compare them to trends from a suite of IPCC control simulations of natural internal climate variability. We find that the substantial night-time warming occurring from January to September is inconsistent with model-based estimates of natural internal climate variability, and thus requires one or more external forcing agents to be explained. In contrast, we find that a significant day-time warming occurs only from January to March. Our confidence in these findings is increased because there is no evidence that the models systematically underestimate noise on interannual and decadal timescales. However, we also find that IPCC simulations of the 20th century that include combined anthropogenic and natural forcings are not able to reproduce such a pronounced seasonality of the trends. Our first hypothesis is that the warming of Californian winters over the second half of the twentieth century is associated with changes in large-scale atmospheric circulation that are likely to be human-induced. This circulation change is underestimated in the historical simulations, which may explain why the simulated warming of Californian winters is too weak. We also hypothesize that the lack of a detectable observed increase in summertime maximum temperature arises from a cooling associated with large-scale irrigation. This cooling may have, until now, counteracted the warming induced by increasing greenhouse gases and urbanization effects. Omitting to include this forcing in the simulations can result in overestimating the

Deep Ocean Warming Assessed from Altimeters, GRACE, 3 In-situ Measurements, and a Non-Boussinesq OGCM

NASA Technical Reports Server (NTRS)

Song, Y. Tony; Colberg, Frank

2011-01-01

Observational surveys have shown significant oceanic bottom water warming, but they are too spatially and temporally sporadic to quantify the deep ocean contribution to the present-day sea level rise (SLR). In this study, altimetry sea surface height (SSH), Gravity Recovery and Climate Experiment (GRACE) ocean mass, and in situ upper ocean (0-700 m) steric height have been assessed for their seasonal variability and trend maps. It is shown that neither the global mean nor the regional trends of altimetry SLR can be explained by the upper ocean steric height plus the GRACE ocean mass. A non-Boussinesq ocean general circulation model (OGCM), allowing the sea level to rise as a direct response to the heat added into the ocean, is then used to diagnose the deep ocean steric height. Constrained by sea surface temperature data and the top of atmosphere (TOA) radiation measurements, the model reproduces the observed upper ocean heat content well. Combining the modeled deep ocean steric height with observational upper ocean data gives the full depth steric height. Adding a GRACE-estimated mass trend, the data-model combination explains not only the altimetry global mean SLR but also its regional trends fairly well. The deep ocean warming is mostly prevalent in the Atlantic and Indian oceans, and along the Antarctic Circumpolar Current, suggesting a strong relation to the oceanic circulation and dynamics. Its comparison with available bottom water measurements shows reasonably good agreement, indicating that deep ocean warming below 700 m might have contributed 1.1 mm/yr to the global mean SLR or one-third of the altimeter-observed rate of 3.11 +/- 0.6 mm/yr over 1993-2008.

REGRESSION ANALYSIS OF SEA-SURFACE-TEMPERATURE PATTERNS FOR THE NORTH PACIFIC OCEAN.

DTIC Science & Technology

SEA WATER, *SURFACE TEMPERATURE, *OCEANOGRAPHIC DATA, PACIFIC OCEAN, REGRESSION ANALYSIS , STATISTICAL ANALYSIS, UNDERWATER EQUIPMENT, DETECTION, UNDERWATER COMMUNICATIONS, DISTRIBUTION, THERMAL PROPERTIES, COMPUTERS.

Are there evidences of altitudinal effects of air temperature trends in the European Alps 1820-2013?

NASA Astrophysics Data System (ADS)

Schoener, W.; Auer, I.; Chimani, B.; Garnekind, M.; Haslinger, K.

2013-12-01

We use the HISTALP data set (www.zamg.ac.at/histalp) in order to assess the elevation dependency of air temperature trends within the European Alps. The evidence of altitudinal effects of the climate warming (with higher sensitivity of high mountain regions to warming) is a key statement, or at least key hypothesis, in many studies. The high relevance of such statement resp. hypothesis is obvious if one consider the impacts resulting from such fact, such as snow- and glacier melting and related effects for mountain hydrology. The HISTALP data set stands out with respect to its series lengths and its high level of homogenisation. Interestingly, the HISTALP temperature data show no clear altitudinal dependency of warming or cooling trends within the period 1820-2013. Additionally, a rather homogenous temporal trend could be observed within the entire Greater Alpine Region (GAR). Because HISTALP include also air pressure and vapour pressure series, we could compare our measured air temperatures with mean-column air temperatures, computed by the barometric formula, which were derived from the independently measured air pressure data (using vapour pressure to account for the atmospheric water content) at low resp. high elevations. Computed mean column temperatures are in good agreement with observed temperatures, indicating generally homogenous temporal temperature trend behaviour at different elevations. Our finding contradicts several results from climate modelling attempts and also other studies investigating Alpine temperature trends. We conclude that, whereas modelling results are still limited in the assessment of altitudinal effect of temperature trends from missing atmospheric processes captured by the models, the difference of the trend behaviour compared to other analyses of instrumental air temperatures comes from the seasonal base taken as the basis for trend estimation. It appears that opposite trend in spring and autumn for the period 1980

Experimental study of temperature sensor for an ocean-going liquid hydrogen (LH2) carrier

NASA Astrophysics Data System (ADS)

Nakano, A.; Shimazaki, T.; Sekiya, M.; Shiozawa, H.; Aoyagi, A.; Ohtsuka, K.; Iwakiri, T.; Mikami, Z.; Sato, M.; Kinoshita, K.; Matsuoka, T.; Takayama, Y.; Yamamoto, K.

2018-04-01

The prototype temperature sensors for an ocean-going liquid hydrogen (LH2) carrier were manufactured by way of trial. All of the sensors adopted Platinum 1000 (PT-1000) resistance thermometer elements. Various configurations of preproduction temperature sensors were tested in AIST's LH2 test facility. In the experiments, a PT-1000 resistance thermometer, calibrated at the National Metrology Institute of Japan at AIST, was used as the standard thermometer. The temperatures measured by the preproduction sensors were compared with the temperatures measured by the standard thermometer, and the measurement accuracy of the temperature sensors in LH2 was investigated and discussed. It was confirmed that the measurement accuracies of the preproduction temperature sensors were within ±50 mK, which is the required measurement accuracy for a technical demonstration ocean-going LH2 carrier.

A Note on the Relationship of Temperature and Water Vapor over Oceans, as well as the Sea Surface Temperature Impact

NASA Technical Reports Server (NTRS)

Shie, C.-L.; Tao, W.-K.; Simpson, J.

2005-01-01

This note follows up on a recent study by Shie et al. (2005) and extends the investigation of the domain-averaged moisture-temperature (Q-T) relationship from the Tropics (i.e., the previous study) to the tropical Pacific, Atlantic and Indian Oceans. The Q and T data examined in this study are obtained from the GEOS-3 [Goddard Earth Observing System Version-3] global re-analysis monthly products. Similar to what was found earlier in the Tropics, Q is also found to increase with T over the entire oceanic region; however, Q increases faster with T over oceans than over the Tropics. The Q-T distribution for the Tropics is in a quasi-linear relationship, which is embedded in a global Q-T distribution that is, however, in a more complex curvilinear relationship. The Q-T distribution over the oceanic regions seems to fall within the lower bound (ie., the relatively colder and driver regime) of the tropical Q-T distribution. T over oceans is also found increasing with SST (sea surface temperature), which seemingly implies that an air mass might have gained heat more readily from a warmer ocean as compared to a colder ocean. Q is also found to increase with SST in a manner that quantitatively resembles an earlier finding by Stevens (1990). We also found that relative humidity exhibits similar behaviors for oceanic and tropical regions, respectively, i.e., it increases with both SST and T over oceans and increases with T in the Tropics (Shie et al. 2005). All these similar features found between oceanic and tropical regions seem to inform us that oceans occupy most of the Tropics and so play a key role in determining what have happened in the Tropics.

Subtropical Arctic Ocean temperatures during the Palaeocene/Eocene thermal maximum

USGS Publications Warehouse

Sluijs, A.; Schouten, S.; Pagani, M.; Woltering, M.; Brinkhuis, H.; Damste, J.S.S.; Dickens, G.R.; Huber, M.; Reichart, G.-J.; Stein, R.; Matthiessen, J.; Lourens, L.J.; Pedentchouk, N.; Backman, J.; Moran, K.; Clemens, S.; Cronin, T.; Eynaud, F.; Gattacceca, J.; Jakobsson, M.; Jordan, R.; Kaminski, M.; King, J.; Koc, N.; Martinez, N.C.; McInroy, D.; Moore, T.C.; O'Regan, M.; Onodera, J.; Palike, H.; Rea, B.; Rio, D.; Sakamoto, T.; Smith, D.C.; St John, K.E.K.; Suto, I.; Suzuki, N.; Takahashi, K.; Watanabe, M. E.; Yamamoto, M.

2006-01-01

The Palaeocene/Eocene thermal maximum, ???55 million years ago, was a brief period of widespread, extreme climatic warming, that was associated with massive atmospheric greenhouse gas input. Although aspects of the resulting environmental changes are well documented at low latitudes, no data were available to quantify simultaneous changes in the Arctic region. Here we identify the Palaeocene/Eocene thermal maximum in a marine sedimentary sequence obtained during the Arctic Coring Expedition. We show that sea surface temperatures near the North Pole increased from ???18??C to over 23??C during this event. Such warm values imply the absence of ice and thus exclude the influence of ice-albedo feedbacks on this Arctic warming. At the same time, sea level rose while anoxic and euxinic conditions developed in the ocean's bottom waters and photic zone, respectively. Increasing temperature and sea level match expectations based on palaeoclimate model simulations, but the absolute polar temperatures that we derive before, during and after the event are more than 10??C warmer than those model-predicted. This suggests that higher-than-modern greenhouse gas concentrations must have operated in conjunction with other feedback mechanisms-perhaps polar stratospheric clouds or hurricane-induced ocean mixing-to amplify early Palaeogene polar temperatures. ?? 2006 Nature Publishing Group.

Subtropical Arctic Ocean temperatures during the Palaeocene/Eocene thermal maximum.

PubMed

Sluijs, Appy; Schouten, Stefan; Pagani, Mark; Woltering, Martijn; Brinkhuis, Henk; Sinninghe Damsté, Jaap S; Dickens, Gerald R; Huber, Matthew; Reichart, Gert-Jan; Stein, Ruediger; Matthiessen, Jens; Lourens, Lucas J; Pedentchouk, Nikolai; Backman, Jan; Moran, Kathryn

2006-06-01

The Palaeocene/Eocene thermal maximum, approximately 55 million years ago, was a brief period of widespread, extreme climatic warming, that was associated with massive atmospheric greenhouse gas input. Although aspects of the resulting environmental changes are well documented at low latitudes, no data were available to quantify simultaneous changes in the Arctic region. Here we identify the Palaeocene/Eocene thermal maximum in a marine sedimentary sequence obtained during the Arctic Coring Expedition. We show that sea surface temperatures near the North Pole increased from 18 degrees C to over 23 degrees C during this event. Such warm values imply the absence of ice and thus exclude the influence of ice-albedo feedbacks on this Arctic warming. At the same time, sea level rose while anoxic and euxinic conditions developed in the ocean's bottom waters and photic zone, respectively. Increasing temperature and sea level match expectations based on palaeoclimate model simulations, but the absolute polar temperatures that we derive before, during and after the event are more than 10 degrees C warmer than those model-predicted. This suggests that higher-than-modern greenhouse gas concentrations must have operated in conjunction with other feedback mechanisms--perhaps polar stratospheric clouds or hurricane-induced ocean mixing--to amplify early Palaeogene polar temperatures.

An analysis of surface air temperature trends and variability along the Andes

NASA Astrophysics Data System (ADS)

Franquist, Eric S.

Climate change is difficult to study in mountainous regions such as the Andes since steep changes in elevation cannot always be resolved by climate models. However, it is important to examine temperature trends in this region as rises in surface air temperature are leading to the melting of tropical glaciers. Local communities rely on the glacier-fed streamflow to get their water for drinking, irrigation, and livestock. Moreover, communities also rely on the tourism of hikers who come to the region to view the glaciers. As the temperatures increase, these glaciers are no longer in equilibrium with their current climate and are receding rapidly and decreasing the streamflow. This thesis examines surface air temperature from 858 weather stations across Ecuador, Peru, and Chile in order to analyze changes in trends and variability. Three time periods were studied: 1961--1990, 1971--2000, and 1981--2010. The greatest warming occurred during the period of 1971--2000 with 92% of the stations experiencing positive trends with a mean of 0.24°C/decade. There was a clear shift toward cooler temperatures at all latitudes and below elevations of 500 m during the most recent time period studied (1981--2010). Station temperatures were more strongly correlated with the El Nino Southern Oscillation (ENSO), than the Pacific Decadal Oscillation (PDO), and the Southern Annular Mode (SAM). A principal component analysis confirmed ENSO as the main contributor of variability with the most influence in the lower latitudes. There were clear multidecadal changes in correlation strength for the PDO. The PDO contributed the most to the increases in station temperature trends during the 1961--1990 period, consistent with the PDO shift to the positive phase in the middle of this period. There were many strong positive trends at individual stations during the 1971--2000 period; however, these trends could not fully be attributed to ENSO, PDO, or SAM, indicating anthropogenic effects of

Trends of urban surface temperature and heat island characteristics in the Mediterranean

NASA Astrophysics Data System (ADS)

Benas, Nikolaos; Chrysoulakis, Nektarios; Cartalis, Constantinos

2017-11-01

Urban air temperature studies usually focus on the urban canopy heat island phenomenon, whereby the city center experiences higher near surface air temperatures compared to its surrounding non-urban areas. The Land Surface Temperature (LST) is used instead of urban air temperature to identify the Surface Urban Heat Island (SUHI). In this study, the nighttime LST and SUHI characteristics and trends in the seventeen largest Mediterranean cities were investigated, by analyzing satellite observations for the period 2001-2012. SUHI averages and trends were based on an innovative approach of comparing urban pixels to randomly selected non-urban pixels, which carries the potential to better standardize satellite-derived SUHI estimations. A positive trend for both LST and SUHI for the majority of the examined cities was documented. Furthermore, a 0.1 °C decade-1 increase in urban LST corresponded to an increase in SUHI by about 0.04 °C decade-1. A longitudinal differentiation was found in the urban LST trends, with higher positive values appearing in the eastern Mediterranean. Examination of urban infrastructure and development factors during the same period revealed correlations with SUHI trends, which can be used to explain differences among cities. However, the majority of the cities examined show considerably increased trends in terms of the enhancement of SUHI. These findings are considered important so as to promote sustainable urbanization, as well as to support the development of heat island adaptation and mitigation plans in the Mediterranean.

Climatic trends over Ethiopia: regional signals and drivers

USGS Publications Warehouse

Jury, Mark R.; Funk, Christopher C.

2013-01-01

This study analyses observed and projected climatic trends over Ethiopia, through analysis of temperature and rainfall records and related meteorological fields. The observed datasets include gridded station records and reanalysis products; while projected trends are analysed from coupled model simulations drawn from the IPCC 4th Assessment. Upward trends in air temperature of + 0.03 °C year−1 and downward trends in rainfall of − 0.4 mm month−1 year−1 have been observed over Ethiopia's southwestern region in the period 1948-2006. These trends are projected to continue to 2050 according to the Geophysical Fluid Dynamics Lab model using the A1B scenario. Large scale forcing derives from the West Indian Ocean where significant warming and increased rainfall are found. Anticyclonic circulations have strengthened over northern and southern Africa, limiting moisture transport from the Gulf of Guinea and Congo. Changes in the regional Walker and Hadley circulations modulate the observed and projected climatic trends. Comparing past and future patterns, the key features spread westward from Ethiopia across the Sahel and serve as an early warning of potential impacts.

Land use/land cover change effects on temperature trends at U.S. Climate Normals stations

USGS Publications Warehouse

Hale, R.C.; Gallo, K.P.; Owen, T.W.; Loveland, Thomas R.

2006-01-01

Alterations in land use/land cover (LULC) in areas near meteorological observation stations can influence the measurement of climatological variables such as temperature. Urbanization near climate stations has been the focus of considerable research attention, however conversions between non-urban LULC classes may also have an impact. In this study, trends of minimum, maximum, and average temperature at 366 U.S. Climate Normals stations are analyzed based on changes in LULC defined by the U.S. Land Cover Trends Project. Results indicate relatively few significant temperature trends before periods of greatest LULC change, and these are generally evenly divided between warming and cooling trends. In contrast, after the period of greatest LULC change was observed, 95% of the stations that exhibited significant trends (minimum, maximum, or mean temperature) displayed warming trends. Copyriht 2006 by the American Geophysical Union.

Variability of Coastal and Ocean Water Temperature in the Upper 700 m along the Western Iberian Peninsula from 1975 to 2006

PubMed Central

Santos, Fran; Gómez-Gesteira, Moncho; deCastro, Maite; Álvarez, Inés

2012-01-01

Temperature is observed to have different trends at coastal and ocean locations along the western Iberian Peninsula from 1975 to 2006, which corresponds to the last warming period in the area under study. The analysis was carried out by means of the Simple Ocean Data Assimilation (SODA). Reanalysis data are available at monthly scale with a horizontal resolution of 0.5°×0.5° and a vertical resolution of 40 levels, which allows obtaining information beneath the sea surface. Only the first 21 vertical levels (from 5.0 m to 729.35 m) were considered here, since the most important changes in heat content observed for the world ocean during the last decades, correspond to the upper 700 m. Warming was observed to be considerably higher at ocean locations than at coastal ones. Ocean warming ranged from values on the order of 0.3°C dec−1 near surface to less than 0.1°C dec−1 at 500 m, while coastal warming showed values close to 0.2°C dec−1 near surface, decreasing rapidly below 0.1°C dec−1 for depths on the order of 50 m. The heat content anomaly for the upper 700 m, showed a sharp increase from coast (0.46 Wm−2) to ocean (1.59 Wm−2). The difference between coastal and ocean values was related to the presence of coastal upwelling, which partially inhibits the warming from surface of near shore water. PMID:23226533

Closing the Seasonal Ocean Surface Temperature Balance in the Eastern Tropical Oceans from Remote Sensing and Model Reanalyses

NASA Technical Reports Server (NTRS)

Roberts, J. Brent; Clayson, C. A.

2012-01-01

Residual forcing necessary to close the MLTB on seasonal time scales are largest in regions of strongest surface heat flux forcing. Identifying the dominant source of error - surface heat flux error, mixed layer depth estimation, ocean dynamical forcing - remains a challenge in the eastern tropical oceans where ocean processes are very active. Improved sub-surface observations are necessary to better constrain errors. 1. Mixed layer depth evolution is critical to the seasonal evolution of mixed layer temperatures. It determines the inertia of the mixed layer, and scales the sensitivity of the MLTB to errors in surface heat flux and ocean dynamical forcing. This role produces timing impacts for errors in SST prediction. 2. Errors in the MLTB are larger than the historical 10Wm-2 target accuracy. In some regions, a larger accuracy can be tolerated if the goal is to resolve the seasonal SST cycle.

Change features and regional distribution of temperature trend and variability joint mode in mainland China

NASA Astrophysics Data System (ADS)

Chen, Xi; Li, Ning; Zhang, Zhengtao; Feng, Jieling; Wang, Ye

2018-05-01

Adaption for temperature should be suitable to local conditions for regional differences in temperature change features. This paper proposed to utilize nine temperature modes that joint the trend (increasing/decreasing/unchanged) with variability (intensifying/weakening/unchanged) to investigate features of temperature change in mainland China. Monthly temperature data over the period 1960-2013 were obtained from 522 national basic and reference meteorological stations. Here, temperature trend (TT) was reflected by the trend of mean annual temperature (MAT) and the uptrend (downtrend) of inter-monthly sliding standard deviation (SSD) series with a sliding length of 29 years (348 months) was used for representing the intensification (weakening) of temperature variability (TV). The Mann-Kendall method and the least squares method were applied to assess the significance and quantify the magnitude of trend in MAT and SSD time series, respectively. The results show that there is a consistent warming trend throughout the country except for only three stations in which a cooling trend is identified. Moreover, the overall increasing rate in the north of 35° N is the highest, over 0.4 °C/decade for most stations. TV is weakened for almost 98% of the stations, indicating the low instability of temperature at a national scale. Finally, temperature mode (TM), for more than 90% of the stations, is the combination of an increasing TT with a weakened TV (mode 8). So, it is more important for people to adapt to the increasing temperature in these regions. Compared to using annual temperature data to calculate SSD, monthly data can accurately reflect the inter-monthly change of temperature and reserve more initial characteristics of temperature.

Oceans Melting Greenland (OMG): 2017 Observations and the First Look at Yearly Ocean/Ice Changes

NASA Astrophysics Data System (ADS)

Willis, J. K.; Rignot, E. J.; Fenty, I. G.; Khazendar, A.; Moller, D.; Tinto, K. J.; Morison, J.; Schodlok, M.; Thompson, A. F.; Fukumori, I.; Holland, D.; Forsberg, R.; Jakobsson, M.; Dinardo, S. J.

2017-12-01

Oceans Melting Greenland (OMG) is an airborne NASA Mission to investigate the role of the oceans in ice loss around the margins of the Greenland Ice Sheet. A five-year campaign, OMG will directly measure ocean warming and glacier retreat around all of Greenland. By relating these two, we will explore one of the most pressing open questions about how climate change drives sea level rise: How quickly are the warming oceans melting the Greenland Ice Sheet from the edges? This year, OMG collected its second set of both elevation maps of marine terminating glaciers and ocean temperature and salinity profiles around all of Greenland. This give us our first look at year-to-year changes in both ice volume at the margins, as well as the volume and extent of warm, salty Atlantic water present on the continental shelf. In addition, we will compare recent data in east Greenland waters with historical ocean observations that suggest a long-term warming trend there. Finally, we will briefly review the multi-beam sonar and airborne gravity campaigns—both of which were completed last year—and the dramatic improvement they had on bathymetry maps over the continental shelf around Greenland.

Problems in evaluating regional and local trends in temperature: An example from eastern Colorado, USA

USGS Publications Warehouse

Pielke, R.A.; Stohlgren, T.; Schell, L.; Parton, W.; Doesken, N.; Redmond, K.; Moeny, J.; McKee, T.; Kittel, T.G.F.

2002-01-01

We evaluated long-term trends in average maximum and minimum temperatures, threshold temperatures, and growing season in eastern Colorado, USA, to explore the potential shortcomings of many climate-change studies that either: (1) generalize regional patterns from single stations, single seasons, or a few parameters over short duration from averaging dissimilar stations: or (2) generalize an average regional pattern from coarse-scale general circulation models. Based on 11 weather stations, some trends were weakly regionally consistent with previous studies of night-time temperature warming. Long-term (80 + years) mean minimum temperatures increased significantly (P < 0.2) in about half the stations in winter, spring, and autumn and six stations had significant decreases in the number of days per year with temperatures ??? - 17.8 ??C (???0??F). However, spatial and temporal variation in the direction of change was enormous for all the other weather parameters tested, and, in the majority of tests, few stations showed significant trends (even at P < 0.2). In summer, four stations had significant increases and three stations had significant decreases in minimum temperatures, producing a strongly mixed regional signal. Trends in maximum temperature varied seasonally and geographically, as did trends in threshold temperature days ???32.2??C (???90??F) or days ???37.8??C (???100??F). There was evidence of a subregional cooling in autumn's maximum temperatures, with five stations showing significant decreasing trends. There were many geographic anomalies where neighbouring weather stations differed greatly in the magnitude of change or where they had significant and opposite trends. We conclude that sub-regional spatial and seasonal variation cannot be ignored when evaluating the direction and magnitude of climate change. It is unlikely that one or a few weather stations are representative of regional climate trends, and equally unlikely that regionally projected climate

A Crystallization-Temperature Profile Through Paleo-Oceanic Crust (Wadi Gideah Transect, Oman Ophiolite): Application of the REE-in-Plagioclase-Clinopyroxene Partitioning Thermometer

NASA Astrophysics Data System (ADS)

Mueller, S.; Hasenclever, J.; Garbe-Schönberg, D.; Koepke, J.; Hoernle, K.

2017-12-01

The accretion mechanisms forming oceanic crust at fast spreading ridges are still under controversial discussion. Thermal, petrological, and geochemical observations predict different end-member models, i.e., the gabbro glacier and the sheeted sill model. They all bear implications for heat transport, temperature distribution, mode of crystallization and hydrothermal heat removal over crustal depth. In a typical MOR setting, temperature is the key factor driving partitioning of incompatible elements during crystallization. LA-ICP-MS data for co-genetic plagioclase and clinopyroxene in gabbros along a transect through the plutonic section of paleo-oceanic crust (Wadi Gideah Transect, Oman ophiolite) reveal that REE partitioning coefficients are relatively constant in the layered gabbro section but increase for the overlying foliated gabbros, with an enhanced offset towards HREEs. Along with a systematic enrichment of REE's with crustal height, these trends are consistent with a system dominated by in-situ crystallization for the lower gabbros and a change in crystallization mode for the upper gabbros. Sun and Liang (2017) used experimental REE partitioning data for calibrating a new REE-in-plagioclase-clinopyroxene thermometer that we used here for establishing the first crystallization-temperature depth profile through oceanic crust that facilitates a direct comparison with thermal models of crustal accretion. Our results indicate crystallization temperatures of about 1220±8°C for the layered gabbros and lower temperatures of 1175±8°C for the foliated gabbros and a thermal minimum above the layered-to-foliated gabbro transition. Our findings are consistent with a hybrid accretion model for the oceanic crust. The thermal minimum is assumed to represent a zone where the descending crystal mushes originating from the axial melt lens meet with mushes that have crystallized in situ. These results can be used to verify and test thermal models (e.g., Maclennan et al

Temperature trends and Urban Heat Island intensity mapping of the Las Vegas valley area

NASA Astrophysics Data System (ADS)

Black, Adam Leland

Modified urban climate regions that are warmer than rural areas at night are referred to as Urban Heat Islands or UHI. Islands of warmer air over a city can be 12 degrees Celsius greater than the surrounding cooler air. The exponential growth in Las Vegas for the last two decades provides an opportunity to detect gradual temperature changes influenced by an increasing presence of urban materials. This thesis compares ground based thermometric observations and satellite based remote sensing temperature observations to identify temperature trends and UHI areas caused by urban development. Analysis of temperature trends between 2000 and 2010 at ground weather stations has revealed a general cooling trend in the Las Vegas region. Results show that urban development accompanied by increased vegetation has a cooling effect in arid climates. Analysis of long term temperature trends at McCarran and Nellis weather stations show 2.4 K and 1.2 K rise in temperature over the last 60 years. The ground weather station temperature data is related to the land surface temperature images from the Landsat Thematic Mapper to estimate and evaluate urban heat island intensity for Las Vegas. Results show that spatial and temporal trends of temperature are related to the gradual change in urban landcover. UHI are mainly observed at the airport and in the industrial areas. This research provides useful insight into the temporal behavior of the Las Vegas area.

Ocean products delivered by the Mercator Ocean Service Department

NASA Astrophysics Data System (ADS)

Crosnier, L.; Durand, E.; Soulat, F.; Messal, F.; Buarque, S.; Toumazou, V.; Landes, V.; Drevillon, M.; Lellouche, J.

2008-12-01

The newly created Service Department at Mercator Ocean is now offering various services for academic and private ocean applications. Mercator Ocean runs operationally ocean forecast systems for the Global and North Atlantic Ocean. These systems are based on an ocean general circulation model NEMO as well as on data assimilation of sea level anomalies, sea surface temperature and temperature and salinity vertical profiles. Three dimensional ocean fields of temperature, salinity and currents are updated and available weekly, including analysis and 2 weeks forecast fields. The Mercator Ocean service department is now offering a wide range of ocean derived products. This presentation will display some of the various products delivered in the framework of academic and private ocean applications: " Monitoring of the ocean current at the surface and at depth in several geographical areas for offshore oil platform, for offshore satellite launch platform, for transatlantic sailing or rowing boat races. " Monitoring of ocean climate indicators (Coral bleaching...) for marine reserve survey; " Monitoring of upwelling systems for fisheries; " Monitoring of the ocean heat content for tropical cyclone monitoring. " Monitoring of the ocean temperature/salinity and currents to guide research vessels during scientific cruises. The Mercator Ocean products catalogue will grow wider in the coming years, especially in the framework of the European GMES MyOcean project (FP7).

Extreme temperature trends in major cropping systems and their relation to agricultural land use change

NASA Astrophysics Data System (ADS)

Mueller, N. D.; Butler, E. E.; McKinnon, K. A.; Rhines, A. N.; Tingley, M.; Siebert, S.; Holbrook, N. M.; Huybers, P. J.

2015-12-01

High temperature extremes during the growing season can reduce agricultural production. At the same time, agricultural practices can modify temperatures by altering the surface energy budget. Here we investigate growing season climate trends in major cropping systems and their relationship with agricultural land use change. In the US Midwest, 100-year trends exhibit a transition towards more favorable conditions, with cooler summer temperature extremes and increased precipitation. Statistically significant correspondence is found between the cooling pattern and trends in cropland intensification, as well as with trends towards greater irrigated land over a small subset of the domain. Land conversion to cropland, often considered an important influence on historical temperatures, is not significantly associated with cooling. We suggest that cooling is primarily associated with agricultural intensification increasing the potential for evapotranspiration, consistent with our finding that cooling trends are greatest for the highest temperature percentiles, and that increased evapotranspiration generally leads to greater precipitation. Temperatures over rainfed croplands show no cooling trend during drought conditions, consistent with evapotranspiration requiring adequate soil moisture, and implying that modern drought events feature greater warming as baseline cooler temperatures revert to historically high extremes. Preliminary results indicate these relationships between temperature extremes, irrigation, and intensification are also observed in other major summer cropping systems, including northeast China, Argentina, and the Canadian Prairies.

Differences in coastal and oceanic SST trends north of Yucatan Peninsula

NASA Astrophysics Data System (ADS)

Varela, R.; Costoya, X.; Enriquez, C.; Santos, F.; Gómez-Gesteira, M.

2018-06-01

The coastal area north of Yucatan has experienced a cooling SST trend from 1982 to 2015 during the upwelling season (May-September) that contrasts with the warming observed at the adjacent ocean area. Different drivers were analyzed to identify the possible causes of that unusual coastal cooling. Changes in coastal upwelling and in sea-atmosphere heat fluxes are not consistent with the observed coastal cooling. The eastward shift of the Yucatan Current observed over the last decades is hypothesized as the most probable cause of coastal cooling. This shift enhances the vertical transport of cold deeper water to the continental shelf from where it is pumped to the surface by upwelling favorable westerly winds.

Ocean climate and seal condition.

PubMed

Le Boeuf, Burney J; Crocker, Daniel E

2005-03-28

The condition of many marine mammals varies with fluctuations in productivity and food supply in the ocean basin where they forage. Prey is impacted by physical environmental variables such as cyclic warming trends. The weaning weight of northern elephant seal pups, Mirounga angustirostris, being closely linked to maternal condition, indirectly reflects prey availability and foraging success of pregnant females in deep waters of the northeastern Pacific. The aim of this study was to examine the effect of ocean climate on foraging success in this deep-diving marine mammal over the course of three decades, using cohort weaning weight as the principal metric of successful resource accrual. The mean annual weaning weight of pups declined from 1975 to the late 1990s, a period characterized by a large-scale, basin-wide warm decadal regime that included multiple strong or long-duration El Niños; and increased with a return to a cool decadal regime from about 1999 to 2004. Increased foraging effort and decreased mass gain of adult females, indicative of reduced foraging success and nutritional stress, were associated with high ocean temperatures. Despite ranging widely and foraging deeply in cold waters beyond coastal thermoclines in the northeastern Pacific, elephant seals are impacted significantly by ocean thermal dynamics. Ocean warming redistributes prey decreasing foraging success of females, which in turn leads to lower weaning mass of pups. Annual fluctuations in weaning mass, in turn, reflect the foraging success of females during the year prior to giving birth and signals changes in ocean temperature cycles.

Understanding Arctic Surface Temperature Differences in Reanalyses

NASA Technical Reports Server (NTRS)

Cullather, Richard; Zhao, Bin; Shuman, Christopher; Nowicki, Sophie

2017-01-01

Reanalyses in the Arctic are widely used for model evaluation and for understanding contemporary climate change. Nevertheless, differences among reanalyses in fundamental meteorological variables including surface air temperature are large. A review of surface temperature differences is presented with a particular focus on differences in contemporary reanalyses. An important consideration is the significant differences in Arctic surfaces, including the central Arctic Ocean, the Greenland Ice Sheet, and non-glaciated land. While there is significant correlation among reanalyses in annual time series, there is substantial disagreement in mean values. For the period 1980-2013, the trend in annual temperature ranges from 0.3 to 0.7K per decade. Over the central Arctic Ocean, differences in mean values and trends are larger. Most of the uncertainty is associated with winter months. This is likely associated with the constraint imposed by melting processes (i.e. 0 deg. Celsius), rather than seasonal changes to the observing system.

Variability and trends in surface seawater pCO2 and CO2 flux in the Pacific Ocean

NASA Astrophysics Data System (ADS)

Sutton, A. J.; Wanninkhof, R.; Sabine, C. L.; Feely, R. A.; Cronin, M. F.; Weller, R. A.

2017-06-01

Variability and change in the ocean sink of anthropogenic carbon dioxide (CO2) have implications for future climate and ocean acidification. Measurements of surface seawater CO2 partial pressure (pCO2) and wind speed from moored platforms are used to calculate high-resolution CO2 flux time series. Here we use the moored CO2 fluxes to examine variability and its drivers over a range of time scales at four locations in the Pacific Ocean. There are significant surface seawater pCO2, salinity, and wind speed trends in the North Pacific subtropical gyre, especially during winter and spring, which reduce CO2 uptake over the 10 year record of this study. Starting in late 2013, elevated seawater pCO2 values driven by warm anomalies cause this region to be a net annual CO2 source for the first time in the observational record, demonstrating how climate forcing can influence the timing of an ocean region shift from CO2 sink to source.

Simulations of Eurasian winter temperature trends in coupled and uncoupled CFSv2

NASA Astrophysics Data System (ADS)

Collow, Thomas W.; Wang, Wanqiu; Kumar, Arun

2018-01-01

Conflicting results have been presented regarding the link between Arctic sea-ice loss and midlatitude cooling, particularly over Eurasia. This study analyzes uncoupled (atmosphere-only) and coupled (ocean-atmosphere) simulations by the Climate Forecast System, version 2 (CFSv2), to examine this linkage during the Northern Hemisphere winter, focusing on the simulation of the observed surface cooling trend over Eurasia during the last three decades. The uncoupled simulations are Atmospheric Model Intercomparison Project (AMIP) runs forced with mean seasonal cycles of sea surface temperature (SST) and sea ice, using combinations of SST and sea ice from different time periods to assess the role that each plays individually, and to assess the role of atmospheric internal variability. Coupled runs are used to further investigate the role of internal variability via the analysis of initialized predictions and the evolution of the forecast with lead time. The AMIP simulations show a mean warming response over Eurasia due to SST changes, but little response to changes in sea ice. Individual runs simulate cooler periods over Eurasia, and this is shown to be concurrent with a stronger Siberian high and warming over Greenland. No substantial differences in the variability of Eurasian surface temperatures are found between the different model configurations. In the coupled runs, the region of significant warming over Eurasia is small at short leads, but increases at longer leads. It is concluded that, although the models have some capability in highlighting the temperature variability over Eurasia, the observed cooling may still be a consequence of internal variability.

Global and regional trends of aerosol optical depth over land and ocean using SeaWiFS measurements from 1997 to 2010

NASA Astrophysics Data System (ADS)

Hsu, N. C.; Gautam, R.; Sayer, A. M.; Bettenhausen, C.; Li, C.; Jeong, M. J.; Tsay, S.-C.; Holben, B. N.

2012-09-01

Both sensor calibration and satellite retrieval algorithm play an important role in the ability to determine accurately long-term trends from satellite data. Owing to the unprecedented accuracy and long-term stability of its radiometric calibration, SeaWiFS measurements exhibit minimal uncertainty with respect to sensor calibration. In this study, we take advantage of this well-calibrated set of measurements by applying a newly-developed aerosol optical depth (AOD) retrieval algorithm over land and ocean to investigate the distribution of AOD, and to identify emerging patterns and trends in global and regional aerosol loading during its 13-yr mission. Our correlation analysis between climatic indices (such as ENSO) and AOD suggests strong relationships for Saharan dust export as well as biomass-burning activity in the tropics, associated with large-scale feedbacks. The results also indicate that the averaged AOD trend over global ocean is weakly positive from 1998 to 2010 and comparable to that observed by MODIS but opposite in sign to that observed by AVHRR during overlapping years. On regional scales, distinct tendencies are found for different regions associated with natural and anthropogenic aerosol emission and transport. For example, large upward trends are found over the Arabian Peninsula that indicate a strengthening of the seasonal cycle of dust emission and transport processes over the whole region as well as over downwind oceanic regions. In contrast, a negative-neutral tendency is observed over the desert/arid Saharan region as well as in the associated dust outflow over the north Atlantic. Additionally, we found decreasing trends over the eastern US and Europe, and increasing trends over countries such as China and India that are experiencing rapid economic development. In general, these results are consistent with those derived from ground-based AERONET measurements.

Is the distribution of nitrogen-fixing cyanobacteria in the oceans related to temperature?

PubMed

Stal, Lucas J

2009-07-01

Approximately 50% of the global natural fixation of nitrogen occurs in the oceans supporting a considerable part of the new primary production. Virtually all nitrogen fixation in the ocean occurs in the tropics and subtropics where the surface water temperature is 25°C or higher. It is attributed almost exclusively to cyanobacteria. This is remarkable firstly because diazotrophic cyanobacteria are found in other environments irrespective of temperature and secondly because primary production in temperate and cold oceans is generally limited by nitrogen. Cyanobacteria are oxygenic phototrophic organisms that evolved a variety of strategies protecting nitrogenase from oxygen inactivation. Free-living diazotrophic cyanobacteria in the ocean are of the non-heterocystous type, namely the filamentous Trichodesmium and the unicellular groups A-C. I will argue that warm water is a prerequisite for these diazotrophic organisms because of the low-oxygen solubility and high rates of respiration allowing the organism to maintain anoxic conditions in the nitrogen-fixing cell. Heterocystous cyanobacteria are abundant in freshwater and brackish environments in all climatic zones. The heterocyst cell envelope is a tuneable gas diffusion barrier that optimizes the influx of both oxygen and nitrogen, while maintaining anoxic conditions inside the cell. It is not known why heterocystous cyanobacteria are absent from the temperate and cold oceans and seas.

Mediterranean Ocean Colour Chlorophyll Trends.

PubMed

Colella, Simone; Falcini, Federico; Rinaldi, Eleonora; Sammartino, Michela; Santoleri, Rosalia

2016-01-01

In being at the base of the marine food web, phytoplankton is particularly important for marine ecosystem functioning (e.g., biodiversity). Strong anthropization, over-exploitation of natural resources, and climate change affect the natural amount of phytoplankton and, therefore, represent a continuous threat to the biodiversity in marine waters. In particular, a concerning risks for coastal waters is the increase in nutrient inputs of terrestrial/anthropogenic origin that can lead to undesirable modifications of phytoplankton concentration (i.e., eutrophication). Monitoring chlorophyll (Chl) concentration, which is a proxy of phytoplankton biomass, is an efficient tool for recording and understanding the response of the marine ecosystem to human pressures and thus for detecting eutrophication. Here, we compute Chl trends over the Mediterranean Sea by using satellite data, also highlighting the fact that remote sensing may represent an efficient and reliable solution to synoptically control the "good environmental status" (i.e., the Marine Directive to achieve Good Environmental Status of EU marine waters by 2020) and to assess the application of international regulations and environmental directives. Our methodology includes the use of an ad hoc regional (i.e., Mediterranean) algorithm for Chl concentration retrieval, also accounting for the difference between offshore (i.e., Case I) and coastal (i.e., Case II) waters. We apply the Mann-Kendall test and the Sens's method for trend estimation to the Chl concentration de-seasonalized monthly time series, as obtained from the X-11 technique. We also provide a preliminary analysis of some particular trends by evaluating their associated inter-annual variability. The high spatial resolution of our approach allows a clear identification of intense trends in those coastal waters that are affected by river outflows. We do not attempt to attribute the observed trends to specific anthropogenic events. However, the trends

Testing Predictions of Continental Insulation using Oceanic Crustal Thicknesses

NASA Astrophysics Data System (ADS)

Hoggard, Mark; Shorttle, Oliver; White, Nicky

2016-04-01

The thermal blanketing effect of continental crust has been predicted to lead to elevated temperatures within the upper mantle beneath supercontinents. Initial break-up is associated with increased magmatism and the generation of flood basalts. Continued rifting and sea-floor spreading lead to a steady reduction of this thermal anomaly. Recently, evidence in support of this behaviour has come from the major element geochemistry of mid-ocean ridge basalts, which suggest excess rifting temperatures of ˜ 150 °C that decay over ˜ 100 Ma. We have collated a global inventory of ˜ 1000 seismic reflection profiles and ˜ 500 wide-angle refraction experiments from the oceanic realm. Data are predominantly located along passive margins, but there are also multiple surveys in the centres of the major oceanic basins. Oceanic crustal thickness has been mapped, taking care to avoid areas of secondary magmatic thickening near seamounts or later thinning such as across transform faults. These crustal thicknesses are a proxy for mantle potential temperature at the time of melt formation beneath a mid-ocean ridge system, allowing us to quantify the amplitude and duration of thermal anomalies generated beneath supercontinents. The Jurassic break-up of the Central Atlantic and the Cretaceous rifting that formed the South Atlantic Ocean are both associated with excess temperatures of ˜ 50 °C that have e-folding times of ˜ 50 Ma. In addition to this background trend, excess temperatures reach > 150 °C around the region of the Rio Grande Rise, associated with the present-day Tristan hotspot. The e-folding time of this more local event is ˜ 10 Ma, which mirrors results obtained for the North Atlantic Ocean south of Iceland. In contrast, crustal thicknesses from the Pacific Ocean reveal approximately constant potential temperature through time. This observation is in agreement with predictions, as the western Pacific was formed by rifting of an oceanic plate. In summary

Precise monitoring of global temperature trends from satellites

NASA Technical Reports Server (NTRS)

Spencer, Roy W.; Christy, John R.

1990-01-01

Passive microwave radiometry from satellites provides more precise atmospheric temperature information than that obtained from the relatively sparse distribution of thermometers over the earth's surface. Accurate global atmospheric temperature estimates are needed for detection of possible greenhouse warming, evaluation of computer models of climate change, and for understanding important factors in the climate system. Analysis of the first 10 years (1979 to 1988) of satellite measurements of lower atmospheric temperature changes reveals a monthly precision of 0.01 C, large temperature variability on time scales from weeks to several years, but no obvious trend for the 10-year period. The warmest years, in descending order, were 1987, 1988, 1983, and 1980. The years 1984, 1985, and 1986 were the coolest.

Reconciling divergent trends and millennial variations in Holocene temperatures.

PubMed

Marsicek, Jeremiah; Shuman, Bryan N; Bartlein, Patrick J; Shafer, Sarah L; Brewer, Simon

2018-01-31

Cooling during most of the past two millennia has been widely recognized and has been inferred to be the dominant global temperature trend of the past 11,700 years (the Holocene epoch). However, long-term cooling has been difficult to reconcile with global forcing, and climate models consistently simulate long-term warming. The divergence between simulations and reconstructions emerges primarily for northern mid-latitudes, for which pronounced cooling has been inferred from marine and coastal records using multiple approaches. Here we show that temperatures reconstructed from sub-fossil pollen from 642 sites across North America and Europe closely match simulations, and that long-term warming, not cooling, defined the Holocene until around 2,000 years ago. The reconstructions indicate that evidence of long-term cooling was limited to North Atlantic records. Early Holocene temperatures on the continents were more than two degrees Celsius below those of the past two millennia, consistent with the simulated effects of remnant ice sheets in the climate model Community Climate System Model 3 (CCSM3). CCSM3 simulates increases in 'growing degree days'-a measure of the accumulated warmth above five degrees Celsius per year-of more than 300 kelvin days over the Holocene, consistent with inferences from the pollen data. It also simulates a decrease in mean summer temperatures of more than two degrees Celsius, which correlates with reconstructed marine trends and highlights the potential importance of the different subseasonal sensitivities of the records. Despite the differing trends, pollen- and marine-based reconstructions are correlated at millennial-to-centennial scales, probably in response to ice-sheet and meltwater dynamics, and to stochastic dynamics similar to the temperature variations produced by CCSM3. Although our results depend on a single source of palaeoclimatic data (pollen) and a single climate-model simulation, they reinforce the notion that climate

Reconciling divergent trends and millennial variations in Holocene temperatures

NASA Astrophysics Data System (ADS)

Marsicek, Jeremiah; Shuman, Bryan N.; Bartlein, Patrick J.; Shafer, Sarah L.; Brewer, Simon

2018-02-01

Cooling during most of the past two millennia has been widely recognized and has been inferred to be the dominant global temperature trend of the past 11,700 years (the Holocene epoch). However, long-term cooling has been difficult to reconcile with global forcing, and climate models consistently simulate long-term warming. The divergence between simulations and reconstructions emerges primarily for northern mid-latitudes, for which pronounced cooling has been inferred from marine and coastal records using multiple approaches. Here we show that temperatures reconstructed from sub-fossil pollen from 642 sites across North America and Europe closely match simulations, and that long-term warming, not cooling, defined the Holocene until around 2,000 years ago. The reconstructions indicate that evidence of long-term cooling was limited to North Atlantic records. Early Holocene temperatures on the continents were more than two degrees Celsius below those of the past two millennia, consistent with the simulated effects of remnant ice sheets in the climate model Community Climate System Model 3 (CCSM3). CCSM3 simulates increases in ‘growing degree days’—a measure of the accumulated warmth above five degrees Celsius per year—of more than 300 kelvin days over the Holocene, consistent with inferences from the pollen data. It also simulates a decrease in mean summer temperatures of more than two degrees Celsius, which correlates with reconstructed marine trends and highlights the potential importance of the different subseasonal sensitivities of the records. Despite the differing trends, pollen- and marine-based reconstructions are correlated at millennial-to-centennial scales, probably in response to ice-sheet and meltwater dynamics, and to stochastic dynamics similar to the temperature variations produced by CCSM3. Although our results depend on a single source of palaeoclimatic data (pollen) and a single climate-model simulation, they reinforce the notion that

Trend analysis of long-term temperature time series in the Greater Toronto Area (GTA)

NASA Astrophysics Data System (ADS)

Mohsin, Tanzina; Gough, William A.

2010-08-01

As the majority of the world’s population is living in urban environments, there is growing interest in studying local urban climates. In this paper, for the first time, the long-term trends (31-162 years) of temperature change have been analyzed for the Greater Toronto Area (GTA). Annual and seasonal time series for a number of urban, suburban, and rural weather stations are considered. Non-parametric statistical techniques such as Mann-Kendall test and Theil-Sen slope estimation are used primarily for the assessing of the significance and detection of trends, and the sequential Mann test is used to detect any abrupt climate change. Statistically significant trends for annual mean and minimum temperatures are detected for almost all stations in the GTA. Winter is found to be the most coherent season contributing substantially to the increase in annual minimum temperature. The analyses of the abrupt changes in temperature suggest that the beginning of the increasing trend in Toronto started after the 1920s and then continued to increase to the 1960s. For all stations, there is a significant increase of annual and seasonal (particularly winter) temperatures after the 1980s. In terms of the linkage between urbanization and spatiotemporal thermal patterns, significant linear trends in annual mean and minimum temperature are detected for the period of 1878-1978 for the urban station, Toronto, while for the rural counterparts, the trends are not significant. Also, for all stations in the GTA that are situated in all directions except south of Toronto, substantial temperature change is detected for the periods of 1970-2000 and 1989-2000. It is concluded that the urbanization in the GTA has significantly contributed to the increase of the annual mean temperatures during the past three decades. In addition to urbanization, the influence of local climate, topography, and larger scale warming are incorporated in the analysis of the trends.

Moderate-resolution sea surface temperature data for the Arctic Ocean Ecoregions

EPA Science Inventory

Sea surface temperature (SST) is an important environmental characteristic in determining the suitability and sustainability of habitats for marine organisms. Of particular interest is the fate of the Arctic Ocean, which provides critical habitat to commercially important fish (M...

Precipitation and temperature trends over central Italy (Abruzzo Region): 1951-2012

NASA Astrophysics Data System (ADS)

Scorzini, Anna Rita; Leopardi, Maurizio

2018-02-01

This study analyses spatial and temporal trends of precipitation and temperatures over Abruzzo Region (central Italy), using historical climatic data from a dense observation network. The results show a general, although not significant, negative trend in the regionally averaged annual precipitation (- 1.8% of the yearly mean rainfall per decade). This reduction is particularly evident in winter, especially at mountain stations (average - 3% change/decade). Despite this general decreasing trend, a partial rainfall recovery is observed after the 1980s. Furthermore, the majority of meteorological stations register a significant warming over the last 60 years, (mean annual temperature increase of + 0.15 °C/decade), which reflects a rise in both minimum and maximum temperatures, with the latter generally increasing at a faster rate. Spring and summer are the seasons which contribute most to the general temperature increase, in particular at high elevation sites, which exhibit a more pronounced warming (+ 0.24 °C/decade). However, this tendency has not been uniform over 1951-2012, but it has been characterised by a cooling phenomenon in the first 30 years (1951-1981), followed by an even stronger warming during the last three decades (1982-2012). Finally, correlations between the climatic variables and the dominant teleconnection patterns in the Mediterranean basin are analysed to identify the potential influence of large-scale atmospheric dynamics on observed trends in Abruzzo. The results highlight the dominant role of the East-Atlantic pattern on seasonal temperatures, while more spatially heterogeneous associations, depending on the complex topography of the region, are identified between winter precipitation and the North Atlantic Oscillation, East-Atlantic and East-Atlantic/Western Russian patterns.

An 'Observational Large Ensemble' to compare observed and modeled temperature trend uncertainty due to internal variability.

NASA Astrophysics Data System (ADS)

Poppick, A. N.; McKinnon, K. A.; Dunn-Sigouin, E.; Deser, C.

2017-12-01

Initial condition climate model ensembles suggest that regional temperature trends can be highly variable on decadal timescales due to characteristics of internal climate variability. Accounting for trend uncertainty due to internal variability is therefore necessary to contextualize recent observed temperature changes. However, while the variability of trends in a climate model ensemble can be evaluated directly (as the spread across ensemble members), internal variability simulated by a climate model may be inconsistent with observations. Observation-based methods for assessing the role of internal variability on trend uncertainty are therefore required. Here, we use a statistical resampling approach to assess trend uncertainty due to internal variability in historical 50-year (1966-2015) winter near-surface air temperature trends over North America. We compare this estimate of trend uncertainty to simulated trend variability in the NCAR CESM1 Large Ensemble (LENS), finding that uncertainty in wintertime temperature trends over North America due to internal variability is largely overestimated by CESM1, on average by a factor of 32%. Our observation-based resampling approach is combined with the forced signal from LENS to produce an 'Observational Large Ensemble' (OLENS). The members of OLENS indicate a range of spatially coherent fields of temperature trends resulting from different sequences of internal variability consistent with observations. The smaller trend variability in OLENS suggests that uncertainty in the historical climate change signal in observations due to internal variability is less than suggested by LENS.

Climate, carbon cycling, and deep-ocean ecosystems.

PubMed

Smith, K L; Ruhl, H A; Bett, B J; Billett, D S M; Lampitt, R S; Kaufmann, R S

2009-11-17

Climate variation affects surface ocean processes and the production of organic carbon, which ultimately comprises the primary food supply to the deep-sea ecosystems that occupy approximately 60% of the Earth's surface. Warming trends in atmospheric and upper ocean temperatures, attributed to anthropogenic influence, have occurred over the past four decades. Changes in upper ocean temperature influence stratification and can affect the availability of nutrients for phytoplankton production. Global warming has been predicted to intensify stratification and reduce vertical mixing. Research also suggests that such reduced mixing will enhance variability in primary production and carbon export flux to the deep sea. The dependence of deep-sea communities on surface water production has raised important questions about how climate change will affect carbon cycling and deep-ocean ecosystem function. Recently, unprecedented time-series studies conducted over the past two decades in the North Pacific and the North Atlantic at >4,000-m depth have revealed unexpectedly large changes in deep-ocean ecosystems significantly correlated to climate-driven changes in the surface ocean that can impact the global carbon cycle. Climate-driven variation affects oceanic communities from surface waters to the much-overlooked deep sea and will have impacts on the global carbon cycle. Data from these two widely separated areas of the deep ocean provide compelling evidence that changes in climate can readily influence deep-sea processes. However, the limited geographic coverage of these existing time-series studies stresses the importance of developing a more global effort to monitor deep-sea ecosystems under modern conditions of rapidly changing climate.

Observation of local cloud and moisture feedbacks over high ocean and desert surface temperatures

NASA Technical Reports Server (NTRS)

Chahine, Moustafa T.

1995-01-01

New data on clouds and moisture, made possible by reanalysis of weather satellite observations, show that the atmosphere reacts to warm clusters of very high sea surface temperatures in the western Pacific Ocean with increased moisture, cloudiness, and convection, suggesting a negative feedback limiting the sea surface temperature rise. The reverse was observed over dry and hot deserts where both moisture and cloudiness decrease, suggesting a positive feedback perpetuating existing desert conditions. In addition, the observations show a common critical surface temperature for both oceans and land; the distribution of atmospheric moisture is observed to reach a maximum value when the daily surface temperatures approach 304 +/- 1 K. These observations reveal complex dynamic-radiative interactions where multiple processes act simultaneously at the surface as well as in the atmosphere to regulate the feedback processes.

Trend analysis of tropical intraseasonal oscillations in the summer and winter during 1982-2009

NASA Astrophysics Data System (ADS)

Tao, Li; Zhao, Jiuwei; Li, Tim

2015-04-01

Based on the daily outgoing long-wave radiation (OLR) data of the National Oceanic and Atmospheric Administration (NOAA) from 1979 to 2012, we investigated the intensity changes of the 20-70-d boreal summer (June-September; JJAS) intra-seasonal oscillation (BSISO) and winter (December-February; DJF) intra-seasonal oscillation, also known as the Madden-Julian Oscillation (MJO). The results showed that the intensity of the BSISO has a significant intensifying trend during 1982-2009. On the other hand, little trend was found for boreal winter MJO during this period. The wavenumber-frequency analysis (Hayashi, 1982) was applied to separate ISO into westward propagation and eastward propagation parts. The significant intensified trend was observed over tropical Indian Ocean for the eastward-propagation BSISO. The weakened but not significant trend was observed over southern tropical Indian Ocean for the eastward-propagation MJO. To gain insight into the different ISO characteristics, the tendencies of sea surface temperature (SST) and the vertical shear of zonal wind were analyzed. The results showed that in both seasons from 1982 to 2009, the global SST trends were similar, and thus they could not be used to explain the BSISO upward trend. However, lower-tropospheric easterly shear in boreal summer over tropical Indian Ocean has a decreasing trend, while the easterly vertical shear over maritime continent was enhanced in winter. It is proposed that the reduced easterly vertical shear over tropical Indian Ocean favored the amplification of the eastward-propagating Kelvin wave, which led to the intensified eastward-propagating BSISO. The enhanced easterly vertical shear over maritime continent might be unfavorable to the amplification of the eastward-propagating Kelvin wave, but its impact was offset by the enhanced upward motion over maritime continent. As a result, there was little trend of the MJO in boreal winter. The hypothesis above was further verified by

Twentieth century bipolar seesaw of the Arctic and Antarctic surface air temperatures

NASA Astrophysics Data System (ADS)

Chylek, Petr; Folland, Chris K.; Lesins, Glen; Dubey, Manvendra K.

2010-04-01

Understanding the phase relationship between climate changes in the Arctic and Antarctic regions is essential for our understanding of the dynamics of the Earth's climate system. In this paper we show that the 20th century de-trended Arctic and Antarctic temperatures vary in anti-phase seesaw pattern - when the Arctic warms the Antarctica cools and visa versa. This is the first time that a bi-polar seesaw pattern has been identified in the 20th century Arctic and Antarctic temperature records. The Arctic (Antarctic) de-trended temperatures are highly correlated (anti-correlated) with the Atlantic Multi-decadal Oscillation (AMO) index suggesting the Atlantic Ocean as a possible link between the climate variability of the Arctic and Antarctic regions. Recent accelerated warming of the Arctic results from a positive reinforcement of the linear warming trend (due to an increasing concentration of greenhouse gases and other possible forcings) by the warming phase of the multidecadal climate variability (due to fluctuations of the Atlantic Ocean circulation).

Temperature Data Assimilation with Salinity Corrections: Validation for the NSIPP Ocean Data Assimilation System in the Tropical Pacific Ocean, 1993-1998

NASA Technical Reports Server (NTRS)

Troccoli, Alberto; Rienecker, Michele M.; Keppenne, Christian L.; Johnson, Gregory C.

2003-01-01

The NASA Seasonal-to-Interannual Prediction Project (NSIPP) has developed an Ocean data assimilation system to initialize the quasi-isopycnal ocean model used in our experimental coupled-model forecast system. Initial tests of the system have focused on the assimilation of temperature profiles in an optimal interpolation framework. It is now recognized that correction of temperature only often introduces spurious water masses. The resulting density distribution can be statically unstable and also have a detrimental impact on the velocity distribution. Several simple schemes have been developed to try to correct these deficiencies. Here the salinity field is corrected by using a scheme which assumes that the temperature-salinity relationship of the model background is preserved during the assimilation. The scheme was first introduced for a zlevel model by Troccoli and Haines (1999). A large set of subsurface observations of salinity and temperature is used to cross-validate two data assimilation experiments run for the 6-year period 1993-1998. In these two experiments only subsurface temperature observations are used, but in one case the salinity field is also updated whenever temperature observations are available.

Indian Ocean corals reveal crucial role of World War II bias for twentieth century warming estimates.

PubMed

Pfeiffer, M; Zinke, J; Dullo, W-C; Garbe-Schönberg, D; Latif, M; Weber, M E

2017-10-31

The western Indian Ocean has been warming faster than any other tropical ocean during the 20 th century, and is the largest contributor to the global mean sea surface temperature (SST) rise. However, the temporal pattern of Indian Ocean warming is poorly constrained and depends on the historical SST product. As all SST products are derived from the International Comprehensive Ocean-Atmosphere dataset (ICOADS), it is challenging to evaluate which product is superior. Here, we present a new, independent SST reconstruction from a set of Porites coral geochemical records from the western Indian Ocean. Our coral reconstruction shows that the World War II bias in the historical sea surface temperature record is the main reason for the differences between the SST products, and affects western Indian Ocean and global mean temperature trends. The 20 th century Indian Ocean warming pattern portrayed by the corals is consistent with the SST product from the Hadley Centre (HadSST3), and suggests that the latter should be used in climate studies that include Indian Ocean SSTs. Our data shows that multi-core coral temperature reconstructions help to evaluate the SST products. Proxy records can provide estimates of 20 th century SST that are truly independent from the ICOADS data base.

Trends in Upper-Level Cloud Cover and Surface Divergence Over the Tropical Indo-Pacific Ocean Between 1952 And 1997

NASA Technical Reports Server (NTRS)

Norris, Joel R.

2005-01-01

This study investigated the spatial pattern of linear trends in surface-observed upper-level (combined mid-level and High-level) cloud cover, precipitation, and surface divergence over the tropical Indo-Pacific Ocean during 1952-1957. Cloud values were obtained from the Extended Edited Cloud Report Archive (EECRA), precipitation values were obtained from the Hulme/Climate Research Unit Data Set, and surface divergence was alternatively calculated from wind reported Comprehensive Ocean-Atmosphere Data Set and from Smith and Reynolds Extended Reconstructed sea level pressure data.

Ocean chemistry controls trends in foraminiferal mineralogy

NASA Astrophysics Data System (ADS)

de Nooijer, Lennart; van Dijk, Inge; Reichart, Gert-Jan

2014-05-01

Foraminifera are unicellular marine protists of which many produce a calcium carbonate shell of either aragonite or calcite. Since they are responsible for a large part of open ocean calcium carbonate precipitation, it is necessary to understand their response to changes in ocean chemistry. On geological time scales, the ratio of Mg over Ca in seawater played an important role in controlling marine aragonite versus calcite mineralogy. Here we reconstructed occurrences of aragonite and low- and high-Mg calcite producing foraminifera through the Phanerozoic. We discovered a two-step impact of seawater chemistry and mass extinction events on the evolution of foraminifera. Seawater Mg to Ca ratios favor production of either calcite, or of high magnesium carbonate and aragonite shells. However, mass extinction events controlled the timing of shifts in dominance from one mineralogy to the other. This observation suggests that ongoing ocean acidification may have important consequences for foraminiferal calcification. Although reduced carbonate saturation state increases dissolution rates of high-Mg calcite and aragonite compared to low-Mg calcite, the current high Mg/Ca of the ocean kinetically favors precipitation of high-Mg calcite and aragonite. Contrary to the differential effects of dissolution, we argue that ongoing ocean acidification is likely to particularly impact calcite producers (e.g. planktonic foraminifera, coccolithophores) compared to those precipitating high-Mg calcite and aragonite (e.g. corals).

Depth perception: the need to report ocean biogeochemical rates as functions of temperature, not depth

NASA Astrophysics Data System (ADS)

Brewer, Peter G.; Peltzer, Edward T.

2017-08-01

For over 50 years, ocean scientists have oddly represented ocean oxygen consumption rates as a function of depth but not temperature in most biogeochemical models. This unique tradition or tactic inhibits useful discussion of climate change impacts, where specific and fundamental temperature-dependent terms are required. Tracer-based determinations of oxygen consumption rates in the deep sea are nearly universally reported as a function of depth in spite of their well-known microbial basis. In recent work, we have shown that a carefully determined profile of oxygen consumption rates in the Sargasso Sea can be well represented by a classical Arrhenius function with an activation energy of 86.5 kJ mol-1, leading to a Q10 of 3.63. This indicates that for 2°C warming, we will have a 29% increase in ocean oxygen consumption rates, and for 3°C warming, a 47% increase, potentially leading to large-scale ocean hypoxia should a sufficient amount of organic matter be available to microbes. Here, we show that the same principles apply to a worldwide collation of tracer-based oxygen consumption rate data and that some 95% of ocean oxygen consumption is driven by temperature, not depth, and thus will have a strong climate dependence. The Arrhenius/Eyring equations are no simple panacea and they require a non-equilibrium steady state to exist. Where transient events are in progress, this stricture is not obeyed and we show one such possible example. This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'.

Trend analysis and change point detection of annual and seasonal temperature series in Peninsular Malaysia

NASA Astrophysics Data System (ADS)

Suhaila, Jamaludin; Yusop, Zulkifli

2017-06-01

Most of the trend analysis that has been conducted has not considered the existence of a change point in the time series analysis. If these occurred, then the trend analysis will not be able to detect an obvious increasing or decreasing trend over certain parts of the time series. Furthermore, the lack of discussion on the possible factors that influenced either the decreasing or the increasing trend in the series needs to be addressed in any trend analysis. Hence, this study proposes to investigate the trends, and change point detection of mean, maximum and minimum temperature series, both annually and seasonally in Peninsular Malaysia and determine the possible factors that could contribute to the significance trends. In this study, Pettitt and sequential Mann-Kendall (SQ-MK) tests were used to examine the occurrence of any abrupt climate changes in the independent series. The analyses of the abrupt changes in temperature series suggested that most of the change points in Peninsular Malaysia were detected during the years 1996, 1997 and 1998. These detection points captured by Pettitt and SQ-MK tests are possibly related to climatic factors, such as El Niño and La Niña events. The findings also showed that the majority of the significant change points that exist in the series are related to the significant trend of the stations. Significant increasing trends of annual and seasonal mean, maximum and minimum temperatures in Peninsular Malaysia were found with a range of 2-5 °C/100 years during the last 32 years. It was observed that the magnitudes of the increasing trend in minimum temperatures were larger than the maximum temperatures for most of the studied stations, particularly at the urban stations. These increases are suspected to be linked with the effect of urban heat island other than El Niño event.

The paradox of cooling streams in a warming world: Regional climate trends do not parallel variable local trends in stream temperature in the Pacific continental United States

USGS Publications Warehouse

Arismendi, Ivan; Johnson, Sherri; Dunham, Jason B.; Haggerty, Roy; Hockman-Wert, David

2012-01-01

Temperature is a fundamentally important driver of ecosystem processes in streams. Recent warming of terrestrial climates around the globe has motivated concern about consequent increases in stream temperature. More specifically, observed trends of increasing air temperature and declining stream flow are widely believed to result in corresponding increases in stream temperature. Here, we examined the evidence for this using long-term stream temperature data from minimally and highly human-impacted sites located across the Pacific continental United States. Based on hypothesized climate impacts, we predicted that we should find warming trends in the maximum, mean and minimum temperatures, as well as increasing variability over time. These predictions were not fully realized. Warming trends were most prevalent in a small subset of locations with longer time series beginning in the 1950s. More recent series of observations (1987-2009) exhibited fewer warming trends and more cooling trends in both minimally and highly human-influenced systems. Trends in variability were much less evident, regardless of the length of time series. Based on these findings, we conclude that our perspective of climate impacts on stream temperatures is clouded considerably by a lack of long-termdata on minimally impacted streams, and biased spatio-temporal representation of existing time series. Overall our results highlight the need to develop more mechanistic, process-based understanding of linkages between climate change, other human impacts and stream temperature, and to deploy sensor networks that will provide better information on trends in stream temperatures in the future.

Decadal Variability and Temperature Trends in the Middle Atmosphere From Historical Rocketsonde Data

NASA Technical Reports Server (NTRS)

Dunkerton, Timothy J.

2000-01-01

Observational studies were performed using historical rocketsonde data to investigate long-term temperature trends, solar-cycle variations, and interactions between tropical and extratropical latitudes in the middle atmosphere. Evidence from tropical, subtropical, and midlatitude North American rocketsonde stations indicated a consistent downward trend over 25 years, with a solar cycle component superposed. The trend is about -1.4 to -2.0 K per decade and the amplitude of the decadal oscillation is about 1.1 K. Prior to trend derivation it was necessary for us to correct temperatures for aerodynamic heating in the early years. The empirically derived correction profile agrees well with a theoretical profile of Krumins and Lyons. A study was also performed of the correlation between equatorial winds and north polar temperatures in winter, showing that the entire stratospheric wind profile near the equator -- including the quasi-biennial oscillation (QBO) and stratopause semiannual oscillation (SAO) -- is important to the extratropical flow, not merely the QBO component as previously thought. A strong correlation was discovered between winter polar temperatures and equatorial winds in the upper stratosphere during the preceding September, suggesting a role for the second cycle of the SAO.

Investigation of land ice-ocean interaction with a fully coupled ice-ocean model: 1. Model description and behavior

NASA Astrophysics Data System (ADS)

Goldberg, D. N.; Little, C. M.; Sergienko, O. V.; Gnanadesikan, A.; Hallberg, R.; Oppenheimer, M.

2012-06-01

Antarctic ice shelves interact closely with the ocean cavities beneath them, with ice shelf geometry influencing ocean cavity circulation, and heat from the ocean driving changes in the ice shelves, as well as the grounded ice streams that feed them. We present a new coupled model of an ice stream-ice shelf-ocean system that is used to study this interaction. The model is capable of representing a moving grounding line and dynamically responding ocean circulation within the ice shelf cavity. Idealized experiments designed to investigate the response of the coupled system to instantaneous increases in ocean temperature show ice-ocean system responses on multiple timescales. Melt rates and ice shelf basal slopes near the grounding line adjust in 1-2 years, and downstream advection of the resulting ice shelf thinning takes place on decadal timescales. Retreat of the grounding line and adjustment of grounded ice takes place on a much longer timescale, and the system takes several centuries to reach a new steady state. During this slow retreat, and in the absence of either an upward-or downward-sloping bed or long-term trends in ocean heat content, the ice shelf and melt rates maintain a characteristic pattern relative to the grounding line.

Relationships between ten-year trends of tropospheric ozone and temperature over Taiwan.

PubMed

Hsu, Kuang-Jung

2007-03-01

The analyses of ten-year ozonesonde observations from 1993 till 2002, over Taipei, Taiwan show influences of climate change. Despite huge increases in its precursor emissions in this region, there were little variations in tropospheric ozone. Results indicate a warmer troposphere, a statistically insignificant rising tropopause, 79+/-206 m per decade, and decreasing tropopause temperature at -1.0+/-0.89 K per decade. The derived mean tropospheric ozone is 40.58+/-10.99 DU, and has a statistically insignificant small trend of -0.78+/-1.7 DU per decade. The derived ten-year vertical trends of temperature and ozone are inversely correlated with each other from the middle troposphere up to the lower stratosphere. The averaged monthly vertical temperature trends show a generally warmer middle troposphere. The tropospheric ozone monthly trend has small increases only in the lower troposphere during winter and spring. Strong decreases occur in summer, from the surface up into the stratosphere. For ozone variation, results suggest that influences of climate forcing are stronger than those from precursor increases. More frequent and/or intense convection in summer and other climate-induced effects may contribute to the less than expected ozone observed in the troposphere.

Ocean warming since 1982 has expanded the niche of toxic algal blooms in the North Atlantic and North Pacific oceans.

PubMed

Gobler, Christopher J; Doherty, Owen M; Hattenrath-Lehmann, Theresa K; Griffith, Andrew W; Kang, Yoonja; Litaker, R Wayne

2017-05-09

Global ocean temperatures are rising, yet the impacts of such changes on harmful algal blooms (HABs) are not fully understood. Here we used high-resolution sea-surface temperature records (1982 to 2016) and temperature-dependent growth rates of two algae that produce potent biotoxins, Alexandrium fundyense and Dinophysis acuminata , to evaluate recent changes in these HABs. For both species, potential mean annual growth rates and duration of bloom seasons significantly increased within many coastal Atlantic regions between 40°N and 60°N, where incidents of these HABs have emerged and expanded in recent decades. Widespread trends were less evident across the North Pacific, although regions were identified across the Salish Sea and along the Alaskan coastline where blooms have recently emerged, and there have been significant increases in the potential growth rates and duration of these HAB events. We conclude that increasing ocean temperature is an important factor facilitating the intensification of these, and likely other, HABs and thus contributes to an expanding human health threat.

Ocean warming since 1982 has expanded the niche of toxic algal blooms in the North Atlantic and North Pacific oceans

PubMed Central

Gobler, Christopher J.; Doherty, Owen M.; Hattenrath-Lehmann, Theresa K.; Griffith, Andrew W.; Kang, Yoonja; Litaker, R. Wayne

2017-01-01

Global ocean temperatures are rising, yet the impacts of such changes on harmful algal blooms (HABs) are not fully understood. Here we used high-resolution sea-surface temperature records (1982 to 2016) and temperature-dependent growth rates of two algae that produce potent biotoxins, Alexandrium fundyense and Dinophysis acuminata, to evaluate recent changes in these HABs. For both species, potential mean annual growth rates and duration of bloom seasons significantly increased within many coastal Atlantic regions between 40°N and 60°N, where incidents of these HABs have emerged and expanded in recent decades. Widespread trends were less evident across the North Pacific, although regions were identified across the Salish Sea and along the Alaskan coastline where blooms have recently emerged, and there have been significant increases in the potential growth rates and duration of these HAB events. We conclude that increasing ocean temperature is an important factor facilitating the intensification of these, and likely other, HABs and thus contributes to an expanding human health threat. PMID:28439007

Estimating the Mean Annual Surface Air Temperature at Armagh Observatory, Northern Ireland, and the Global Land-Ocean Temperature Index for Sunspot Cycle 24, the Current Ongoing Sunspot Cycle

NASA Technical Reports Server (NTRS)

Wilson, Robert M.

2013-01-01

As noted by Gray et al., Sir William Herschel was the first to suggest a possible close connection between the Sun and the Earth’s climate. The Sun, being the source of energy that impacts and drives the Earth’s climate system, displays a variety of changes over both short and long term time scales, the most obvious examples being the somewhat regular waxing and waning of sunspots with time (i.e., the sunspot cycle (SC)), first described by Samuel Heinrich Schwabe, a German apothecary and amateur astronomer who observed the Sun from Dessau, Germany, and the now well established variation of the Sun’s irradiance over the SC. Other factors related to the SC have been linked to changes in climate as well. Some of these other factors include the role of cosmic rays and the solar wind (i.e., the geomagnetic cycle) on climate, as well as the apparent close association between trends in global and northern hemispheric temperature and the length of the SC, although some investigators have described the inferred association between climate and, in particular, SC length as now being weak. More recently, Solheim et al. have reported on the relation between SC length and the average temperature in the same and immediately following SC for a number of meteorological stations in Norway and in the North Atlantic region. They noted that while they found no significant trend (correlation) between SC length and the average temperature when measured for the same cycle, in contrast, they found a significant negative trend when SC length was compared with the following cycle’s average temperature. From this observation, they suggested that average northern hemispheric temperature during the present ongoing SC (SC24) will be lower by about 0.9 °C than was seen in SC23 (spanning 1996–2007, based on yearly averages of sunspot number (SSN), and onset for SC24 occurring in 2008). The purpose of this Technical Publication (TP) is to examine the annual variations of the Armagh

Analysis of near-shore sea surface temperatures in the Northern Pacific

EPA Science Inventory

Recent studies report a warming trend in Pacific Ocean temperatures over the last 50 years. However, much less is known about temperature change in the near-coastal environment, which is particularly sensitive to climatic change. In near-shore regions in situ sea surface temper...

Understanding Arctic surface temperature differences in reanalyses

NASA Astrophysics Data System (ADS)

Cullather, R. I.; Zhao, B.; Shuman, C. A.; Nowicki, S.

2017-12-01

Reanalyses in the Arctic are widely used for model evaluation and for understanding contemporary climate change. Nevertheless, differences among reanalyses in fundamental meteorological variables including surface air temperature are large. For example, the 1980-2009 mean surface air temperature for the north polar cap (70°N-90°N) among global reanalyses span a range of 2.4 K, which approximates the average warming trend from these reanalyses over the 30-year period of 2.1 K. Understanding these differences requires evaluation over the three principal surface domains of the Arctic: glaciated land, the unglaciated terrestrial surface, and sea ice/ocean. An examination is conducted of contemporary global reanalyses of the ECMWF Interim project, NASA MERRA, MERRA-2, JRA-55, and NOAA CFSR using available in situ data and assessments of the surface energy budget. Overly-simplistic representations of the Greenland Ice Sheet surface are found to be associated with local warm air temperature biases in winter. A review of progress made in the development of the MERRA-2 land-ice representation is presented. Large uncertainty is also found in temperatures over the Arctic tundra and boreal forest zone. But a key focus of temperature differences for northern high latitudes is the Arctic Ocean. Near-surface air temperature differences over the Arctic Ocean are found to be related to discrepancies in sea ice and sea surface temperature boundary data, which are severely compromised in current reanalyses. Issues with the modeled representation of sea ice cover are an additional factor in reanalysis temperature trends. Differences in the representation of the surface energy budget among the various reanalyses are also reviewed.

Understanding Arctic Surface Temperature Differences in Reanalyses

NASA Technical Reports Server (NTRS)

Cullather, Richard; Zhao, Bin; Shuman, Christopher; Nowicki, Sophie

2017-01-01

Reanalyses in the Arctic are widely used for model evaluation and for understanding contemporary climate change. Nevertheless, differences among reanalyses in fundamental meteorological variables including surface air temperature are large. For example, the 1980-2009 mean surface air temperature for the north polar cap (70ÂdegN-90ÂdegN) among global reanalyses span a range of 2.4 K, which approximates the average warming trend from these reanalyses over the 30-year period of 2.1 K. Understanding these differences requires evaluation over the three principal surface domains of the Arctic: glaciated land, the unglaciated terrestrial surface, and sea ice/ocean. An examination is conducted of contemporary global reanalyses of the ECMWF Interim project, NASA MERRA, MERRA-2, JRA-55, and NOAA CFSR using available in situ data and assessments of the surface energy budget. Overly-simplistic representations of the Greenland Ice Sheet surface are found to be associated with local warm air temperature biases in winter. A review of progress made in the development of the MERRA-2 land-ice representation is presented. Large uncertainty is also found in temperatures over the Arctic tundra and boreal forest zone. But a key focus of temperature differences for northern high latitudes is the Arctic Ocean. Near-surface air temperature differences over the Arctic Ocean are found to be related to discrepancies in sea ice and sea surface temperature boundary data, which are severely compromised in current reanalyses. Issues with the modeled representation of sea ice cover are an additional factor in reanalysis temperature trends. Differences in the representation of the surface energy budget among the various reanalyses are also reviewed.

Sulfur geochemistry and microbial sulfate reduction during low-temperature alteration of uplifted lower oceanic crust: Insights from ODP Hole 735B

USGS Publications Warehouse

Alford, Susan E.; Alt, Jeffrey C.; Shanks, Wayne C.

2011-01-01

Sulfide petrography plus whole rock contents and isotope ratios of sulfur were measured in a 1.5 km section of oceanic gabbros in order to understand the geochemistry of sulfur cycling during low-temperature seawater alteration of the lower oceanic crust, and to test whether microbial effects may be present. Most samples have low SO4/ΣS values (≤ 0.15), have retained igneous globules of pyrrhotite ± chalcopyrite ± pentlandite, and host secondary aggregates of pyrrhotite and pyrite laths in smectite ± iron-oxyhydroxide ± magnetite ± calcite pseudomorphs of olivine and clinopyroxene. Compared to fresh gabbro containing 100–1800 ppm sulfur our data indicate an overall addition of sulfide to the lower crust. Selection of samples altered only at temperatures ≤ 110 °C constrains microbial sulfate reduction as the only viable mechanism for the observed sulfide addition, which may have been enabled by the production of H2 from oxidation of associated olivine and pyroxene. The wide range in δ34Ssulfide values (− 1.5 to + 16.3‰) and variable additions of sulfide are explained by variable εsulfate-sulfide under open system pathways, with a possible progression into closed system pathways. Some samples underwent oxidation related to seawater penetration along permeable fault horizons and have lost sulfur, have high SO4/ΣS (≥ 0.46) and variable δ34Ssulfide (0.7 to 16.9‰). Negative δ34Ssulfate–δ34Ssulfide values for the majority of samples indicate kinetic isotope fractionation during oxidation of sulfide minerals. Depth trends in sulfide–sulfur contents and sulfide mineral assemblages indicate a late-stage downward penetration of seawater into the lower 1 km of Hole 735B. Our results show that under appropriate temperature conditions, a subsurface biosphere can persist in the lower oceanic crust and alter its geochemistry.

The response of grounded ice to ocean temperature forcing in a coupled ice sheet-ice shelf-ocean cavity model

NASA Astrophysics Data System (ADS)

Goldberg, D. N.; Little, C. M.; Sergienko, O. V.; Gnanadesikan, A.

2010-12-01

Ice shelves provide a pathway for the heat content of the ocean to influence continental ice sheets. Changes in the rate or location of basal melting can alter their geometry and effect changes in stress conditions at the grounding line, leading to a grounded ice response. Recent observations of ice streams and ice shelves in the Amundsen Sea sector of West Antarctica have been consistent with this story. On the other hand, ice dynamics in the grounding zone control flux into the shelf and thus ice shelf geometry, which has a strong influence on the circulation in the cavity beneath the shelf. Thus the coupling between the two systems, ocean and ice sheet-ice shelf, can be quite strong. We examine the response of the ice sheet-ice shelf-ocean cavity system to changes in ocean temperature using a recently developed coupled model. The coupled model consists a 3-D ocean model (GFDL's Generalized Ocean Layered Dynamics model, or GOLD) to a two-dimensional ice sheet-ice shelf model (Goldberg et al, 2009), and allows for changing cavity geometry and a migrating grounding line. Steady states of the coupled system are found even under considerable forcing. The ice shelf morphology and basal melt rate patterns of the steady states exhibit detailed structure, and furthermore seem to be unique and robust. The relationship between temperature forcing and area-averaged melt rate is influenced by the response of ice shelf morphology to thermal forcing, and is found to be sublinear in the range of forcing considered. However, results suggest that area-averaged melt rate is not the best predictor of overall system response, as grounding line stability depends on local aspects of the basal melt field. Goldberg, D N, D M Holland and C G Schoof, 2009. Grounding line movement and ice shelf buttressing in marine ice sheets, Journal of Geophysical Research-Earth Surfaces, 114, F04026.

Detection of temperature trends within the course of the year using "shifting subseasons"

NASA Astrophysics Data System (ADS)

Cahynova, Monika; Pokorna, Lucie

2015-04-01

Recent global warming has not been ubiquitous - there are seasons, regions, and time periods with clearly discernible zero or downward air temperature trends. Regions that are not warming or are even cooling - also known as "warming holes" - have been previously detected mainly in autumn in the second half of the 20th century in large parts of North America as well as in Central and Eastern Europe. Daily maximum and minimum temperature (TX and TN, respectively) and daily temperature range (DTR) at 136 stations in Europe during the period 1961-2000 are employed to precisely locate the seasonal and subseasonal trends within the course of the year. Linear trends are calculated for moving "subseasons" of differing lengths (10, 20, 30, 60, and 90 days), each shifted by one day. Cluster analysis of the annual course of "shifting trends" reveals relatively well-defined regions with similar trend behavior. Over most of Europe, the observed warming is greatest in winter, and the highest trend magnitudes are reached by TN in Eastern Europe. Two regions stand out: in Iceland and the Eastern Mediterranean, the trends during the year are weak, positive in summer and mostly negative in winter, reaching statistical significance at only few stations. Significant autumn cooling centered on mid-November was found in Eastern and Southeastern Europe for both TX and TN; in many other regions trends are close to zero in the same period. Other clearly non-warming (or even cooling) periods occur in Western and Central Europe in February, April, and late June. Trends of DTR are largely inconclusive and no general picture can be drawn. Our results suggest that using different time scales, apart from the conventional three-month seasons or common months, is highly desirable for a proper location of trends within the course of the year.

Globally-Gridded Interpolated Night-Time Marine Air Temperatures 1900-2014

NASA Astrophysics Data System (ADS)

Junod, R.; Christy, J. R.

2016-12-01

Over the past century, climate records have pointed to an increase in global near-surface average temperature. Near-surface air temperature over the oceans is a relatively unused parameter in understanding the current state of climate, but is useful as an independent temperature metric over the oceans and serves as a geographical and physical complement to near-surface air temperature over land. Though versions of this dataset exist (i.e. HadMAT1 and HadNMAT2), it has been strongly recommended that various groups generate climate records independently. This University of Alabama in Huntsville (UAH) study began with the construction of monthly night-time marine air temperature (UAHNMAT) values from the early-twentieth century through to the present era. Data from the International Comprehensive Ocean and Atmosphere Data Set (ICOADS) were used to compile a time series of gridded UAHNMAT, (20S-70N). This time series was homogenized to correct for the many biases such as increasing ship height, solar deck heating, etc. The time series of UAHNMAT, once adjusted to a standard reference height, is gridded to 1.25° pentad grid boxes and interpolated using the kriging interpolation technique. This study will present results which quantify the variability and trends and compare to current trends of other related datasets that include HadNMAT2 and sea-surface temperatures (HadISST & ERSSTv4).

Mid-ocean ridges produced thicker crust in the Jurassic than in Recent times

NASA Astrophysics Data System (ADS)

Van Avendonk, H. J.; Harding, J.; Davis, J. K.; Lawver, L. A.

2016-12-01

We present a compilation of published marine seismic refraction data to show that oceanic crust was 1.7 km thicker on average in the mid-Jurassic (170 Ma) than along the present-day mid-ocean ridge system. Plate reconstructions in a fixed hotspot framework show that the thickness of oceanic crust does not correlate with proximity to mantle hotspots, so it is likely that mid-plate volcanism is not the cause of this global trend. We propose that more melt was extracted from the upper mantle beneath mid-ocean ridges in the Jurassic than in recent times. Numerical studies show that temperature increase of 1 degree C in the mantle can lead to approximately 50-70 m thicker crust, so the upper mantle may have cooled 15-20 degrees C/100 Myr since 170 Ma. This average temperature decrease is larger than the secular cooling rate of the Earth's mantle, which is roughly 10 degrees C/100 Myr since the Archean. Apparently, the present-day configuration and dynamics of continental and oceanic plates removes heat more efficiently from the Earth's mantle than in its earlier history. The increase of ocean crustal thickness with plate age is also stronger in the Indian and Atlantic oceans than in the Pacific Ocean basin. This confirms that thermal insulation by the supercontinent Pangaea raised the temperature of the underlying asthenospheric mantle, which in turn led to more magmatic output at the Jurassic mid-ocean ridges of the Indian and Atlantic oceans.

The seasonal response of the Held-Suarez climate model to prescribed ocean temperature anomalies. I - Results of decadal integrations

NASA Technical Reports Server (NTRS)

Phillips, T. J.; Semtner, A. J., Jr.

1984-01-01

Anomalies in ocean surface temperature have been identified as possible causes of variations in the climate of particular seasons or as a source of interannual climatic variability, and attempts have been made to forecast seasonal climate by using ocean temperatures as predictor variables. However, the seasonal atmospheric response to ocean temperature anomalies has not yet been systematically investigated with nonlinear models. The present investigation is concerned with ten-year integrations involving a model of intermediate complexity, the Held-Suarez climate model. The calculations have been performed to investigate the changes in seasonal climate which result from a fixed anomaly imposed on a seasonally varying, global ocean temperature field. Part I of the paper provides a report on the results of these decadal integrations. Attention is given to model properties, the experimental design, and the anomaly experiments.

The Summertime Warming Trends in Surface Water Temperature of the Great Lakes

NASA Astrophysics Data System (ADS)

Sugiyama, N.; Kravtsov, S.; Roebber, P.

2014-12-01

Over the past 30 years, the Laurentian Great Lakes have exhibited summertime warming trends in surface water temperature which were greater than those in surface air temperature of the surrounding land, by as much as an order of magnitude over some of the regions. For the years 1995-2012, Lake Superior exhibited the most dramatic warming trend in July-mean temperature, of 0.27±0.15 deg. C yr-1, based on the NOAA's GLSEA satellite observations. Shallower lakes, such as Lake Erie, exhibited smaller warming trends. In addition, within each lake, the warming was also the greatest in the regions of larger water depth; for example, some regions of Lake Superior deeper than 200m exhibited surface-water July-mean warming trends which exceeded 0.3 deg. C yr-1. We used a three-column lake model based on the one developed by Hostetler and Barnstein (1990) coupled with a two-layer atmospheric energy balance model to explore the physics behind these warming trends. We found that, as suggested by Austin and Colman (2007), the ice-albedo feedback plays an important role in amplifying the overlake warming trends. Our particular emphasis was on the question of whether the ice-albedo feedback alone is enough to account for lacustrine amplification of surface warming observed over the Great Lakes region. We found that the answer to this question depends on a number of model parameters, including the diffusion and light attenuation coefficients, which greatly affect the model's skill in reproducing the observed ice coverage of the deep lakes.

Warming Trends and Bleaching Stress of the World's Coral Reefs 1985-2012.

PubMed

Heron, Scott F; Maynard, Jeffrey A; van Hooidonk, Ruben; Eakin, C Mark

2016-12-06

Coral reefs across the world's oceans are in the midst of the longest bleaching event on record (from 2014 to at least 2016). As many of the world's reefs are remote, there is limited information on how past thermal conditions have influenced reef composition and current stress responses. Using satellite temperature data for 1985-2012, the analysis we present is the first to quantify, for global reef locations, spatial variations in warming trends, thermal stress events and temperature variability at reef-scale (~4 km). Among over 60,000 reef pixels globally, 97% show positive SST trends during the study period with 60% warming significantly. Annual trends exceeded summertime trends at most locations. This indicates that the period of summer-like temperatures has become longer through the record, with a corresponding shortening of the 'winter' reprieve from warm temperatures. The frequency of bleaching-level thermal stress increased three-fold between 1985-91 and 2006-12 - a trend climate model projections suggest will continue. The thermal history data products developed enable needed studies relating thermal history to bleaching resistance and community composition. Such analyses can help identify reefs more resilient to thermal stress.

Retrieving Temperature Anomaly in the Global Subsurface and Deeper Ocean From Satellite Observations

NASA Astrophysics Data System (ADS)

Su, Hua; Li, Wene; Yan, Xiao-Hai

2018-01-01

Retrieving the subsurface and deeper ocean (SDO) dynamic parameters from satellite observations is crucial for effectively understanding ocean interior anomalies and dynamic processes, but it is challenging to accurately estimate the subsurface thermal structure over the global scale from sea surface parameters. This study proposes a new approach based on Random Forest (RF) machine learning to retrieve subsurface temperature anomaly (STA) in the global ocean from multisource satellite observations including sea surface height anomaly (SSHA), sea surface temperature anomaly (SSTA), sea surface salinity anomaly (SSSA), and sea surface wind anomaly (SSWA) via in situ Argo data for RF training and testing. RF machine-learning approach can accurately retrieve the STA in the global ocean from satellite observations of sea surface parameters (SSHA, SSTA, SSSA, SSWA). The Argo STA data were used to validate the accuracy and reliability of the results from the RF model. The results indicated that SSHA, SSTA, SSSA, and SSWA together are useful parameters for detecting SDO thermal information and obtaining accurate STA estimations. The proposed method also outperformed support vector regression (SVR) in global STA estimation. It will be a useful technique for studying SDO thermal variability and its role in global climate system from global-scale satellite observations.

Mangrove expansion and contraction at a poleward range limit: climate extremes and land-ocean temperature gradients.

PubMed

Osland, Michael J; Day, Richard H; Hall, Courtney T; Brumfield, Marisa D; Dugas, Jason L; Jones, William R

2017-01-01

Within the context of climate change, there is a pressing need to better understand the ecological implications of changes in the frequency and intensity of climate extremes. Along subtropical coasts, less frequent and warmer freeze events are expected to permit freeze-sensitive mangrove forests to expand poleward and displace freeze-tolerant salt marshes. Here, our aim was to better understand the drivers of poleward mangrove migration by quantifying spatiotemporal patterns in mangrove range expansion and contraction across land-ocean temperature gradients. Our work was conducted in a freeze-sensitive mangrove-marsh transition zone that spans a land-ocean temperature gradient in one of the world's most wetland-rich regions (Mississippi River Deltaic Plain; Louisiana, USA). We used historical air temperature data (1893-2014), alternative future climate scenarios, and coastal wetland coverage data (1978-2011) to investigate spatiotemporal fluctuations and climate-wetland linkages. Our analyses indicate that changes in mangrove coverage have been controlled primarily by extreme freeze events (i.e., air temperatures below a threshold zone of -6.3 to -7.6°C). We expect that in the past 121 yr, mangrove range expansion and contraction has occurred across land-ocean temperature gradients. Mangrove resistance, resilience, and dominance were all highest in areas closer to the ocean where temperature extremes were buffered by large expanses of water and saturated soil. Under climate change, these areas will likely serve as local hotspots for mangrove dispersal, growth, range expansion, and displacement of salt marsh. Collectively, our results show that the frequency and intensity of freeze events across land-ocean temperature gradients greatly influences spatiotemporal patterns of range expansion and contraction of freeze-sensitive mangroves. We expect that, along subtropical coasts, similar processes govern the distribution and abundance of other freeze

Mangrove expansion and contraction at a poleward range limit: Climate extremes and land-ocean temperature gradients

USGS Publications Warehouse

Osland, Michael J.; Day, Richard H.; Hall, Courtney T.; Brumfield, Marisa D; Dugas, Jason; Jones, William R.

2017-01-01

Within the context of climate change, there is a pressing need to better understand the ecological implications of changes in the frequency and intensity of climate extremes. Along subtropical coasts, less frequent and warmer freeze events are expected to permit freeze-sensitive mangrove forests to expand poleward and displace freeze-tolerant salt marshes. Here, our aim was to better understand the drivers of poleward mangrove migration by quantifying spatiotemporal patterns in mangrove range expansion and contraction across land-ocean temperature gradients. Our work was conducted in a freeze-sensitive mangrove-marsh transition zone that spans a land-ocean temperature gradient in one of the world's most wetland-rich regions (Mississippi River Deltaic Plain; Louisiana, USA). We used historical air temperature data (1893-2014), alternative future climate scenarios, and coastal wetland coverage data (1978-2011) to investigate spatiotemporal fluctuations and climate-wetland linkages. Our analyses indicate that changes in mangrove coverage have been controlled primarily by extreme freeze events (i.e., air temperatures below a threshold zone of -6.3 to -7.6 °C). We expect that in the past 121 years, mangrove range expansion and contraction has occurred across land-ocean temperature gradients. Mangrove resistance, resilience, and dominance were all highest in areas closer to the ocean where temperature extremes were buffered by large expanses of water and saturated soil. Under climate change, these areas will likely serve as local hotspots for mangrove dispersal, growth, range expansion, and displacement of salt marsh. Collectively, our results show that the frequency and intensity of freeze events across land-ocean temperature gradients greatly influences spatiotemporal patterns of range expansion and contraction of freeze-sensitive mangroves. We expect that, along subtropical coasts, similar processes govern the distribution and abundance of other freeze

Tropical Indian Ocean Variability Driving Southeast Australian Droughts

NASA Astrophysics Data System (ADS)

Ummenhofer, C. C.; England, M. H.; McIntosh, P. C.; Meyers, G. A.; Pook, M. J.; Risbey, J. S.; Sen Gupta, A.; Taschetto, A. S.

2009-04-01

Variability in the tropical Indian Ocean has widespread effects on rainfall in surrounding countries, including East Africa, India and Indonesia. The leading mode of tropical Indian Ocean variability, the Indian Ocean Dipole (IOD), is a coupled ocean-atmosphere mode characterized by sea surface temperature (SST) anomalies of opposite sign in the east and west of the basin with an associated large-scale atmospheric re-organisation. Earlier work has often focused on the positive phase of the IOD. However, we show here that the negative IOD phase is an important driver of regional rainfall variability and multi-year droughts. For southeastern Australia, we show that it is actually a lack of the negative IOD phase, rather than the positive IOD phase or Pacific variability, that provides the most robust explanation for recent drought conditions. Since 1995, a large region of Australia has been gripped by the most severe drought in living memory, the so-called "Big Dry". The ramifications for affected regions are dire, with acute water shortages for rural and metropolitan areas, record agricultural losses, the drying-out of two of Australia's major river systems and far-reaching ecosystem damage. Yet the drought's origins have remained elusive. For Southeast Australia, we show that the "Big Dry" and other iconic 20th Century droughts, including the Federation Drought (1895-1902) and World War II drought (1937-1945), are driven by tropical Indian Ocean variability, not Pacific Ocean conditions as traditionally assumed. Specifically, a conspicuous absence of characteristic Indian Ocean temperature conditions that are conducive to enhanced tropical moisture transport has deprived southeastern Australia of its normal rainfall quota. In the case of the "Big Dry", its unprecedented intensity is also related to recent above-average temperatures. Implications of recent non-uniform warming trends in the Indian Ocean and how that might affect ocean characteristics and climate in

Ocean backscatter across the Gulf Stream sea surface temperature front

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nghiem, S.V.; Li, F.K.

1997-06-01

Ocean backscatter was measured by the Jet Propulsion Laboratory, with the airborne NUSCAT K{sub u}-band scatterometer, across the Gulf Stream sea surface temperature front during the Surface Wave Dynamics Experiment off the coast of Virginia and Maryland in the winter of 1991. Backscatter across the front between the National Oceanic and Atmospheric Administration experimental coastal buoy A (44024) on the cold side and Discus C buoy (44023) on the warm side shows a difference of more than 5 dB for vertical polarization in many cases. This large frontal backscatter change is observed in all upwind, downwind, and crosswind directions. Themore » sea surface temperature difference measured by the buoys was about 9{degrees}C. The corresponding difference in wind speed cannot account for the large backscatter change in view of geophysical model functions depending only on neutral wind velocity such as SASS. The measured backscatter also has larger upwind-downwind and upwind-crosswind ratios compared to the model results. Furthermore, NUSCAT data reveal that upwind backscatter on the cold side was smaller than or close to crosswind backscatter on the warm side for incidence angles between 30{degrees} to 50{degrees}. This suggests that the temperature front can be detected by the scatterometer at these incidence angles for different wind directions in the cold and warm sides.« less

Late Paleocene Arctic Ocean shallow-marine temperatures from mollusc stable isotopes

USGS Publications Warehouse

Bice, Karen L.; Arthur, Michael A.; Marincovich, Louie

1996-01-01

Late Paleocene high-latitude (80°N) Arctic Ocean shallow-marine temperatures are estimated from molluscan δ18O time series. Sampling of individual growth increments of two specimens of the bivalve Camptochlamys alaskensis provides a high-resolution record of shell stable isotope composition. The heavy carbon isotopic values of the specimens support a late Paleocene age for the youngest marine beds of the Prince Creek Formation exposed near Ocean Point, Alaska. The oxygen isotopic composition of regional freshwater runoff is estimated from the mean δ18O value of two freshwater bivalves collected from approximately coeval fluviatile beds. Over a 30 – 34‰ range of salinity, values assumed to represent the tolerance of C. alaskensis, the mean annual shallow-marine temperature recorded by these individuals is between 11° and 22°C. These values could represent maximum estimates of the mean annual temperature because of a possible warm-month bias imposed on the average δ18O value by slowing or cessation of growth in winter months. The amplitude of the molluscan δ18O time series probably records most of the seasonality in shallow-marine temperature. The annual temperature range indicated is approximately 6°C, suggesting very moderate high-latitude marine temperature seasonality during the late Paleocene. On the basis of analogy with modern Chlamys species, C. alaskensis probably inhabited water depths of 30–50 m. The seasonal temperature range derived from δ18O is therefore likely to be damped relative to the full range of annual sea surface temperatures. High-resolution sampling of molluscan shell material across inferred growth bands represents an important proxy record of seasonality of marine and freshwater conditions applicable at any latitude. If applied to other regions and time periods, the approach used here would contribute substantially to the paleoclimate record of seasonality.

Contrasting temperature trends across the ice-free part of Greenland.

PubMed

Westergaard-Nielsen, Andreas; Karami, Mojtaba; Hansen, Birger Ulf; Westermann, Sebastian; Elberling, Bo

2018-01-25

Temperature changes in the Arctic have notable impacts on ecosystem structure and functioning, on soil carbon dynamics, and on the stability of permafrost, thus affecting ecosystem functions and putting man-built infrastructure at risk. Future warming in the Arctic could accelerate important feedbacks in permafrost degradation processes. Therefore it is important to map vulnerable areas most likely to be impacted by temperature changes and at higher risk of degradation, particularly near communities, to assist adaptation to climate change. Currently, these areas are poorly assessed, especially in Greenland. Here we quantify trends in satellite-derived land surface temperatures and modelled air temperatures, validated against observations, across the entire ice-free Greenland. Focus is on the past 30 years, to characterize significant changes and potentially vulnerable regions at a 1 km resolution. We show that recent temperature trends in Greenland vary significantly between seasons and regions and that data with resolutions down to single km 2 are critical to map temperature changes for guidance of further local studies and decision-making. Only a fraction of the ice-free Greenland seems vulnerable due to warming when analyzing year 2001-2015, but the most pronounced changes are found in the most populated parts of Greenland. As Greenland represents important gradients of north/south coast/inland/distance to large ice sheets, the conclusions are also relevant in an upscaling to greater Arctic areas.

Depth perception: the need to report ocean biogeochemical rates as functions of temperature, not depth.

PubMed

Brewer, Peter G; Peltzer, Edward T

2017-09-13

For over 50 years, ocean scientists have oddly represented ocean oxygen consumption rates as a function of depth but not temperature in most biogeochemical models. This unique tradition or tactic inhibits useful discussion of climate change impacts, where specific and fundamental temperature-dependent terms are required. Tracer-based determinations of oxygen consumption rates in the deep sea are nearly universally reported as a function of depth in spite of their well-known microbial basis. In recent work, we have shown that a carefully determined profile of oxygen consumption rates in the Sargasso Sea can be well represented by a classical Arrhenius function with an activation energy of 86.5 kJ mol -1 , leading to a Q 10 of 3.63. This indicates that for 2°C warming, we will have a 29% increase in ocean oxygen consumption rates, and for 3°C warming, a 47% increase, potentially leading to large-scale ocean hypoxia should a sufficient amount of organic matter be available to microbes. Here, we show that the same principles apply to a worldwide collation of tracer-based oxygen consumption rate data and that some 95% of ocean oxygen consumption is driven by temperature, not depth, and thus will have a strong climate dependence. The Arrhenius/Eyring equations are no simple panacea and they require a non-equilibrium steady state to exist. Where transient events are in progress, this stricture is not obeyed and we show one such possible example.This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'. © 2017 The Author(s).

Combined effects of recent Pacific cooling and Indian Ocean warming on the Asian monsoon.

PubMed

Ueda, Hiroaki; Kamae, Youichi; Hayasaki, Masamitsu; Kitoh, Akio; Watanabe, Shigeru; Miki, Yurisa; Kumai, Atsuki

2015-11-13

Recent research indicates that the cooling trend in the tropical Pacific Ocean over the past 15 years underlies the contemporaneous hiatus in global mean temperature increase. During the hiatus, the tropical Pacific Ocean displays a La Niña-like cooling pattern while sea surface temperature (SST) in the Indian Ocean has continued to increase. This SST pattern differs from the well-known La Niña-induced basin-wide cooling across the Indian Ocean on the interannual timescale. Here, based on model experiments, we show that the SST pattern during the hiatus explains pronounced regional anomalies of rainfall in the Asian monsoon region and thermodynamic effects due to specific humidity change are secondary. Specifically, Indo-Pacific SST anomalies cause convection to intensify over the tropical western Pacific, which in turn suppresses rainfall in mid-latitude East Asia through atmospheric teleconnection. Overall, the tropical Pacific SST effect opposes and is greater than the Indian Ocean SST effect.

An objective algorithm for reconstructing the three-dimensional ocean temperature field based on Argo profiles and SST data

NASA Astrophysics Data System (ADS)

Zhou, Chaojie; Ding, Xiaohua; Zhang, Jie; Yang, Jungang; Ma, Qiang

2017-12-01

While global oceanic surface information with large-scale, real-time, high-resolution data is collected by satellite remote sensing instrumentation, three-dimensional (3D) observations are usually obtained from in situ measurements, but with minimal coverage and spatial resolution. To meet the needs of 3D ocean investigations, we have developed a new algorithm to reconstruct the 3D ocean temperature field based on the Array for Real-time Geostrophic Oceanography (Argo) profiles and sea surface temperature (SST) data. The Argo temperature profiles are first optimally fitted to generate a series of temperature functions of depth, with the vertical temperature structure represented continuously. By calculating the derivatives of the fitted functions, the calculation of the vertical temperature gradient of the Argo profiles at an arbitrary depth is accomplished. A gridded 3D temperature gradient field is then found by applying inverse distance weighting interpolation in the horizontal direction. Combined with the processed SST, the 3D temperature field reconstruction is realized below the surface using the gridded temperature gradient. Finally, to confirm the effectiveness of the algorithm, an experiment in the Pacific Ocean south of Japan is conducted, for which a 3D temperature field is generated. Compared with other similar gridded products, the reconstructed 3D temperature field derived by the proposed algorithm achieves satisfactory accuracy, with correlation coefficients of 0.99 obtained, including a higher spatial resolution (0.25° × 0.25°), resulting in the capture of smaller-scale characteristics. Finally, both the accuracy and the superiority of the algorithm are validated.

Recent trends in energy flows through the Arctic climate system

NASA Astrophysics Data System (ADS)

Mayer, Michael; Haimberger, Leo

2016-04-01

While Arctic climate change can be diagnosed in many parameters, a comprehensive assessment of long-term changes and low frequency variability in the coupled Arctic energy budget still remains challenging due to the complex physical processes involved and the lack of observations. Here we draw on strongly improved observational capabilities of the past 15 years and employ observed radiative fluxes from CERES along with state-of-the-art atmospheric as well as coupled ocean-ice reanalyses to explore recent changes in energy flows through the Arctic climate system. Various estimates of ice volume and ocean heat content trends imply that the energy imbalance of the Arctic climate system was >1 Wm-2 during the 2000-2015 period, where most of the extra heat warmed the ocean and a comparatively small fraction was used to melt sea ice. The energy imbalance was partly fed by enhanced oceanic heat transports into the Arctic, especially in the mid 2000s. Seasonal trends of net radiation show a very clear signal of the ice-albedo feedback. Stronger radiative energy input during summer means increased seasonal oceanic heat uptake and accelerated sea ice melt. In return, lower minimum sea ice extent and higher SSTs lead to enhanced heat release from the ocean during fall season. These results are consistent with modeling studies finding an enhancement of the annual cycle of surface energy exchanges in a warming Arctic. Moreover, stronger heat fluxes from the ocean to the atmosphere in fall tend to warm the arctic boundary layer and reduce meridional temperature gradients, thereby reducing atmospheric energy transports into the polar cap. Although the observed results are a robust finding, extended high-quality datasets are needed to reliably separate trends from low frequency variability.

Multi-decadal trend and space-time variability of sea level over the Indian Ocean since the 1950s: impact of decadal climate modes

NASA Astrophysics Data System (ADS)

Han, W.; Stammer, D.; Meehl, G. A.; Hu, A.; Sienz, F.

2016-12-01

Sea level varies on decadal and multi-decadal timescales over the Indian Ocean. The variations are not spatially uniform, and can deviate considerably from the global mean sea level rise (SLR) due to various geophysical processes. One of these processes is the change of ocean circulation, which can be partly attributed to natural internal modes of climate variability. Over the Indian Ocean, the most influential climate modes on decadal and multi-decadal timescales are the Interdecadal Pacific Oscillation (IPO) and decadal variability of the Indian Ocean dipole (IOD). Here, we first analyze observational datasets to investigate the impacts of IPO and IOD on spatial patterns of decadal and interdecadal (hereafter decal) sea level variability & multi-decadal trend over the Indian Ocean since the 1950s, using a new statistical approach of Bayesian Dynamical Linear regression Model (DLM). The Bayesian DLM overcomes the limitation of "time-constant (static)" regression coefficients in conventional multiple linear regression model, by allowing the coefficients to vary with time and therefore measuring "time-evolving (dynamical)" relationship between climate modes and sea level. For the multi-decadal sea level trend since the 1950s, our results show that climate modes and non-climate modes (the part that cannot be explained by climate modes) have comparable contributions in magnitudes but with different spatial patterns, with each dominating different regions of the Indian Ocean. For decadal variability, climate modes are the major contributors for sea level variations over most region of the tropical Indian Ocean. The relative importance of IPO and decadal variability of IOD, however, varies spatially. For example, while IOD decadal variability dominates IPO in the eastern equatorial basin (85E-100E, 5S-5N), IPO dominates IOD in causing sea level variations in the tropical southwest Indian Ocean (45E-65E, 12S-2S). To help decipher the possible contribution of external

Causes of Upper-Ocean Temperature Anomalies in the Tropical North Atlantic

NASA Astrophysics Data System (ADS)

Rugg, A.; Foltz, G. R.; Perez, R. C.

2016-02-01

Hurricane activity and regional rainfall are strongly impacted by upper ocean conditions in the tropical North Atlantic, defined as the region between the equator and 20°N. A previous study analyzed a strong cold sea surface temperature (SST) anomaly that developed in this region during early 2009 and was recorded by the Pilot Research Array in the Tropical Atlantic (PIRATA) moored buoy at 4°N, 23°W (Foltz et al. 2012). The same mooring shows a similar cold anomaly in the spring of 2015 as well as a strong warm anomaly in 2010, offering the opportunity for a more comprehensive analysis of the causes of these events. In this study we examine the main causes of the observed temperature anomalies between 1998 and 2015. Basin-scale conditions during these events are analyzed using satellite SST, wind, and rain data, as well as temperature and salinity profiles from the NCEP Global Ocean Data Assimilation System. A more detailed analysis is conducted using ten years of direct measurements from the PIRATA mooring at 4°N, 23°W. Results show that the cooling and warming anomalies were caused primarily by wind-driven changes in surface evaporative cooling, mixed layer depth, and upper-ocean vertical velocity. Anomalies in surface solar radiation acted to damp the wind-driven SST anomalies in the latitude bands of the ITCZ (3°-8°N). Basin-scale analyses also suggest a strong connection between the observed SST anomalies and the Atlantic Meridional Mode, a well-known pattern of SST and surface wind anomalies spanning the tropical Atlantic.

A Test of Model Validation from Observed Temperature Trends

NASA Astrophysics Data System (ADS)

Singer, S. F.

2006-12-01

How much of current warming is due to natural causes and how much is manmade? This requires a comparison of the patterns of observed warming with the best available models that incorporate both anthropogenic (greenhouse gases and aerosols) as well as natural climate forcings (solar and volcanic). Fortunately, we have the just published U.S.-Climate Change Science Program (CCSP) report (www.climatescience.gov/Library/sap/sap1-1/finalreport/default.htm), based on best current information. As seen in Fig. 1.3F of the report, modeled surface temperature trends change little with latitude, except for a stronger warming in the Arctic. The observations, however, show a strong surface warming in the northern hemisphere but not in the southern hemisphere (see Fig. 3.5C and 3.6D). The Antarctic is found to be cooling and Arctic temperatures, while currently rising, were higher in the 1930s than today. Although the Executive Summary of the CCSP report claims "clear evidence" for anthropogenic warming, based on comparing tropospheric and surface temperature trends, the report itself does not confirm this. Greenhouse models indicate that the tropics should provide the most sensitive location for their validation; trends there should increase by 200-300 percent with altitude, peaking at around 10 kilometers. The observations, however, show the opposite: flat or even decreasing tropospheric trend values (see Fig. 3.7 and also Fig. 5.7E). This disparity is demonstrated most strikingly in Fig. 5.4G, which shows the difference between surface and troposphere trends for a collection of models (displayed as a histogram) and for balloon and satellite data. [The disparities are less apparent in the Summary, which displays model results in terms of "range" rather than as histograms.] There may be several possible reasons for the disparity: Instrumental and other effects that exaggerate or otherwise distort observed temperature trends. Or, more likely: Shortcomings in models that result

Orbital-scale Central Arctic Ocean Temperature Records from Benthic Foraminiferal δ18O and Ostracode Mg/Ca Ratios

NASA Astrophysics Data System (ADS)

Keller, K.; Cronin, T. M.; Dwyer, G. S.; Farmer, J. R.; Poirier, R. K.; Schaller, M. F.

2017-12-01

Orbital-scale climate variability is often amplified in the polar region, for example in changes in seawater temperature, sea-ice cover, deep-water formation, ecosystems, heat storage and carbon cycling. Yet, the relationship between the Arctic Ocean and global climate remains poorly understood due largely to limited orbital-scale paleoclimate records, the complicated nature of sea-ice response to climate and limited abundance of deep sea biological proxies. Here we reconstruct central Arctic Ocean bottom temperatures over the last 600 kyr using ostracode Mg/Ca ratios (genus Krithe) and benthic foraminiferal oxygen isotope ratios (δ18Obf - I. teretis, O. tener, P. bulloides, C. reniforme, C. wuellerstorfi) in six sediment cores recovered from the Mendeleev and Northwind Ridges (700- 2726 m water depth). We examined glacial-interglacial cycles in Arctic seawater temperatures and Arctic δ18Obf chronostratigraphy to reconcile effects of changing bottom water temperature, ice volume and regional hydrography on δ18Obf records. Results show lower ( 10-12 mmol/mol) interglacial and higher ( 16-23 mmol/mol) glacial Mg/Ca ratios, signifying intermediate depth ocean warming during glacials of up to 2 ºC. These temperature maxima are likely related to a deepening of the halocline and the corresponding deeper influence of warm Atlantic water. Glacial-interglacial δ18Obf ranges are smaller in the Arctic ( 0.8-1‰ VPDB) than in the global ocean ( 1.8 ‰). However, when the distinct glacial-interglacial temperature histories of the Arctic (glacial warming) and global ocean (glacial cooling) are accounted for, both Arctic and global ocean seawater δ18O values (δ18Osw) exhibit similar 1.2-1.3 ‰ glacial-interglacial ranges. Thus, Arctic δ18Obf confirms glacial Arctic warming inferred from ostracode Mg/Ca. This study will discuss the strengths and limitations of applying paired Mg/Ca and oxygen isotope proxies in reconstructing more robust paleoceanographic changes in the

Ocean heat content and ocean energy budget: make better use of historical global subsurface temperature dataset

NASA Astrophysics Data System (ADS)

Cheng, L.; Zhu, J.

2016-02-01

Ocean heat content (OHC) change contributes substantially to global sea level rise, also is a key metric of the ocean/global energy budget, so it is a vital task for the climate research community to estimate historical OHC. While there are large uncertainties regarding its value, here we review the OHC calculation by using the historical global subsurface temperature dataset, and discuss the sources of its uncertainty. The presentation briefly introduces how to correct to the systematic biases in expendable bathythermograph (XBT) data, a alternative way of filling data gaps (which is main focus of this talk), and how to choose a proper climatology. A new reconstruction of historical upper (0-700 m) OHC change will be presented, which is the Institute of Atmospheric Physics (IAP) version of historical upper OHC assessment. The authors also want to highlight the impact of observation system change on OHC calculation, which could lead to bias in OHC estimates. Furthermore, we will compare the updated observational-based estimates on ocean heat content change since 1970s with CMIP5 results. This comparison shows good agreement, increasing the confidence of the climate models in representing the climate history.

Estimating trends in atmospheric water vapor and temperature time series over Germany

NASA Astrophysics Data System (ADS)

Alshawaf, Fadwa; Balidakis, Kyriakos; Dick, Galina; Heise, Stefan; Wickert, Jens

2017-08-01

Ground-based GNSS (Global Navigation Satellite System) has efficiently been used since the 1990s as a meteorological observing system. Recently scientists have used GNSS time series of precipitable water vapor (PWV) for climate research. In this work, we compare the temporal trends estimated from GNSS time series with those estimated from European Center for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA-Interim) data and meteorological measurements. We aim to evaluate climate evolution in Germany by monitoring different atmospheric variables such as temperature and PWV. PWV time series were obtained by three methods: (1) estimated from ground-based GNSS observations using the method of precise point positioning, (2) inferred from ERA-Interim reanalysis data, and (3) determined based on daily in situ measurements of temperature and relative humidity. The other relevant atmospheric parameters are available from surface measurements of meteorological stations or derived from ERA-Interim. The trends are estimated using two methods: the first applies least squares to deseasonalized time series and the second uses the Theil-Sen estimator. The trends estimated at 113 GNSS sites, with 10 to 19 years temporal coverage, vary between -1.5 and 2.3 mm decade-1 with standard deviations below 0.25 mm decade-1. These results were validated by estimating the trends from ERA-Interim data over the same time windows, which show similar values. These values of the trend depend on the length and the variations of the time series. Therefore, to give a mean value of the PWV trend over Germany, we estimated the trends using ERA-Interim spanning from 1991 to 2016 (26 years) at 227 synoptic stations over Germany. The ERA-Interim data show positive PWV trends of 0.33 ± 0.06 mm decade-1 with standard errors below 0.03 mm decade-1. The increment in PWV varies between 4.5 and 6.5 % per degree Celsius rise in temperature, which is comparable to the theoretical rate of the Clausius

The impacts of oceanic deep temperature perturbations in the North Atlantic on decadal climate variability and predictability

NASA Astrophysics Data System (ADS)

Germe, Agathe; Sévellec, Florian; Mignot, Juliette; Fedorov, Alexey; Nguyen, Sébastien; Swingedouw, Didier

2017-12-01

Decadal climate predictability in the North Atlantic is largely related to ocean low frequency variability, whose sensitivity to initial conditions is not very well understood. Recently, three-dimensional oceanic temperature anomalies optimally perturbing the North Atlantic Mean Temperature (NAMT) have been computed via an optimization procedure using a linear adjoint to a realistic ocean general circulation model. The spatial pattern of the identified perturbations, localized in the North Atlantic, has the largest magnitude between 1000 and 4000 m depth. In the present study, the impacts of these perturbations on NAMT, on the Atlantic meridional overturning circulation (AMOC), and on climate in general are investigated in a global coupled model that uses the same ocean model as was used to compute the three-dimensional optimal perturbations. In the coupled model, these perturbations induce AMOC and NAMT anomalies peaking after 5 and 10 years, respectively, generally consistent with the ocean-only linear predictions. To further understand their impact, their magnitude was varied in a broad range. For initial perturbations with a magnitude comparable to the internal variability of the coupled model, the model response exhibits a strong signature in sea surface temperature and precipitation over North America and the Sahel region. The existence and impacts of these ocean perturbations have important implications for decadal prediction: they can be seen either as a source of predictability or uncertainty, depending on whether the current observing system can detect them or not. In fact, comparing the magnitude of the imposed perturbations with the uncertainty of available ocean observations such as Argo data or ocean state estimates suggests that only the largest perturbations used in this study could be detectable. This highlights the importance for decadal climate prediction of accurate ocean density initialisation in the North Atlantic at intermediate and greater

Surface wave effects in the NEMO ocean model: Forced and coupled experiments

NASA Astrophysics Data System (ADS)

Breivik, Øyvind; Mogensen, Kristian; Bidlot, Jean-Raymond; Balmaseda, Magdalena Alonso; Janssen, Peter A. E. M.

2015-04-01

The NEMO general circulation ocean model is extended to incorporate three physical processes related to ocean surface waves, namely the surface stress (modified by growth and dissipation of the oceanic wavefield), the turbulent kinetic energy flux from breaking waves, and the Stokes-Coriolis force. Experiments are done with NEMO in ocean-only (forced) mode and coupled to the ECMWF atmospheric and wave models. Ocean-only integrations are forced with fields from the ERA-Interim reanalysis. All three effects are noticeable in the extratropics, but the sea-state-dependent turbulent kinetic energy flux yields by far the largest difference. This is partly because the control run has too vigorous deep mixing due to an empirical mixing term in NEMO. We investigate the relation between this ad hoc mixing and Langmuir turbulence and find that it is much more effective than the Langmuir parameterization used in NEMO. The biases in sea surface temperature as well as subsurface temperature are reduced, and the total ocean heat content exhibits a trend closer to that observed in a recent ocean reanalysis (ORAS4) when wave effects are included. Seasonal integrations of the coupled atmosphere-wave-ocean model consisting of NEMO, the wave model ECWAM, and the atmospheric model of ECMWF similarly show that the sea surface temperature biases are greatly reduced when the mixing is controlled by the sea state and properly weighted by the thickness of the uppermost level of the ocean model. These wave-related physical processes were recently implemented in the operational coupled ensemble forecast system of ECMWF.

Trends in extreme daily temperatures and humidex index in the United Arab Emirates over 1948-2014.

NASA Astrophysics Data System (ADS)

Yang, H. W.; Ouarda, T.

2015-12-01

This study deals with the analysis of the characteristics of extreme temperature events in the Middle East, using NCEP reanalysis gridded data, for the summer (May-October) and winter (November-April) seasons. Trends in the occurrences of three types of heat spells during 1948-2014 are studied by both Linear Regression (LR) and Mann-Kendall (MK) test. Changes in the diurnal temperature range (DTR) are also investigated. To better understand the effects of heat spells on public health, the Humidex, a combination index of ambient temperature and relative humidity, is also used. Using percentile threshold, temperature (Humidex) Type-A and Type-B heat spells are defined respectively by daily maximum and minimum temperature (Humidex). Type-C heat spells are defined as the joint occurrence of Type-A and Type-B heat spells at the same time. In the Middle East, it is found that no coherent trend in temperature Type-A heat spells is observed. However, the occurrences of temperature Type-B and C heat spells have consistently increased since 1948. For Humidex heat spells, coherently increased activities of all three types of heat spells are observed in the area. During the summer, the magnitude of the positive trends in Humidex heat spells are generally stronger than temperature heat spells. More than half of the locations in the area show significantly negative DTR trends in the summer, but the trends vary according to the region in the winter. Annual mean temperature has increased an average by 0.5°C, but it is mainly associated with the daily minimum temperature which has warmed up by 0.84°C.Daily maximum temperature showed no significant trends. The warming is hence stronger in minimum temperatures than in maximum temperatures resulting in a decrease in DTR by 0.16 °C per decade. This study indicates hence that the UAE has not become hotter, but it has become less cold during 1948 to 2014.

Sea Surface Temperature and Ocean Color Variability in the South China Sea

NASA Astrophysics Data System (ADS)

Conaty, A. P.

2001-12-01

The South China Sea is a marginal sea in the Southeast Asian region whose surface circulation is driven by monsoons and whose surface currents have complex seasonal patterns. Its rich natural resources and strategic location have made its small islands areas of political dispute among the neighboring nations. This study aims to show the seasonal and interannual variability of sea surface temperature and ocean color in South China Sea. It makes use of NOAA's Advanced Very High Resolution Radiometer (AVHRR) satellite data sets on sea surface temperature for the period 1981-2000 and NASA's Nimbus-7 Coastal Zone Color Scanner (CZCS) and Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite data sets on pigment concentration (ocean color) for the period 1981-1996 and 1997-2000, respectively. Transect lines were drawn along several potential hotspot areas to show the variability in sea surface temperature and pigment concentration through time. In-situ data on sea surface temperature along South China Sea were likewise plotted to see the variability with time. Higher seasonal variability in sea surface temperature was seen at higher latitudes. Interannual variability was within 1-3 Kelvin. In most areas, pigment concentration was higher during northern hemisphere winter and autumn, after the monsoon rains, with a maximum of 30 milligrams per cubic meter.

Ocean heat content variability and change in an ensemble of ocean reanalyses

NASA Astrophysics Data System (ADS)

Palmer, M. D.; Roberts, C. D.; Balmaseda, M.; Chang, Y.-S.; Chepurin, G.; Ferry, N.; Fujii, Y.; Good, S. A.; Guinehut, S.; Haines, K.; Hernandez, F.; Köhl, A.; Lee, T.; Martin, M. J.; Masina, S.; Masuda, S.; Peterson, K. A.; Storto, A.; Toyoda, T.; Valdivieso, M.; Vernieres, G.; Wang, O.; Xue, Y.

2017-08-01

Accurate knowledge of the location and magnitude of ocean heat content (OHC) variability and change is essential for understanding the processes that govern decadal variations in surface temperature, quantifying changes in the planetary energy budget, and developing constraints on the transient climate response to external forcings. We present an overview of the temporal and spatial characteristics of OHC variability and change as represented by an ensemble of dynamical and statistical ocean reanalyses (ORAs). Spatial maps of the 0-300 m layer show large regions of the Pacific and Indian Oceans where the interannual variability of the ensemble mean exceeds ensemble spread, indicating that OHC variations are well-constrained by the available observations over the period 1993-2009. At deeper levels, the ORAs are less well-constrained by observations with the largest differences across the ensemble mostly associated with areas of high eddy kinetic energy, such as the Southern Ocean and boundary current regions. Spatial patterns of OHC change for the period 1997-2009 show good agreement in the upper 300 m and are characterized by a strong dipole pattern in the Pacific Ocean. There is less agreement in the patterns of change at deeper levels, potentially linked to differences in the representation of ocean dynamics, such as water mass formation processes. However, the Atlantic and Southern Oceans are regions in which many ORAs show widespread warming below 700 m over the period 1997-2009. Annual time series of global and hemispheric OHC change for 0-700 m show the largest spread for the data sparse Southern Hemisphere and a number of ORAs seem to be subject to large initialization `shock' over the first few years. In agreement with previous studies, a number of ORAs exhibit enhanced ocean heat uptake below 300 and 700 m during the mid-1990s or early 2000s. The ORA ensemble mean (±1 standard deviation) of rolling 5-year trends in full-depth OHC shows a relatively steady

Diversity of deep-water cetaceans in relation to temperature: implications for ocean warming.

PubMed

Whitehead, Hal; McGill, Brian; Worm, Boris

2008-11-01

Understanding the effects of natural environmental variation on biodiversity can help predict response to future anthropogenic change. Here we analyse a large, long-term data set of sightings of deep-water cetaceans from the Atlantic, Pacific and Indian Oceans. Seasonal and geographic changes in the diversity of these genera are well predicted by a convex function of sea-surface temperature peaking at c. 21 degrees C. Thus, diversity is highest at intermediate latitudes - an emerging general pattern for the pelagic ocean. When applied to a range of Intergovernmental Panel on Climate Change global change scenarios, the predicted response is a decline of cetacean diversity across the tropics and increases at higher latitudes. This suggests that deep-water oceanic communities that dominate > 60% of the planet's surface may reorganize in response to ocean warming, with low-latitude losses of diversity and resilience.

Long-term trends in stratospheric ozone, temperature, and water vapor over the Indian region

NASA Astrophysics Data System (ADS)

Thankamani Akhil Raj, Sivan; Venkat Ratnam, Madineni; Narayana Rao, Daggumati; Venkata Krishna Murthy, Boddam

2018-01-01

We have investigated the long-term trends in and variabilities of stratospheric ozone, water vapor and temperature over the Indian monsoon region using the long-term data constructed from multi-satellite (Upper Atmosphere Research Satellite (UARS MLS and HALOE, 1993-2005), Aura Microwave Limb Sounder (MLS, 2004-2015), Sounding of the Atmosphere using Broadband Emission Radiometry (SABER, 2002-2015) on board TIMED (Thermosphere Ionosphere Mesosphere Energetics Dynamics)) observations covering the period 1993-2015. We have selected two locations, namely, Trivandrum (8.4° N, 76.9° E) and New Delhi (28° N, 77° E), covering northern and southern parts of the Indian region. We also used observations from another station, Gadanki (13.5° N, 79.2° E), for comparison. A decreasing trend in ozone associated with NOx chemistry in the tropical middle stratosphere is found, and the trend turned to positive in the upper stratosphere. Temperature shows a cooling trend in the stratosphere, with a maximum around 37 km over Trivandrum (-1.71 ± 0.49 K decade-1) and New Delhi (-1.15 ± 0.55 K decade-1). The observed cooling trend in the stratosphere over Trivandrum and New Delhi is consistent with Gadanki lidar observations during 1998-2011. The water vapor shows a decreasing trend in the lower stratosphere and an increasing trend in the middle and upper stratosphere. A good correlation between N2O and O3 is found in the middle stratosphere (˜ 10 hPa) and poor correlation in the lower stratosphere. There is not much regional difference in the water vapor and temperature trends. However, upper stratospheric ozone trends over Trivandrum and New Delhi are different. The trend analysis carried out by varying the initial year has shown significant changes in the estimated trend.

Global, Regional, and Megacity Trends in the Highest Temperature of the Year: Diagnostics and Evidence for Accelerating Trends

NASA Astrophysics Data System (ADS)

Papalexiou, Simon Michael; AghaKouchak, Amir; Trenberth, Kevin E.; Foufoula-Georgiou, Efi

2018-01-01

Trends in short-lived high-temperature extremes record a different dimension of change than the extensively studied annual and seasonal mean daily temperatures. They also have important socioeconomic, environmental, and human health implications. Here, we present analysis of the highest temperature of the year for approximately 9000 stations globally, focusing on quantifying spatially explicit exceedance probabilities during the recent 50- and 30-year periods. A global increase of 0.19°C per decade during the past 50 years (through 2015) accelerated to 0.25°C per decade during the last 30 years, a faster increase than in the mean annual temperature. Strong positive 30-year trends are detected in large regions of Eurasia and Australia with rates higher than 0.60°C per decade. In cities with more than 5 million inhabitants, where most heat-related fatalities occur, the average change is 0.33°C per decade, while some east Asia cities, Paris, Moscow, and Houston have experienced changes higher than 0.60°C per decade.

Global, Regional, and Megacity Trends in the Highest Temperature of the Year: Diagnostics and Evidence for Accelerating Trends.

PubMed

Papalexiou, Simon Michael; AghaKouchak, Amir; Trenberth, Kevin E; Foufoula-Georgiou, Efi

2018-01-01

Trends in short-lived high-temperature extremes record a different dimension of change than the extensively studied annual and seasonal mean daily temperatures. They also have important socioeconomic, environmental, and human health implications. Here, we present analysis of the highest temperature of the year for approximately 9000 stations globally, focusing on quantifying spatially explicit exceedance probabilities during the recent 50- and 30-year periods. A global increase of 0.19°C per decade during the past 50 years (through 2015) accelerated to 0.25°C per decade during the last 30 years, a faster increase than in the mean annual temperature. Strong positive 30-year trends are detected in large regions of Eurasia and Australia with rates higher than 0.60°C per decade. In cities with more than 5 million inhabitants, where most heat-related fatalities occur, the average change is 0.33°C per decade, while some east Asia cities, Paris, Moscow, and Houston have experienced changes higher than 0.60°C per decade.

Warming Trends and Bleaching Stress of the World’s Coral Reefs 1985-2012

NASA Astrophysics Data System (ADS)

Heron, Scott F.; Maynard, Jeffrey A.; van Hooidonk, Ruben; Eakin, C. Mark

2016-12-01

Coral reefs across the world’s oceans are in the midst of the longest bleaching event on record (from 2014 to at least 2016). As many of the world’s reefs are remote, there is limited information on how past thermal conditions have influenced reef composition and current stress responses. Using satellite temperature data for 1985-2012, the analysis we present is the first to quantify, for global reef locations, spatial variations in warming trends, thermal stress events and temperature variability at reef-scale (~4 km). Among over 60,000 reef pixels globally, 97% show positive SST trends during the study period with 60% warming significantly. Annual trends exceeded summertime trends at most locations. This indicates that the period of summer-like temperatures has become longer through the record, with a corresponding shortening of the ‘winter’ reprieve from warm temperatures. The frequency of bleaching-level thermal stress increased three-fold between 1985-91 and 2006-12 - a trend climate model projections suggest will continue. The thermal history data products developed enable needed studies relating thermal history to bleaching resistance and community composition. Such analyses can help identify reefs more resilient to thermal stress.

Detection and Attribution of Temperature Trends in the Presence of Natural Variability

NASA Astrophysics Data System (ADS)

Wallace, J. M.

2014-12-01

The fingerprint of human-induced global warming stands out clearly above the noise In the time series of global-mean temperature, but not local temperature. At extratropical latitudes over land the standard error of 50-year linear temperature trends at a fixed point is as large as the cumulative rise in global-mean temperature over the past century. Much of the samping variability in local temperature trends is "dynamically-induced", i.e., attributable to the fact that the seasonally-varying mean circulation varies substantially from one year to the next and anomalous circulation patterns are generally accompanied by anomalous temperature patterns. In the presence of such large sampling variability it is virtually impossible to identify the spatial signature of greenhouse warming based on observational data or to partition observed local temperature trends into natural and human-induced components. It follows that previous IPCC assessments, which have focused on the deterministic signature of human-induced climate change, are inherently limited as to what they can tell us about the attribution of the past record of local temperature change or about how much the temperature at a particular place is likely to rise in the next few decades in response to global warming. To obtain more informative assessments of regional and local climate variability and change it will be necessary to take a probabilistic approach. Just as the use of the ensembles has contributed to more informative extended range weather predictions, large ensembles of climate model simulations can provide a statistical context for interpreting observed climate change and for framing projections of future climate. For some purposes, statistics relating to the interannual variability in the historical record can serve as a surrogate for statistics relating to the diversity of climate change scenarios in large ensembles.

Surface Temperature variability from AIRS.

NASA Astrophysics Data System (ADS)

Ruzmaikin, A.; Dang, V. T.; Aumann, H. H.

2015-12-01

To address the existence and possible causes of the climate hiatus in the Earth's global temperature we investigate the trends and variability in the surface temperature using retrievals obtained from the measurements by the Atmospheric Infrared Sounder (AIRS) and its companion instrument, the Advanced Microwave Sounding Unit (AMSU), onboard of Aqua spacecraft in 2002-2014for the day and night conditions. The data used are L3 monthly means on a 1x1degree spatial grid. We separate the land and ocean temperatures, as well as temperatures in Artic, Antarctic and desert regions. We compare the satellite data with the new surface data produced by Karl et al. (2015) who denies the reality of the climate hiatus. The difference in the regional trends can help to explain why the global surface temperature remains almost unchanged but the frequency of occurrence of the extreme events increases under rising anthropogenic forcing. The day-night difference is an indicator of the anthropogenic trend. This work was supported by the Jet Propulsion Laboratory of the California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

The seasonal response of the Held-Suarez climate model to prescribed ocean temperature anomalies. II - Dynamical analysis

NASA Technical Reports Server (NTRS)

Phillips, T. J.

1984-01-01

The heating associated with equatorial, subtropical, and midlatitude ocean temperature anamolies in the Held-Suarez climate model is analyzed. The local and downstream response to the anomalies is analyzed, first by examining the seasonal variation in heating associated with each ocean temperature anomaly, and then by combining knowledge of the heating with linear dynamical theory in order to develop a more comprehensive explanation of the seasonal variation in local and downstream atmospheric response to each anomaly. The extent to which the linear theory of propagating waves can assist the interpretation of the remote cross-latitudinal response of the model to the ocean temperature anomalies is considered. Alternative hypotheses that attempt to avoid the contradictions inherent in a strict application of linear theory are investigated, and the impact of sampling errors on the assessment of statistical significance is also examined.

Combined effects of ocean acidification and temperature on planula larvae of the moon jellyfish Aurelia coerulea.

PubMed

Dong, Zhijun; Sun, Tingting

2018-08-01

Rapidly rising levels of atmospheric CO 2 have caused two environmental stressors, ocean acidification and seawater temperature increases, which represent major abiotic threats to marine organisms. Here, we investigated for the first time the combined effects of ocean acidification and seawater temperature increases on the behavior, survival, and settlement of the planula larvae of Aurelia coerulea, which is considered a nuisance species around the world. Three pH levels (8.1, 7.7 and 7.3) and two temperature levels (24 °C and 27 °C) were used in the present study. There were no interactive effects of temperature and pH on the behavior, survival, and settlement of planula larvae of A. coerulea. We found that the swimming speed and mortality of the planula larvae of A. coerulea were significantly affected by temperature, and low pH significantly affected settlement. Planula larvae of A. coerulea from the elevated temperature treatment moved faster and showed higher mortality than those at the control temperature. The settlement rate of A. coerulea planulae was significantly higher at the pH level of 7.3 than at other pH levels. These results suggest that seawater temperature increase, rather than reduced pH, was the main stress factor affecting the survival of A. coerulea planulae. Overall, the planula larvae of the common jellyfish A. coerulea appeared to be resistant to ocean acidification, but may be negatively affected by future seawater temperature increases. Copyright © 2018 Elsevier Ltd. All rights reserved.

The Cooling Oceanic Lithosphere as Constrained by Surface Wave Dispersion Data

NASA Astrophysics Data System (ADS)

Hogg, C.; Laske, G.

2003-12-01

The tremendous improvement in resolution capabilities of global surface wave phase velocity maps now encourage us to search for anomalies that are caused by mantle plumes. On the other hand, the implications of even large--scale anomalies in such maps are still not well understood. One such anomaly is caused by the cooling oceanic lithosphere. Some studies investigate the cooling effects by fitting thermal models to the 3--dimensional mantle models resulting from tomographic inversions. The inversion of surface wave data for structure at depth is nonunique and the model often depends on the techniques applied. We prefer to compare the dispersion data directly with predictions from thermal models. Simple cooling models produce a signal that is roughly proportional to the square root of age. This signal is typically much smaller than the one caused by other lateral heterogeneity within the Earth's crust and upper mantle. In a careful analysis we are able to extract clear, roughly linear trends, in all major oceans. We explore the parameter space by fitting cooling half space as well as cooling plate models to the data. In the Pacific ocean, our data are inconsistent with standard parameters that are used to fit the observed bathymetry, and perhaps surface heat flux data. Instead of an initial temperature of 1350~deg C in the cooling half space model our data require a lower temperature (around 1200~deg C) to be well fit, especially the Love wave data. Regarding the cooling plate model, our data seem to require a thicker lithosphere to be well fit (135~km instead of the 'standard' 100 ~m). We observe similar trends for the other oceans investigated: the Indian ocean, the South and the North Atlantic oceans. For the Indian ocean in particular, a crust correction (removing the predictions caused by crustal structure including water depth and sediment thickness) is crucial to obtain an internally consistent dataset. For the Atlantic ocean, a large signal remains

Differences between radiosonde and dropsonde temperature profiles over the Arctic Ocean

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skony, S.M.; Kahl, J.D.W.; Zaitseva, N.A.

1994-10-01

The boundary layer structure measured by 402 pairs of approximately collocated radiosonde and dropsonde temperature profiles over the Arctic Ocean during the period 1957-1961 is examined. The radiosonde profiles were obtained at the Russian drifting ice camps `North Pole 7` and `North Pole 8,` and the dropsonde profiles were measured during the United States Air Force `Ptarmigan` series of weather reconnaissance flights. The boundary layer structure is characterized by the features of the low-level tropospheric temperature inversion. The results indicate that the dropsonde soundings, although containing relatively few measurement levels, contain sufficient vertical resolution to characterize the temperature inversion. Systematicmore » differences were noted in wintertime inversion features and near-surface temperatures as measured by dropsondes and radiosondes. These differences are attributed to contrasting temperature lag errors accompanying ascending and descending sensors.« less

Estimating stratospheric temperature trends using satellite microwave radiances

NASA Technical Reports Server (NTRS)

Hudson, Robert D.; Newman, Paul A.; Schoeberl, Mark R.

1990-01-01

The objective was to evaluate and intercompare stratospheric temperatures using Microwave Sounding Unit (MSU) data as a basis data set. The MSU, aboard the NOAA polar orbiter satellite series, provides twice daily global coverage over a layer (50-150 mb) at approximately a (170km)(exp 2) resolution. Conventional data sets will be compared to the satellite data in the lower stratosphere in order to assess their quality for trend computations.

Estimation of the Ocean Skin Temperature using the NASA GEOS Atmospheric Data Assimilation System

NASA Technical Reports Server (NTRS)

Koster, Randal D.; Akella, Santha; Todling, Ricardo; Suarez, Max

2016-01-01

This report documents the status of the development of a sea surface temperature (SST) analysis for the Goddard Earth Observing System (GEOS) Version-5 atmospheric data assimilation system (ADAS). Its implementation is part of the steps being taken toward the development of an integrated earth system analysis. Currently, GEOS-ADAS SST is a bulk ocean temperature (from ocean boundary conditions), and is almost identical to the skin sea surface temperature. Here we describe changes to the atmosphere-ocean interface layer of the GEOS-atmospheric general circulation model (AGCM) to include near surface diurnal warming and cool-skin effects. We also added SST relevant Advanced Very High Resolution Radiometer (AVHRR) observations to the GEOS-ADAS observing system. We provide a detailed description of our analysis of these observations, along with the modifications to the interface between the GEOS atmospheric general circulation model, gridpoint statistical interpolation-based atmospheric analysis and the community radiative transfer model. Our experiments (with and without these changes) show improved assimilation of satellite radiance observations. We obtained a closer fit to withheld, in-situ buoys measuring near-surface SST. Evaluation of forecast skill scores corroborate improvements seen in the observation fits. Along with a discussion of our results, we also include directions for future work.

Experimental constraints on the damp peridotite solidus and oceanic mantle potential temperature

NASA Astrophysics Data System (ADS)

Sarafian, Emily; Gaetani, Glenn A.; Hauri, Erik H.; Sarafian, Adam R.

2017-03-01

Decompression of hot mantle rock upwelling beneath oceanic spreading centers causes it to exceed the melting point (solidus), producing magmas that ascend to form basaltic crust ~6 to 7 kilometers thick. The oceanic upper mantle contains ~50 to 200 micrograms per gram of water (H2O) dissolved in nominally anhydrous minerals, which—relative to its low concentration—has a disproportionate effect on the solidus that has not been quantified experimentally. Here, we present results from an experimental determination of the peridotite solidus containing known amounts of dissolved hydrogen. Our data reveal that the H2O-undersaturated peridotite solidus is hotter than previously thought. Reconciling geophysical observations of the melting regime beneath the East Pacific Rise with our experimental results requires that existing estimates for the oceanic upper mantle potential temperature be adjusted upward by about 60°C.

Decreased calcification in the Southern Ocean over the satellite record

NASA Astrophysics Data System (ADS)

Freeman, Natalie M.; Lovenduski, Nicole S.

2015-03-01

Widespread ocean acidification is occurring as the ocean absorbs anthropogenic carbon dioxide from the atmosphere, threatening marine ecosystems, particularly the calcifying plankton that provide the base of the marine food chain and play a key role within the global carbon cycle. We use satellite estimates of particulate inorganic carbon (PIC), surface chlorophyll, and sea surface temperature to provide a first estimate of changing calcification rates throughout the Southern Ocean. From 1998 to 2014 we observe a 4% basin-wide reduction in summer calcification, with ˜9% reductions in large regions (˜1 × 106 km2) of the Pacific and Indian sectors. Southern Ocean trends are spatially heterogeneous and primarily driven by changes in PIC concentration (suspended calcite), which has declined by ˜24% in these regions. The observed decline in Southern Ocean calcification and PIC is suggestive of large-scale changes in the carbon cycle and provides insight into organism vulnerability in a changing environment.

Cycles in oceanic teleconnections and global temperature change

NASA Astrophysics Data System (ADS)

Seip, Knut L.; Grøn, Øyvind

2018-06-01

Three large ocean currents are represented by proxy time series: the North Atlantic Oscillation (NAO), the Southern Oscillation Index (SOI), and the Pacific Decadal Oscillation (PDO). We here show how proxies for the currents interact with each other and with the global temperature anomaly (GTA). Our results are obtained by a novel method, which identifies running average leading-lagging (LL) relations, between paired series. We find common cycle times for a paired series of 6-7 and 25-28 years and identify years when the LL relations switch. Switching occurs with 18.4 ± 14.3-year intervals for the short 6-7-year cycles and with 27 ± 15-year intervals for the 25-28-year cycles. During the period 1940-1950, the LL relations for the long cycles were circular (nomenclature x leads y: x → y): GTA → NAO → SOI → PDO → GTA. However, after 1960, the LL relations become more complex and there are indications that GTA leads to both NAO and PDO. The switching years are related to ocean current tie points and reversals reported in the literature.

Temperature and Precipitation trends in Kashmir valley, North Western Himalayas

NASA Astrophysics Data System (ADS)

Shafiq, Mifta Ul; Rasool, Rehana; Ahmed, Pervez; Dimri, A. P.

2018-01-01

Climate change has emerged as an important issue ever to confront mankind. This concern emerges from the fact that our day-to-day activities are leading to impacts on the Earth's atmosphere that has the potential to significantly alter the planet's shield and radiation balance. Developing countries particularly whose income is particularly derived from agricultural activities are at the forefront of bearing repercussions due to changing climate. The present study is an effort to analyze the changing trends of precipitation and temperature variables in Kashmir valley along different elevation zones in the north western part of India. As the Kashmir valley has a rich repository of glaciers with its annual share of precipitation, slight change in the temperature and precipitation regime has far reaching environmental and economic consequences. The results from Indian Meteorological Department (IMD) data of the period 1980-2014 reveals that the annual mean temperature of Kashmir valley has increased significantly. Accelerated warming has been observed during 1980-2014, with intense warming in the recent years (2001-2014). During the period 1980-2014, steeper increase, in annual mean maximum temperature than annual mean minimum temperature, has been observed. In addition, mean maximum temperature in plain regions has shown higher rate of increase when compared with mountainous areas. In case of mean minimum temperature, mountainous regions have shown higher rate of increase. Analysis of precipitation data for the same period shows a decreasing trend with mountainous regions having the highest rate of decrease which can be quite hazardous for the fragile mountain environment of the Kashmir valley housing a large number of glaciers.

Geo-spatial analysis of temporal trends of temperature and its extremes over India using daily gridded (1°×1°) temperature data of 1969-2005

NASA Astrophysics Data System (ADS)

Chakraborty, Abhishek; Seshasai, M. V. R.; Rao, S. V. C. Kameswara; Dadhwal, V. K.

2017-10-01

Daily gridded (1°×1°) temperature data (1969-2005) were used to detect spatial patterns of temporal trends of maximum and minimum temperature (monthly and seasonal), growing degree days (GDDs) over the crop-growing season ( kharif, rabi, and zaid) and annual frequencies of temperature extremes over India. The direction and magnitude of trends, at each grid level, were estimated using the Mann-Kendall statistics ( α = 0.05) and further assessed at the homogeneous temperature regions using a field significance test ( α=0.05). General warming trends were observed over India with considerable variations in direction and magnitude over space and time. The spatial extent and the magnitude of the increasing trends of minimum temperature (0.02-0.04 °C year-1) were found to be higher than that of maximum temperature (0.01-0.02 °C year-1) during winter and pre-monsoon seasons. Significant negative trends of minimum temperature were found over eastern India during the monsoon months. Such trends were also observed for the maximum temperature over northern and eastern parts, particularly in the winter month of January. The general warming patterns also changed the thermal environment of the crop-growing season causing significant increase in GDDs during kharif and rabi seasons across India. The warming climate has also caused significant increase in occurrences of hot extremes such as hot days and hot nights, and significant decrease in cold extremes such as cold days and cold nights.

Sensitivity of Last Glacial Maximum climate to uncertainties in tropical and subtropical ocean temperatures

USGS Publications Warehouse

Hostetler, S.; Pisias, N.; Mix, A.

2006-01-01

The faunal and floral gradients that underlie the CLIMAP (1981) sea-surface temperature (SST) reconstructions for the Last Glacial Maximum (LGM) reflect ocean temperature gradients and frontal positions. The transfer functions used to reconstruct SSTs from biologic gradients are biased, however, because at the warmest sites they display inherently low sensitivity in translating fauna to SST and they underestimate SST within the euphotic zones where the pycnocline is strong. Here we assemble available data and apply a statistical approach to adjust for hypothetical biases in the faunal-based SST estimates of LGM temperature. The largest bias adjustments are distributed in the tropics (to address low sensitivity) and subtropics (to address underestimation in the euphotic zones). The resulting SSTs are generally in better agreement than CLIMAP with recent geochemical estimates of glacial-interglacial temperature changes. We conducted a series of model experiments using the GENESIS general atmospheric circulation model to assess the sensitivity of the climate system to our bias-adjusted SSTs. Globally, the new SST field results in a modeled LGM surface-air cooling relative to present of 6.4 ??C (1.9 ??C cooler than that of CLIMAP). Relative to the simulation with CLIMAP SSTs, modeled precipitation over the oceans is reduced by 0.4 mm d-1 (an anomaly -0.4 versus 0.0 mm d-1 for CLIMAP) and increased over land (an anomaly -0.2 versus -0.5 mm d-1 for CLIMAP). Regionally strong responses are induced by changes in SST gradients. Data-model comparisons indicate improvement in agreement relative to CLIMAP, but differences among terrestrial data inferences and simulated moisture and temperature remain. Our SSTs result in positive mass balance over the northern hemisphere ice sheets (primarily through reduced summer ablation), supporting the hypothesis that tropical and subtropical ocean temperatures may have played a role in triggering glacial changes at higher latitudes.

Climate extremes in the Pacific: improving seasonal prediction of tropical cyclones and extreme ocean temperatures to improve resilience

NASA Astrophysics Data System (ADS)

Kuleshov, Y.; Jones, D.; Spillman, C. M.

2012-04-01

Climate change and climate extremes have a major impact on Australia and Pacific Island countries. Of particular concern are tropical cyclones and extreme ocean temperatures, the first being the most destructive events for terrestrial systems, while the latter has the potential to devastate ocean ecosystems through coral bleaching. As a practical response to climate change, under the Pacific-Australia Climate Change Science and Adaptation Planning program (PACCSAP), we are developing enhanced web-based information tools for providing seasonal forecasts for climatic extremes in the Western Pacific. Tropical cyclones are the most destructive weather systems that impact on coastal areas. Interannual variability in the intensity and distribution of tropical cyclones is large, and presently greater than any trends that are ascribable to climate change. In the warming environment, predicting tropical cyclone occurrence based on historical relationships, with predictors such as sea surface temperatures (SSTs) now frequently lying outside of the range of past variability meaning that it is not possible to find historical analogues for the seasonal conditions often faced by Pacific countries. Elevated SSTs are the primary trigger for mass coral bleaching events, which can lead to widespread damage and mortality on reef systems. Degraded coral reefs present many problems, including long-term loss of tourism and potential loss or degradation of fisheries. The monitoring and prediction of thermal stress events enables the support of a range of adaptive and management activities that could improve reef resilience to extreme conditions. Using the climate model POAMA (Predictive Ocean-Atmosphere Model for Australia), we aim to improve accuracy of seasonal forecasts of tropical cyclone activity and extreme SSTs for the regions of Western Pacific. Improved knowledge of extreme climatic events, with the assistance of tailored forecast tools, will help enhance the resilience and

Population trends in Pacific Oceanic sharks and the utility of regulations on shark finning.

PubMed

Clarke, Shelley C; Harley, Shelton J; Hoyle, Simon D; Rice, Joel S

2013-02-01

Accurate assessment of shark population status is essential for conservation but is often constrained by limited and unreliable data. To provide a basis for improved management of shark resources, we analyzed a long-term record of species-specific catches, sizes, and sexes of sharks collected by onboard observers in the western and central Pacific Ocean from 1995 to 2010. Using generalized linear models, we estimated population-status indicators on the basis of catch rate and biological indicators of fishing pressure on the basis of median size to identify trends for blue (Prionace glauca), mako (Isurus spp.), oceanic whitetip (Carcharhinus longimanus), and silky (Carcharhinus falciformis) sharks. Standardized catch rates of longline fleets declined significantly for blue sharks in the North Pacific (by 5% per year [CI 2% to 8%]), for mako sharks in the North Pacific (by 7% per year [CI 3% to 11%]), and for oceanic whitetip sharks in tropical waters (by 17% per year [CI 14% to 20%]). Median lengths of silky and oceanic whitetip sharks decreased significantly in their core habitat, and almost all sampled silky sharks were immature. Our results are consistent with results of analyses of similar data sets. Combined, these results and evidence of targeted fishing for sharks in some regional fisheries heighten concerns for sustainable utilization, particularly for oceanic whitetip and North Pacific blue sharks. Regional regulations that prohibit shark finning (removal of fins and discarding of the carcass) were enacted in 2007 and are in many cases the only form of control on shark catches. However, there is little evidence of a reduction of finning in longline fisheries. In addition, silky and oceanic whitetip sharks are more frequently retained than finned, which suggests that even full implementation of and adherence to a finning prohibition may not substantially reduce mortality rates for these species. We argue that finning prohibitions divert attention from

Sustaining observations of the unsteady ocean circulation.

PubMed

Frajka-Williams, E

2014-09-28

Sustained observations of ocean properties reveal a global warming trend and rising sea levels. These changes have been documented by traditional ship-based measurements of ocean properties, whereas more recent Argo profiling floats and satellite records permit estimates of ocean changes on a near real-time basis. Through these and newer methods of observing the oceans, scientists are moving from quantifying the 'state of the ocean' to monitoring its variability, and distinguishing the physical processes bringing signals of change. In this paper, I give a brief overview of the UK contributions to the physical oceanographic observations, and the role they have played in the wider global observing systems. While temperature and salinity are the primary measurements of physical oceanography, new transbasin mooring arrays also resolve changes in ocean circulation on daily timescales. Emerging technologies permit routine observations at higher-than-ever spatial resolutions. Following this, I then give a personal perspective on the future of sustained observations. New measurement techniques promise exciting discoveries concerning the role of smaller scales and boundary processes in setting the large-scale ocean circulation and the ocean's role in climate. The challenges now facing the scientific community include sustaining critical observations in the case of funding system changes or shifts in government priorities. These long records will enable a determination of the role and response of the ocean to climate change. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Spatial distribution of temperature trends and extremes over Maharashtra and Karnataka States of India

NASA Astrophysics Data System (ADS)

Dhorde, Amit G.; Korade, Mahendra S.; Dhorde, Anargha A.

2017-10-01

Earth surface temperatures are changing worldwide together with the changes in the extreme temperatures. The present study investigates trends and variations of monthly maximum and minimum temperatures and their effects on seasonal fluctuations at different climatological stations of Maharashtra and Karnataka states of India. Trend analysis was performed on annual and seasonal mean maximum temperature (TMAX) and mean minimum temperature (TMIN) for the period 1969 to 2006. During the last 38 years, an increase in annual TMAX and TMIN has occurred. At most of the locations, the increase in TMAX was faster than the TMIN, resulting in an increase in diurnal temperature range. At the same time, annual mean temperature (TM) showed a significant increase over the study area. Percentiles were used to identify extreme temperature indices. An increase in occurrence of warm extremes was observed at southern locations, and cold extremes increased over the central and northeastern part of the study area. Occurrences of cold wave conditions have decreased rapidly compared to heat wave conditions.

Detecting Trends in Tropical Rainfall Characteristics, 1979-2003

NASA Technical Reports Server (NTRS)

Lau, K. M.; Wu, H. T.

2006-01-01

From analyses of blended space-based and ground-based global rainfall data, we found increasing trends in the occurrence of extreme heavy and light rain events, coupled to a decreasing trend in moderate rain events in the tropics during 1979-2003. The trends are consistent with a shift in the large-scale circulation associated with a) a relatively uniform increase in warm rain over the tropical oceans, b) enhanced ice-phase rain over the near-equatorial oceans, and c) reduced mixed-phase rain over the tropical ocean and land regions. Due to the large compensation among different rain categories, the total tropical rainfall trend remained undetectable.

21st Century Trends in Antarctic Temperature and Polar Stratospheric Cloud (PSC) Area in the GEOS Chemistry-Climate Model

NASA Technical Reports Server (NTRS)

Hurwitz, M. M.; Newman, P. A.

2010-01-01

This study examines trends in Antarctic temperature and APSC, a temperature proxy for the area of polar stratospheric clouds, in an ensemble of Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) simulations of the 21st century. A selection of greenhouse gas, ozone-depleting substance, and sea surface temperature scenarios is used to test the trend sensitivity to these parameters. One scenario is used to compare temperature trends in two versions of the GEOS CCM. An extended austral winter season is examined in detail. In May, June, and July, the expected future increase in CO2-related radiative cooling drives temperature trends in the Antarctic lower stratosphere. At 50 hPa, a 1.3 K cooling is expected between 2000 and 2100. Ozone levels increase, despite this robust cooling signal and the consequent increase in APSC, suggesting the enhancement of stratospheric transport in future. In the lower stratosphere, the choice of climate change scenarios does not affect the magnitude of the early winter cooling. Midwinter temperature trends are generally small. In October, APSC trends have the same sign as the prescribed halogen trends. That is, there are negative APSC trends in "grealistic future" simulations, where halogen loading decreases in accordance with the Montreal Protocol and CO2 continues to increase. In these simulations, the speed of ozone recovery is not influenced by either the choice of sea surface temperature and greenhouse gas scenarios or by the model version.

Oxygen-isotope trends and seawater temperature changes across the Late Cambrian Steptoean positive carbon-isotope excursion (SPICE event)

USGS Publications Warehouse

Elrick, M.; Rieboldt, S.; Saltzman, M.; McKay, R.M.

2011-01-01

The globally recognized Late Cambrian Steptoean positive C-isotope excursion (SPICE) is characterized by a 3???-5??? positive ??13C shift spanning <4 m.y. Existing hypotheses suggest that the SPICE represents a widespread ocean anoxic event leading to enhanced burial/preservation of organic matter (Corg) and pyrite. We analyzed ??18O values of apatitic inarticulate brachiopods from three Upper Cambrian successions across Laurentia to evaluate paleotemperatures during the SPICE. ??18O values range from ~12.5??? to 16.5???. Estimated seawater temperatures associated with the SPICE are unreasonably warm, suggesting that the brachiopod ??18O values were altered during early diagenesis. Despite this, all three localities show similar trends with respect to the SPICE ??13C curve, suggesting that the brachiopod apatite preserves a record of relative ??18O and temperature changes. The trends include relatively high ??18O values at the onset of the SPICE, decreasing and lowest values during the main event, and an increase in values at the end of the event. The higher ??18O values during the global extinction at the onset of the SPICE suggests seawater cooling and supports earlier hypotheses of upwelling of cool waters onto the shallow shelf. Decreasing and low ??18O values coincident with the rising limb of the SPICE support the hypothesis that seawater warming and associated reduced thermohaline circulation rates contributed to decreased dissolved O2 concentrations, which enhanced the preservation/burial of Corg causing the positive ??13C shift. ?? 2011 Geological Society of America.

A Southern Ocean variability study using the Argo-based Model for Investigation of the Global Ocean (AMIGO)

NASA Astrophysics Data System (ADS)

Lebedev, Konstantin

2017-04-01

The era of satellite observations of the ocean surface that started at the end of the 20th century and the development of the Argo project in the first years of the 21st century, designed to collect information of the upper 2000 m of the ocean using satellites, provides unique opportunities for continuous monitoring of the Global Ocean state. Starting from 2005, measurements with the Argo floats have been performed over the majority of the World Ocean. In November 2007, the Argo program reached coverage of 3000 simultaneously operating floats (one float in a three-degree square) planned during the development of the program. Currently, 4000 Argo floats autonomously profile the upper 2000-m water column of the ocean from Antarctica to Spitsbergen increasing World Ocean temperature and salinity databases by 12000 profiles per month. This makes it possible to solve problems on reconstructing and monitoring the ocean state on an almost real-time basis, study the ocean dynamics, obtain reasonable estimates of the climatic state of the ocean in the last decade and estimate existing intraclimatic trends. We present the newly developed Argo-Based Model for Investigation of the Global Ocean (AMIGO), which consists of a block for variational interpolation of the profiles of drifting Argo floats to a regular grid and a block for model hydrodynamic adjustment of variationally interpolated fields. Such a method makes it possible to obtain a full set of oceanographic characteristics - temperature, salinity, density, and current velocity - using irregularly located Argo measurements (the principle of the variational interpolation technique entails minimization of the misfit between the interpolated fields defined on the regular grid and irregularly distributed data; hence the optimal solution passes as close to the data as possible). The simulations were performed for the entire globe limited in the north by 85.5° N using 1° grid spacing in both longitude and latitude. At the

Effects of Ocean Acidification and Temperature Increases on the Photosynthesis of Tropical Reef Calcified Macroalgae.

PubMed

Scherner, Fernando; Pereira, Cristiano Macedo; Duarte, Gustavo; Horta, Paulo Antunes; E Castro, Clovis Barreira; Barufi, José Bonomi; Pereira, Sonia Maria Barreto

2016-01-01

Climate change is a global phenomenon that is considered an important threat to marine ecosystems. Ocean acidification and increased seawater temperatures are among the consequences of this phenomenon. The comprehension of the effects of these alterations on marine organisms, in particular on calcified macroalgae, is still modest despite its great importance. There are evidences that macroalgae inhabiting highly variable environments are relatively resilient to such changes. Thus, the aim of this study was to evaluate experimentally the effects of CO2-driven ocean acidification and temperature rises on the photosynthesis of calcified macroalgae inhabiting the intertidal region, a highly variable environment. The experiments were performed in a reef mesocosm in a tropical region on the Brazilian coast, using three species of frondose calcifying macroalgae (Halimeda cuneata, Padina gymnospora, and Tricleocarpa cylindrica) and crustose coralline algae. The acidification experiment consisted of three treatments with pH levels below those occurring in the region (-0.3, -0.6, -0.9). For the temperature experiment, three temperature levels above those occurring naturally in the region (+1, +2, +4°C) were determined. The results of the acidification experiment indicate an increase on the optimum quantum yield by T. cylindrica and a decline of this parameter by coralline algae, although both only occurred at the extreme acidification treatment (-0.9). The energy dissipation mechanisms of these algae were also altered at this extreme condition. Significant effects of the temperature experiment were limited to an enhancement of the photosynthetic performance by H. cuneata although only at a modest temperature increase (+1°C). In general, the results indicate a possible photosynthetic adaptation and/or acclimation of the studied macroalgae to the expected future ocean acidification and temperature rises, as separate factors. Such relative resilience may be a result of the

Effects of Ocean Acidification and Temperature Increases on the Photosynthesis of Tropical Reef Calcified Macroalgae

PubMed Central

Pereira, Cristiano Macedo; Duarte, Gustavo; Horta, Paulo Antunes; e Castro, Clovis Barreira; Barufi, José Bonomi; Pereira, Sonia Maria Barreto

2016-01-01

Climate change is a global phenomenon that is considered an important threat to marine ecosystems. Ocean acidification and increased seawater temperatures are among the consequences of this phenomenon. The comprehension of the effects of these alterations on marine organisms, in particular on calcified macroalgae, is still modest despite its great importance. There are evidences that macroalgae inhabiting highly variable environments are relatively resilient to such changes. Thus, the aim of this study was to evaluate experimentally the effects of CO2-driven ocean acidification and temperature rises on the photosynthesis of calcified macroalgae inhabiting the intertidal region, a highly variable environment. The experiments were performed in a reef mesocosm in a tropical region on the Brazilian coast, using three species of frondose calcifying macroalgae (Halimeda cuneata, Padina gymnospora, and Tricleocarpa cylindrica) and crustose coralline algae. The acidification experiment consisted of three treatments with pH levels below those occurring in the region (-0.3, -0.6, -0.9). For the temperature experiment, three temperature levels above those occurring naturally in the region (+1, +2, +4°C) were determined. The results of the acidification experiment indicate an increase on the optimum quantum yield by T. cylindrica and a decline of this parameter by coralline algae, although both only occurred at the extreme acidification treatment (-0.9). The energy dissipation mechanisms of these algae were also altered at this extreme condition. Significant effects of the temperature experiment were limited to an enhancement of the photosynthetic performance by H. cuneata although only at a modest temperature increase (+1°C). In general, the results indicate a possible photosynthetic adaptation and/or acclimation of the studied macroalgae to the expected future ocean acidification and temperature rises, as separate factors. Such relative resilience may be a result of the

Impact of Langmuir Turbulence on Upper Ocean Response to Hurricane Edouard: Model and Observations

NASA Astrophysics Data System (ADS)

Blair, A.; Ginis, I.; Hara, T.; Ulhorn, E.

2017-12-01

Tropical cyclone intensity is strongly affected by the air-sea heat flux beneath the storm. When strong storm winds enhance upper ocean turbulent mixing and entrainment of colder water from below the thermocline, the resulting sea surface temperature cooling may reduce the heat flux to the storm and weaken the storm. Recent studies suggest that this upper ocean turbulence is strongly affected by different sea states (Langmuir turbulence), which are highly complex and variable in tropical cyclone conditions. In this study, the upper ocean response under Hurricane Edouard (2014) is investigated using a coupled ocean-wave model with and without an explicit sea state dependent Langmuir turbulence parameterization. The results are compared with in situ observations of sea surface temperature and mixed layer depth from AXBTs, as well as satellite sea surface temperature observations. Overall, the model results of mixed layer deepening and sea surface temperature cooling under and behind the storm are consistent with observations. The model results show that the effects of sea state dependent Langmuir turbulence can be significant, particularly on the mixed layer depth evolution. Although available observations are not sufficient to confirm such effects, some observed trends suggest that the sea state dependent parameterization might be more accurate than the traditional (sea state independent) parameterization.

Road structural elements temperature trends diagnostics using sensory system of own design

NASA Astrophysics Data System (ADS)

Dudak, Juraj; Gaspar, Gabriel; Sedivy, Stefan; Pepucha, Lubomir; Florkova, Zuzana

2017-09-01

A considerable funds is spent for the roads maintenance in large areas during the winter. The road maintenance is significantly affected by the temperature change of the road structure. In remote locations may occur a situation, when it is not clear whether the sanding is actually needed because the lack of information on road conditions. In these cases, the actual road conditions are investigated by a personal inspection or by sending out a gritting vehicle. Here, however, is a risk of unnecessary trip the sanding vehicle. This situation is economically and environmentally unfavorable. The proposed system solves the problem of measuring the temperature profile of the road and the utilization of the predictive model to determine the future development trend of temperature. The system was technically designed as a set of sensors to monitor environmental values such as the temperature of the road, ambient temperature, relative air humidity, solar radiation and atmospheric pressure at the measuring point. An important part of the proposal is prediction model which based on the inputs from sensors and historical measurements can, with some probability, predict temperature trends at the measuring point. The proposed system addresses the economic and environmental aspects of winter road maintenance.

Rapid ocean-atmosphere response to Southern Ocean freshening during the last glacial period

NASA Astrophysics Data System (ADS)

Turney, Christian; Jones, Richard; Phipps, Steven; Thomas, Zoë; Hogg, Alan; Kershaw, Peter; Fogwill, Christopher; Palmer, Jonathan; Bronk Ramsey, Christopher; Adolphi, Florian; Muscheler, Raimund; Hughen, Konrad; Staff, Richard; Grosvenor, Mark; Golledge, Nicholas; Rasmussen, Sune; Hutchinson, David; Haberle, Simon; Lorrey, Andrew; Boswijk, Gretel

2017-04-01

Contrasting Greenland and Antarctic temperature trends during the late last glacial period (60,000 to 11,703 years ago) are thought to be driven by imbalances in the rate of formation of North Atlantic and Antarctic Deep Water (the 'bipolar seesaw'), with cooling in the north leading the onset of warming in the south. Some events, however, appear to have occurred independently of changes in deep water formation but still have a southern expression, implying that an alternative mechanism may have driven some global climatic changes during the glacial. Testing these competing hypotheses is challenging given the relatively large uncertainties associated with correlating terrestrial, marine and ice core records of abrupt change. Here we exploit a bidecadally-resolved 14C calibration dataset obtained from New Zealand kauri (Agathis australis) to undertake high-precision alignment of key climate datasets spanning 28,400 to 30,400 years ago. We observe no divergence between terrestrial and marine 14C datasets implying limited impact of freshwater hosing on the Atlantic Meridional Overturning Circulation (AMOC). However, an ice-rafted debris event (SA2) in Southern Ocean waters appears to be associated with dramatic synchronous warming over the North Atlantic and contrasting precipitation patterns across the low latitudes. Using a fully coupled climate system model we undertook an ensemble of transient meltwater simulations and find that a southern salinity anomaly can trigger low-latitude temperature changes through barotropic and baroclinic oceanic waves that are atmospherically propagated globally via a Rossby wave train, consistent with contemporary modelling studies. Our results suggest the Antarctic ice sheets and Southern Ocean dynamics may have contributed to some global climatic changes through rapid ocean-atmospheric teleconnections, with implications for past (and future) change.

Assessment of Air Temperature Trends in the Source Region of Yellow River and Its Sub-Basins, China

NASA Astrophysics Data System (ADS)

Iqbal, Mudassar; Wen, Jun; Wang, Xin; Lan, Yongchao; Tian, Hui; Anjum, Muhammad Naveed; Adnan, Muhammad

2018-02-01

Changes in climatic variables at the sub-basins scale (having different features of land cover) are crucial for planning, development and designing of water resources infrastructure in the context of climate change. Accordingly, to explore the features of climate changes in sub-basins of the Source Region of Yellow River (SRYR), absolute changes and trends of temperature variables, maximum temperature (Tmax), minimum temperature (Tmin), mean temperature (Tavg) and diurnal temperature range (DTR), were analyzed annually and seasonally by using daily observed air temperature dataset from 1965 to 2014. Results showed that annual Tmax, Tmin and Tavg for the SRYR were experiencing warming trends respectively at the rate of 0.28, 0.36 and 0.31°C (10 yr)-1. In comparison with the 1st period (1965-1989), more absolute changes and trends towards increasing were observed during the 2nd period (1990-2014). Apart from Tangnaihai (a low altitude sub-basin), these increasing trends and changes seemed more significant in other basins with highest magnitude during winter. Among sub-basins the increasing trends were more dominant in Huangheyan compared to other sub-basins. The largest increase magnitude of Tmin, 1.24 and 1.18°C (10 yr)-1, occurred in high altitude sub-basins Jimai and Huangheyan, respectively, while the smallest increase magnitude of 0.23°C (10 yr)-1 occurred in a low altitude sub-basin Tangnaihai. The high elevation difference in Tangnaihai probably was the main reason for the less increase in the magnitude of Tmin. In the last decade, smaller magnitude of trend for all temperature variables signified the signal of cooling in the region. Overall, changes of temperature variables had significant spatial and seasonal variations. It implies that seasonal variations of runoff might be greater or different for each sub-basin.

Connecting Ocean Heat Transport Changes from the Midlatitudes to the Arctic Ocean

NASA Astrophysics Data System (ADS)

Hezel, P.; Nummelin, A.; Li, C.

2017-12-01

Under greenhouse warming, climate models simulate a weakening of the Atlantic Meridional Overturning Circulation and the associated ocean heat transport at midlatitudes but an increase in the ocean heat transport to the Arctic Ocean. These opposing trends lead to what could appear to be a discrepancy in the reported ocean contribution to Arctic amplification. This study clarifies how ocean heat transport affects Arctic climate under strong greenhouse warming using a set of the 21st century simulations performed within the Coupled Model Intercomparison Project. The results suggest that a future reduction in subpolar ocean heat loss enhances ocean heat transport to the Arctic Ocean, driving an increase in Arctic Ocean heat content and contributing to the intermodel spread in Arctic amplification. The results caution against extrapolating the forced oceanic signal from the midlatitudes to the Arctic.

Indian summer monsoon rainfall variability during 2014 and 2015 and associated Indo-Pacific upper ocean temperature patterns

NASA Astrophysics Data System (ADS)

Kakatkar, Rashmi; Gnanaseelan, C.; Chowdary, J. S.; Parekh, Anant; Deepa, J. S.

2018-02-01

In this study, factors responsible for the deficit Indian Summer Monsoon (ISM) rainfall in 2014 and 2015 and the ability of Indian Institute of Tropical Meteorology-Global Ocean Data Assimilation System (IITM-GODAS) in representing the oceanic features are examined. IITM-GODAS has been used to provide initial conditions for seasonal forecast in India during 2014 and 2015. The years 2014 and 2015 witnessed deficit ISM rainfall but were evolved from two entirely different preconditions over Pacific. This raises concern over the present understanding of the role of Pacific Ocean on ISM variability. Analysis reveals that the mechanisms associated with the rainfall deficit over the Indian Subcontinent are different in the two years. It is found that remote forcing in summer of 2015 due to El Niño is mostly responsible for the deficit monsoon rainfall through changes in Walker circulation and large-scale subsidence. In the case of the summer of 2014, both local circulation with anomalous anticyclone over central India and intrusion of mid-latitude dry winds from north have contributed for the deficit rainfall. In addition to the above, Tropical Indian Ocean (TIO) sea surface temperature (SST) and remote forcing from Pacific Ocean also modulated the ISM rainfall. It is observed that Pacific SST warming has extended westward in 2014, making it a basin scale warming unlike the strong El Niño year 2015. The eastern equatorial Indian Ocean is anomalously warmer than west in summer of 2014, and vice versa in 2015. These differences in SST in both tropical Pacific and TIO have considerable impact on ISM rainfall in 2014 and 2015. The study reveals that initializing coupled forecast models with proper upper ocean temperature over the Indo-Pacific is therefore essential for improved model forecast. It is important to note that the IITM-GODAS which assimilates only array for real-time geostrophic oceanography (ARGO) temperature and salinity profiles could capture most of the

Response of Antarctic ice shelf melt to SAM trend and possible feedbacks with the ice-dynamics

NASA Astrophysics Data System (ADS)

Donat-Magnin, Marion; Jourdain, Nicolas C.; Gallée, Hubert; Spence, Paul; Cornford, Stephen L.; Le Sommer, Julien; Durand, Gaël

2017-04-01

The observed positive trend in the Southern Annular Mode (SAM) may warm the Southern Ocean sub-surface through decreased Ekman downward pumping. Subsequent change in ice-shelves melt has been suggested to trigger glacier acceleration in West Antarctica. Here we use a regional ocean model configuration of the Amundsen Sea that includes interactive ice-shelf cavities. Our results show that the inclusion of ice-shelves changes the ocean response to the projected SAM trend, i.e. it typically inhibits a part of the SAM-induced subsurface warming. Heat budget analysis has been used to propose responsible mechanisms. Regarding Thwaites and Pine Island, sub ice-shelf melt increases above 400m by approximately 40% for Thwaites and 10% for Pine Island and decreases by up to 10% below in response to ocean temperature changes driven by the projected SAM trend. The melt sensitivity to poleward shifting winds is nonetheless small compared to the sensitivity to an ice-sheet instability, i.e. to a projected change in the shape of ice-shelf cavities. For instance, the sub ice-shelf melt are doubled near the grounding line of some glaciers in response to the largest grounding line retreat projected for 2100. Large increase in basal melt close to the grounding line could largely impact instability and glacier acceleration. Our work suggests the need for including ice shelves into ocean models, and to couple ocean models to ice-sheet models in climate projections.

Impact of the ocean diurnal cycle on the North Atlantic mean sea surface temperatures in a regionally coupled model

NASA Astrophysics Data System (ADS)

Guemas, Virginie; Salas-Mélia, David; Kageyama, Masa; Giordani, Hervé; Voldoire, Aurore

2013-03-01

This study investigates the mechanisms by which the ocean diurnal cycle can affect the ocean mean state in the North Atlantic region. We perform two ocean-atmosphere regionally coupled simulations (20°N-80°N, 80°W-40°E) using the CNRMOM1D ocean model coupled to the ARPEGE4 atmospheric model: one with a 1 h coupling frequency (C1h) and another with a 24 h coupling frequency (C24h). The comparison between both experiments shows that accounting for the ocean diurnal cycle tends to warm up the surface ocean at high latitudes and cool it down in the subtropics during the boreal summer season (June-August). In the subtropics, the leading cause for the formation of the negative surface temperature anomalies is the fact that the nocturnal entrainment heat flux overcompensates the diurnal absorption of solar heat flux. Both in the subtropics and in the high latitudes, the surface temperature anomalies are involved in a positive feedback loop: the cold (warm) surface anomalies favour a decrease (increase) in evaporation, a decrease (increase) in tropospheric humidity, a decrease (increase) in downwelling longwave radiative flux which in turn favours the surface cooling (warming). Furthermore, the decrease in meridional sea surface temperature gradient affects the large-scale atmospheric circulation by a decrease in the zonal mean flow.

Isotopic constraints on the formation of carbonates during low-temperature hydrothermal oceanic crust alteration

NASA Astrophysics Data System (ADS)

Stolper, D. A.; Antonelli, M. A.; Ramos, D. S.; Bender, M. L.; Schrag, D. P.; DePaolo, D. J.; Higgins, J. A.

2016-12-01

Low temperature (<100°C) water-rock reactions in oceanic crust have a potentially large influence on seawater chemical compositions and atmospheric pCO2. Quantification of the conditions (e.g., temperature) of oceanic crust alteration is needed to evaluate its importance for global silicate weathering fluxes. The isotopic and chemical compositions of secondary carbonates in oceanic crust reflect the temperature and chemistry of the circulating fluid and thus are used to reconstruct past conditions of crustal alteration. For example, temperatures are calculated via carbonate δ18O thermometry using measured δ18Ocarb vs. assumed δ18Ofluid. δ18Ofluid is usually assumed to be the seawater value at the time of carbonate formation. We present measured clumped-isotope temperatures (Tclump) and δ18O, δ13C, δ44Ca, and 87Sr/86Sr values of Jurassic carbonates from altered oceanic crust (ODP Site 801). Tclump measured at Caltech ranges from 24-51°C. Calculated δ18Ofluid (based on Tclump and δ18Ocarb) ranges from -0.4‰ (±0.4, 1σ) to -3.5‰ (±0.6). Higher temperatures correlate with lower δ18Ofluid (R2 = 0.75). This suggests that at elevated temperatures, δ18Ofluid was modified away from seawater values, likely via the preferential incorporation of 18O vs. 16O into secondary minerals relative to water. This indicates that δ18Ofluid values of circulating fluids are not necessarily identical to seawater δ18O. Tclump measurements are being replicated at Harvard for further verification. Carbonates with δ13C indicating a seawater C source (δ13C > 0‰) have average δ44Ca (relative to modern seawater) of -0.84‰ (±0.08). This is indistinguishable from igneous rock δ44Ca and suggests that carbonate Ca is derived from igneous Ca released during crustal alteration. Carbonates with δ13C indicating an organic C source (δ13C < -2.5‰) have lower δ44Cacarb (< -1‰). Carbonate 87Sr/86Sr ranges from 0.70742 to 0.70656. Based on the seawater 87Sr/86Sr curve, this

Recent trends in rainfall and temperature over North West India during 1871-2016

NASA Astrophysics Data System (ADS)

Saxena, Rani; Mathur, Prasoon

2018-03-01

Rainfall and temperature are the most important environmental factors influencing crop growth, development, and yield. The northwestern (NW) part of India is one of the main regions of food grain production of the country. It comprises of six meteorological subdivisions (Haryana, Punjab, West Rajasthan, East Rajasthan, Gujarat and Saurashtra, Kutch and Diu). In this study, attempts were made to study variability and trends in rainfall and temperature during 30-year climate normal periods (CN) and 10-year decadal excess or deficit rainfall frequency during the historical period from 1871 to 2016. The Mann-Kendall and Spearman's rank correlation (Spearman's rho) tests were used to determine significance of trends. Least square linear fitting method was adopted to find out the slopes of the trend lines. The long-term mean annual rainfall over North West India is 587.7 mm (standard deviation of 153.0 mm and coefficient of variation 26.0). There was increasing trend in minimum and maximum temperatures during post monsoon season in entire study period and current climate normal period (1991-2016) due to which the sowing of rabi season crops may be delayed and there may be germination problem too. There was a non-significant decreasing trend in rainfall during monsoon season and an increasing trend in rainfall during post monsoon over North West India during entire study period. During current CN5 (1991-2016), all the subdivision (except the Saurashtra region) showed a decreasing trend in rainfall during monsoon season which is a matter of concern for kharif crops and those rabi crops which are grown as rainfed on conserved soil moisture. The decadal annual and seasonal frequencies of excess and deficit years results revealed that the annual total deficit rainfall years (24) exceeded total excess rainfall years (22) in North West India during the entire study period. While during the current decadal period (2011 to 2016), single year was the excess year and 2 years were

Effects of Overshooting Convection on the Tropical Tropopause Layer Temperature Structure and Trends

NASA Astrophysics Data System (ADS)

Ramsay, H.; Sherwood, S. C.; Singh, M.

2017-12-01

A series of idealised cloud-resolving simulations are performed to investigate the impact of spatial/and or temporal inhomogeneity of tropical deep convection (in particular, convective overshoots that penetrate well into the tropical tropopause layer) on upper tropospheric/lower stratospheric (UTLS) temperature structure and trends under surface warming. Two sets of simulations are studied: one in which the sea surface temperature (SST) is increased uniformly, and a second in which convective updrafts are intensified periodically by specifying a diurnally-varying skin temperature. All simulations are run to radiative-convective equilibrium so as to capture the mean-state response at time scales of weeks to months. We discuss the implications of our results for the interpretation of observed and modelled trends in the UTLS, as well as the diurnal cycle of tropical deep convection.

An Inter-calibrated Passive Microwave Brightness Temperature Data Record and Ocean Products

NASA Astrophysics Data System (ADS)

Hilburn, K. A.; Wentz, F. J.

2014-12-01

Inter-calibration of passive microwave sensors has been the subject of on-going activity at Remote Sensing Systems (RSS) since 1974. RSS has produced a brightness temperature TB data record that spans the last 28 years (1987-2014) from inter-calibrated passive microwave sensors on 14 satellites: AMSR-E, AMSR2, GMI, SSMI F08-F15, SSMIS F16-F18, TMI, WindSat. Accompanying the TB record are a suite of ocean products derived from the TBs that provide a 28-year record of wind speed, water vapor, cloud liquid, and rain rate; and 18 years (1997-2014) of sea surface temperatures, corresponding to the period for which 6 and/or 10 GHz measurements are available. Crucial to the inter-calibration and ocean product retrieval are a highly accurate radiative transfer model RTM. The RSS RTM has been continually refined for over 30 years and is arguably the most accurate model in the 1-100 GHz spectrum. The current generation of TB and ocean products, produced using the latest version of the RTM, is called Version-7. The accuracy of the Version-7 inter-calibration is estimated to be 0.1 K, based on inter-satellite comparisons and validation of the ocean products against in situ measurements. The data record produced by RSS has had a significant scientific impact. Over just the last 14 years (2000-2013) RSS data have been used in 743 peer-reviewed journal articles. This is an average of 4.5 peer-reviewed papers published every month made possible with RSS data. Some of the most important scientific contributions made by RSS data have been to the study of the climate. The AR5 Report "Climate Change 2013: The Physical Science Basis" by the Intergovernmental Panel on Climate Change (IPCC), the internationally accepted authority on climate change, references 20 peer-reviewed journal papers from RSS scientists. The report makes direct use of RSS water vapor data, RSS atmospheric temperatures from MSU/AMSU, and 9 other datasets that are derived from RSS data. The RSS TB data record is

Warming Trends and Bleaching Stress of the World’s Coral Reefs 1985–2012

PubMed Central

Heron, Scott F.; Maynard, Jeffrey A.; van Hooidonk, Ruben; Eakin, C. Mark

2016-01-01

Coral reefs across the world’s oceans are in the midst of the longest bleaching event on record (from 2014 to at least 2016). As many of the world’s reefs are remote, there is limited information on how past thermal conditions have influenced reef composition and current stress responses. Using satellite temperature data for 1985–2012, the analysis we present is the first to quantify, for global reef locations, spatial variations in warming trends, thermal stress events and temperature variability at reef-scale (~4 km). Among over 60,000 reef pixels globally, 97% show positive SST trends during the study period with 60% warming significantly. Annual trends exceeded summertime trends at most locations. This indicates that the period of summer-like temperatures has become longer through the record, with a corresponding shortening of the ‘winter’ reprieve from warm temperatures. The frequency of bleaching-level thermal stress increased three-fold between 1985–91 and 2006–12 – a trend climate model projections suggest will continue. The thermal history data products developed enable needed studies relating thermal history to bleaching resistance and community composition. Such analyses can help identify reefs more resilient to thermal stress. PMID:27922080

Detection of trends and break points in temperature: the case of Umbria (Italy) and Guadalquivir Valley (Spain)

NASA Astrophysics Data System (ADS)

Herrera-Grimaldi, Pascual; García-Marín, Amanda; Ayuso-Muñoz, José Luís; Flamini, Alessia; Morbidelli, Renato; Ayuso-Ruíz, José Luís

2018-02-01

The increase of air surface temperature at global scale is a fact with values around 0.85 °C since the late nineteen century. Nevertheless, the increase is not equally distributed all over the world, varying from one region to others. Thus, it becomes interesting to study the evolution of temperature indices for a certain area in order to analyse the existence of climatic trend in it. In this work, monthly temperature time series from two Mediterranean areas are used: the Umbria region in Italy, and the Guadalquivir Valley in southern Spain. For the available stations, six temperature indices (three annual and three monthly) of mean, average maximum and average minimum temperature have been obtained, and the existence of trends has been studied by applying the non-parametric Mann-Kendall test. Both regions show a general increase in all temperature indices, being the pattern of the trends clearer in Spain than in Italy. The Italian area is the only one at which some negative trends are detected. The presence of break points in the temperature series has been also studied by using the non-parametric Pettit test and the parametric standard normal homogeneity test (SNHT), most of which may be due to natural phenomena.

Recent SST trends and Flood Disasters in Brazil

NASA Astrophysics Data System (ADS)

Yamashiki, Y.; Behera, S. K.; Inoue, S.; Netrananda, S.; Silva, R. D.; Takara, K. T.; Yamagata, T.

2010-12-01

We analyzed recent variations in the sea surface temperature (SST) anomalies of Pacific and Atlantic Oceans to understand their roles in extreme discharge of Amazon River Basin. In general, higher than monthly average discharge appears when La Niña condition forms and lower than monthly average discharge appears when El Niño condition forms. We also investigated the relationship between SST anomalies and recent floods in Brazil during the period of 1980-2010. Most severe floods (e.g. 2003 and 2010 Rio de Janeiro-São Paulo Flood) in austral summer occurred when El Niño Modoki appears in the Pacific Ocean. In addition, warm waters in tropical South Atlantic Ocean between American and African Coast also helped the moisture convergence to the affected region. Floods in some other locations (for example, Itaipava flood occurred in Maranhao State in 2008) occurred when a La Niña Modoki appeared in Pacific Ocean. These flood disasters in Brazil associated with climate phenomena may increase due to warmer SST trend under the global warming stress.

Parameterization of typhoon-induced ocean cooling using temperature equation and machine learning algorithms: an example of typhoon Soulik (2013)

NASA Astrophysics Data System (ADS)

Wei, Jun; Jiang, Guo-Qing; Liu, Xin

2017-09-01

This study proposed three algorithms that can potentially be used to provide sea surface temperature (SST) conditions for typhoon prediction models. Different from traditional data assimilation approaches, which provide prescribed initial/boundary conditions, our proposed algorithms aim to resolve a flow-dependent SST feedback between growing typhoons and oceans in the future time. Two of these algorithms are based on linear temperature equations (TE-based), and the other is based on an innovative technique involving machine learning (ML-based). The algorithms are then implemented into a Weather Research and Forecasting model for the simulation of typhoon to assess their effectiveness, and the results show significant improvement in simulated storm intensities by including ocean cooling feedback. The TE-based algorithm I considers wind-induced ocean vertical mixing and upwelling processes only, and thus obtained a synoptic and relatively smooth sea surface temperature cooling. The TE-based algorithm II incorporates not only typhoon winds but also ocean information, and thus resolves more cooling features. The ML-based algorithm is based on a neural network, consisting of multiple layers of input variables and neurons, and produces the best estimate of the cooling structure, in terms of its amplitude and position. Sensitivity analysis indicated that the typhoon-induced ocean cooling is a nonlinear process involving interactions of multiple atmospheric and oceanic variables. Therefore, with an appropriate selection of input variables and neuron sizes, the ML-based algorithm appears to be more efficient in prognosing the typhoon-induced ocean cooling and in predicting typhoon intensity than those algorithms based on linear regression methods.

On the interrelationship between temporal trends in. delta. sup 13 C,. delta. sup 18 O, and. delta. sup 34 S in the world ocean

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoffman, A.; Gruszczynski, M.; Malkowski, K.

1991-05-01

The phenomena of (i) inverse correlation between the oceanic carbon and sulfur isotopic curves, and (ii) covariation between the oceanic carbon and oxygen isotopic curves at all their major excursions appear as paradoxes in the current paradigm of global biogeochemical cycles. These phenomena, however, are fully explicable by a model proposing that the ocean alternates between two general modes: stagnant, stratified, and net autotrophic (overfed) ocean, on the one hand, and vigorously mixed and net heterotrophic (hungry) ocean, on the other. This model is in fact strongly supported by the carbon isotopic evidence. The directions of change in the isotopicmore » ratios of carbon, oxygen, and sulfur should be different in the lower, anoxic box of a stratified ocean than in the upper, oxic box; whereas ocean destratification and mixing of the two boxes should lead to coeval shifts in the oceanic isotopic curves of these elements. The model has far-reaching implications for (i) the causal explanation of both secular trends and major shifts in the oceanic isotopic curves, and (ii) for the application of oxygen isotopic data for paleotemperature and paleoenvironment determinations.« less

Neogene ice volume and ocean temperatures: Insights from infaunal foraminiferal Mg/Ca paleothermometry

NASA Astrophysics Data System (ADS)

Lear, Caroline H.; Coxall, Helen K.; Foster, Gavin L.; Lunt, Daniel J.; Mawbey, Elaine M.; Rosenthal, Yair; Sosdian, Sindia M.; Thomas, Ellen; Wilson, Paul A.

2015-11-01

Antarctic continental-scale glaciation is generally assumed to have initiated at the Eocene-Oligocene Transition, yet its subsequent evolution is poorly constrained. We reconstruct changes in bottom water temperature and global ice volume from 0 to 17 Ma using δ18O in conjunction with Mg/Ca records of the infaunal benthic foraminifer, O. umbonatus from Ocean Drilling Program (ODP) Site 806 (equatorial Pacific; ~2500 m). Considering uncertainties in core top calibrations and sensitivity to seawater Mg/Ca (Mg/Ca)sw, we produce a range of Mg/Ca-temperature-Mg/Casw calibrations. Our favored exponential temperature calibration is Mg/Ca = 0.66 ± 0.08 × Mg/Casw0.27±0.06 × e(0.114±0.02 × BWT) and our favored linear temperature calibration is Mg/Ca = (1.21 ± 0.04 + 0.12 ± 0.004 × BWT (bottom water temperature)) × (Mg/Casw-0.003±0.02) (stated errors are 2 s.e.). The equations are obtained by comparing O. umbonatus Mg/Ca for a Paleocene-Eocene section from Ocean Drilling Program (ODP) Site 690 (Weddell Sea) to δ18O temperatures, calculated assuming ice-free conditions during this peak warmth period of the Cenozoic. This procedure suggests negligible effect of Mg/Casw on the Mg distribution coefficient (DMg). Application of the new equations to the Site 806 record leads to the suggestion that global ice volume was greater than today after the Middle Miocene Climate Transition (~14 Ma). ODP Site 806 bottom waters cooled and freshened as the Pacific zonal sea surface temperature gradient increased, and climate cooled through the Pliocene, prior to the Plio-Pleistocene glaciation of the Northern Hemisphere. The records indicate a decoupling of deep water temperatures and global ice volume, demonstrating the importance of thresholds in the evolution of the Antarctic ice sheet.

Qualitative comparison of air temperature trends based on ncar/ncep reanalysis, model simulations and aerological observations data

NASA Astrophysics Data System (ADS)

Rubinstein, K. G.; Khan, V. M.; Sterin, A. M.

In the present study we discuss two points. The first one is related with applicability of reanalysis data to investigating long-term climate variability. We present results of comparison of long term air temperature trends for the troposphere and the low stratosphere calculated using monthly averaged NCAR/NCEP reanalysis data on one hand and direct rawinsond observations from 443 stations on the other. The trends and other statistical characteristics are calculated for two overlapping time periods, namely 1964 through 1998, and 1979 through 1998. These two intervals were chosen in order to examine the influence of satellite observations on the reanalysis data, given that most satellite data have appeared after 1979. Vertical profiles of air temperature trends are also analyzed using the two types of data for different seasons. A special criterion is applied to evaluate the degree of coincidence by sign between the air temperatures trends derived from the two types of data. Vertical sections of the linear trend averaged over the 10-degrees zones for the both hemispheres are analyzed. It is shown that the two types of data exhibit good coincidence in the terms of the trend sign for the low and middle troposphere and low stratosphere over the areas well covered by the rawinsond observation net. Significant differences of the air temperature trend values are observed near the land surface and in the tropopause layer. The absolute value of the cooling rate of the tropical low stratosphere based on the rawinsond data is larger then that based on the reanalysis data. The presence of a positive trend in the low troposphere in the belt from ˜ 40N to ˜ 70N is evident in the two data sets. A comparative analysis of the trends for the both periods of observation shows that introducing satellite information in the reanalysis data resulted in an increase of the number of stations where the signs of the trend derived from the two sets of data coincide, especially in the

Accelerated warming of the Southern Ocean and its impacts on the hydrological cycle and sea ice.

PubMed

Liu, Jiping; Curry, Judith A

2010-08-24

The observed sea surface temperature in the Southern Ocean shows a substantial warming trend for the second half of the 20th century. Associated with the warming, there has been an enhanced atmospheric hydrological cycle in the Southern Ocean that results in an increase of the Antarctic sea ice for the past three decades through the reduced upward ocean heat transport and increased snowfall. The simulated sea surface temperature variability from two global coupled climate models for the second half of the 20th century is dominated by natural internal variability associated with the Antarctic Oscillation, suggesting that the models' internal variability is too strong, leading to a response to anthropogenic forcing that is too weak. With increased loading of greenhouse gases in the atmosphere through the 21st century, the models show an accelerated warming in the Southern Ocean, and indicate that anthropogenic forcing exceeds natural internal variability. The increased heating from below (ocean) and above (atmosphere) and increased liquid precipitation associated with the enhanced hydrological cycle results in a projected decline of the Antarctic sea ice.

Operational trends in the temperature of a high-pressure microwave powered sulfur lamp

NASA Astrophysics Data System (ADS)

Johnston, C. W.; Jonkers, J.; van der Mullen, J. J. A. M.

2002-10-01

Temperatures have been measured in a high-pressure microwave sulfur lamp using sulfur atomic lines found in the spectrum at 867, 921 and 1045 nm. The absolute intensities were determined for 3, 5 and 7 bar lamps at several input powers, ranging from 400 to 600 W. On average, temperatures are found to be 4.1+/-0.15 kK and increase slightly with increasing pressure and input power. These values and trends agree well with our simulations. However, the power trend is reversed to that demonstrated by the model, which might be an indication that the skin-depth model for the electric field may be incomplete.

A spatiotemporal analysis of U.S. station temperature trends over the last century

NASA Astrophysics Data System (ADS)

Capparelli, V.; Franzke, C.; Vecchio, A.; Freeman, M. P.; Watkins, N. W.; Carbone, V.

2013-07-01

This study presents a nonlinear spatiotemporal analysis of 1167 station temperature records from the United States Historical Climatology Network covering the period from 1898 through 2008. We use the empirical mode decomposition method to extract the generally nonlinear trends of each station. The statistical significance of each trend is assessed against three null models of the background climate variability, represented by stochastic processes of increasing temporal correlation length. We find strong evidence that more than 50% of all stations experienced a significant trend over the last century with respect to all three null models. A spatiotemporal analysis reveals a significant cooling trend in the South-East and significant warming trends in the rest of the contiguous U.S. It also shows that the warming trend appears to have migrated equatorward. This shows the complex spatiotemporal evolution of climate change at local scales.

Global sea level trend in the past century

NASA Technical Reports Server (NTRS)

Gornitz, V.; Lebedeff, S.; Hansen, J.

1982-01-01

Data derived from tide-gauge stations throughout the world indicate that the mean sea level rose by about 12 centimeters in the past century. The sea level change has a high correlation with the trend of global surface air temperature. A large part of the sea level rise can be accounted for in terms of the thermal expansion of the upper layers of the ocean. The results also represent weak indirect evidence for a net melting of the continental ice sheets.

Trend analysis of air temperature and precipitation time series over Greece: 1955-2010

NASA Astrophysics Data System (ADS)

Marougianni, G.; Melas, D.; Kioutsioukis, I.; Feidas, H.; Zanis, P.; Anandranistakis, E.

2012-04-01

In this study, a database of air temperature and precipitation time series from the network of Hellenic National Meteorological Service has been developed in the framework of the project GEOCLIMA, co-financed by the European Union and Greek national funds through the Operational Program "Competitiveness and Entrepreneurship" of the Research Funding Program COOPERATION 2009. Initially, a quality test was applied to the raw data and then missing observations have been imputed with a regularized, spatial-temporal expectation - maximization algorithm to complete the climatic record. Next, a quantile - matching algorithm was applied in order to verify the homogeneity of the data. The processed time series were used for the calculation of temporal annual and seasonal trends of air temperature and precipitation. Monthly maximum and minimum surface air temperature and precipitation means at all available stations in Greece were analyzed for temporal trends and spatial variation patterns for the longest common time period of homogenous data (1955 - 2010), applying the Mann-Kendall test. The majority of the examined stations showed a significant increase in the summer maximum and minimum temperatures; this could be possibly physically linked to the Etesian winds, because of the less frequent expansion of the low over the southeastern Mediterranean. Summer minimum temperatures have been increasing at a faster rate than that of summer maximum temperatures, reflecting an asymmetric change of extreme temperature distributions. Total annual precipitation has been significantly decreased at the stations located in western Greece, as well as in the southeast, while the remaining areas exhibit a non-significant negative trend. This reduction is very likely linked to the positive phase of the NAO that resulted in an increase in the frequency and persistence of anticyclones over the Mediterranean.

Evidence for the role of the Atlantic multidecadal oscillation and the ocean heat uptake in hiatus prediction

NASA Astrophysics Data System (ADS)

Pasini, Antonello; Triacca, Umberto; Attanasio, Alessandro

2017-08-01

The recent hiatus in global temperature at the surface has been analysed by several studies, mainly using global climate models. The common accepted picture is that since the late 1990s, the increase in anthropogenic radiative forcings has been counterbalanced by other factors, e.g., a decrease in natural forcings, augmented ocean heat storage and negative phases of ocean-atmosphere-coupled oscillation patterns. Here, simple vector autoregressive models are used for forecasting the temperature hiatus in the period 2001-2014. This gives new insight into the problem of understanding the ocean contribution (in terms of heat uptake and atmosphere-ocean-coupled oscillations) to the appearance of this recent hiatus. In particular, considering data about the ocean heat content until a depth of 700 m and the Atlantic multidecadal oscillation is necessary for correctly forecasting the hiatus, so catching both trend and interannual variability. Our models also show that the ocean heat uptake is substantially driven by the natural component of the total radiative forcing at a decadal time scale, confining the importance of the anthropogenic influences to a longer range warming of the ocean.

On the Relationship Between Global Land-Ocean Temperature and Various Descriptors of Solar-Geomagnetic Activity and Climate

NASA Technical Reports Server (NTRS)

Wilson, Robert M.

2014-01-01

Examined are sunspot cycle- (SC-) length averages of the annual January-December values of the Global Land-Ocean Temperature Index () in relation to SC-length averages of annual values of various descriptors of solar-geomagnetic activity and climate, incorporating lags of 0-5 yr. For the overall interval SC12-SC23, the is inferred to correlate best against the parameter incorporating lag = 5 yr, where the parameter refers to the resultant aa value having removed that portion of the annual aa average value due to the yearly variation of sunspot number (SSN). The inferred correlation between the and is statistically important at confidence level cl > 99.9%, having a coefficient of linear correlation r = 0.865 and standard error of estimate se = 0.149 degC. Excluding the most recent cycles SC22 and SC23, the inferred correlation is stronger, having r = 0.969 and se = 0.048 degC. With respect to the overall trend in the , which has been upwards towards warmer temperatures since SC12 (1878-1888), solar-geomagnetic activity parameters are now trending downwards (since SC19). For SC20-SC23, in contrast, comparison of the against SC-length averages of the annual value of the Mauna Loa carbon dioxide () index is found to be highly statistically important (cl >> 99.9%), having r = 0.9994 and se = 0.012 degC for lag = 2 yr. On the basis of the inferred preferential linear correlation between the and , the current ongoing SC24 is inferred to have warmer than was seen in SC23 (i.e., >0.526 degC), probably in excess of 0.68 degC (relative to the 1951-1980 base period).

Zonally asymmetric response of the Southern Ocean mixed-layer depth to the Southern Annular Mode

NASA Astrophysics Data System (ADS)

Sallée, J. B.; Speer, K. G.; Rintoul, S. R.

2010-04-01

Interactions between the atmosphere and ocean are mediated by the mixed layer at the ocean surface. The depth of this layer is determined by wind forcing and heating from the atmosphere. Variations in mixed-layer depth affect the rate of exchange between the atmosphere and deeper ocean, the capacity of the ocean to store heat and carbon and the availability of light and nutrients to support the growth of phytoplankton. However, the response of the Southern Ocean mixed layer to changes in the atmosphere is not well known. Here we analyse temperature and salinity data from Argo profiling floats to show that the Southern Annular Mode (SAM), the dominant mode of atmospheric variability in the Southern Hemisphere, leads to large-scale anomalies in mixed-layer depth that are zonally asymmetric. From a simple heat budget of the mixed layer we conclude that meridional winds associated with departures of the SAM from zonal symmetry cause anomalies in heat flux that can, in turn, explain the observed changes of mixed-layer depth and sea surface temperature. Our results suggest that changes in the SAM, including recent and projected trends attributed to human activity, drive variations in Southern Ocean mixed-layer depth, with consequences for air-sea exchange, ocean sequestration of heat and carbon, and biological productivity.

A remote-sensing/GIS application for analysis of sea surface temperature off the western coast of North America

EPA Science Inventory

Recent work reports a warming trend in Pacific Ocean temperatures over the last 50 years. Coastal regions along western North America are particularly sensitive to climatic change, an important indicator of which is sea surface temperature (SST). In situ SST measurements (typica...

Global temperature monitoring from space

NASA Technical Reports Server (NTRS)

Spencer, R. W.

1994-01-01

Global and regional temperature variations in the lower troposphere and lower stratosphere are examined for the period 1979-92 from Microwave Sounder Unit (MSU) data obtained by the Television Infrared Observation Satellite (TIROS)-N series of National Oceanic and Atmospheric Administration (NOAA) operational satellites. In the lower troposphere, globally-averaged temperature variations appear to be dominated by tropical El Nino (warm) and La Nina (cool) events and volcanic eruptions. The Pinatubo volcanic eruption in June 1991 appears to have initiated a cooling trend which persisted through the most recent data analyzed (July, 1992), and largely overwhelmed the warming from the 1991-92 El Nino. The cooling has been stronger in the Northern Hemisphere than in the Southern Hemisphere. The temperature trend over the 13.5 year satellite record is small (+0.03 C) compared to the year-to-year variability (0.2-0.4 C), making detection of any global warming signal fruitless to date. However, the future global warming trend, currently predicted to be around 0.3 C/decade, will be much easier to discern should it develop. The lower stratospheric temperature record is dominated by warm episodes from the Pinatubo eruption and the March 1982 eruption of El Chichon volcano.

Trends in extremes of temperature, dew point, and precipitation from long instrumental series from central Europe

NASA Astrophysics Data System (ADS)

Kürbis, K.; Mudelsee, M.; Tetzlaff, G.; Brázdil, R.

2009-09-01

For the analysis of trends in weather extremes, we introduce a diagnostic index variable, the exceedance product, which combines intensity and frequency of extremes. We separate trends in higher moments from trends in mean or standard deviation and use bootstrap resampling to evaluate statistical significances. The application of the concept of the exceedance product to daily meteorological time series from Potsdam (1893 to 2005) and Prague-Klementinum (1775 to 2004) reveals that extremely cold winters occurred only until the mid-20th century, whereas warm winters show upward trends. These changes were significant in higher moments of the temperature distribution. In contrast, trends in summer temperature extremes (e.g., the 2003 European heatwave) can be explained by linear changes in mean or standard deviation. While precipitation at Potsdam does not show pronounced trends, dew point does exhibit a change from maximum extremes during the 1960s to minimum extremes during the 1970s.

The Need for a Southern Branch Campus of Ocean County College.

ERIC Educational Resources Information Center

Ocean County Coll., Toms River, NJ. Office of Institutional Research.

In 1989, a study was conducted at Ocean County College (OCC) to determine the feasibility of establishing a branch campus in southern Ocean County, New Jersey. Specific factors examined in the study included Ocean County's demographic characteristics (e.g., land area and dispersion, population trends, public transportation, and economic trends);…

Synchronous interhemispheric Holocene climate trends in the tropical Andes

PubMed Central

Polissar, Pratigya J.; Abbott, Mark B.; Wolfe, Alexander P.; Vuille, Mathias; Bezada, Maximiliano

2013-01-01

Holocene variations of tropical moisture balance have been ascribed to orbitally forced changes in solar insolation. If this model is correct, millennial-scale climate evolution should be antiphased between the northern and southern hemispheres, producing humid intervals in one hemisphere matched to aridity in the other. Here we show that Holocene climate trends were largely synchronous and in the same direction in the northern and southern hemisphere outer-tropical Andes, providing little support for the dominant role of insolation forcing in these regions. Today, sea-surface temperatures in the equatorial Pacific Ocean modulate rainfall variability in the outer tropical Andes of both hemispheres, and we suggest that this mechanism was pervasive throughout the Holocene. Our findings imply that oceanic forcing plays a larger role in regional South American climate than previously suspected, and that Pacific sea-surface temperatures have the capacity to induce abrupt and sustained shifts in Andean climate. PMID:23959896

Assessment of surface air temperature over the Arctic Ocean in reanalysis and IPCC AR4 model simulations with IABP/POLES observations

NASA Astrophysics Data System (ADS)

Liu, Jiping; Zhang, Zhanhai; Hu, Yongyun; Chen, Liqi; Dai, Yongjiu; Ren, Xiaobo

2008-05-01

The surface air temperature (SAT) over the Arctic Ocean in reanalyses and global climate model simulations was assessed using the International Arctic Buoy Programme/Polar Exchange at the Sea Surface (IABP/POLES) observations for the period 1979-1999. The reanalyses, including the National Centers for Environmental Prediction Reanalysis II (NCEP2) and European Centre for Medium-Range Weather Forecast 40-year Reanalysis (ERA40), show encouraging agreement with the IABP/POLES observations, although some spatiotemporal discrepancies are noteworthy. The reanalyses have warm annual mean biases and underestimate the observed interannual SAT variability in summer. Additionally, NCEP2 shows an excessive warming trend. Most model simulations (coordinated by the International Panel on Climate Change for its Fourth Assessment Report) reproduce the annual mean, seasonal cycle, and trend of the observed SAT reasonably well, particularly the multi-model ensemble mean. However, large discrepancies are found. Some models have the annual mean SAT biases far exceeding the standard deviation of the observed interannul SAT variability and the across-model standard deviation. Spatially, the largest inter-model variance of the annual mean SAT is found over the North Pole, Greenland Sea, Barents Sea and Baffin Bay. Seasonally, a large spread of the simulated SAT among the models is found in winter. The models show interannual variability and decadal trend of various amplitudes, and can not capture the observed dominant SAT mode variability and cooling trend in winter. Further discussions of the possible attributions to the identified SAT errors for some models suggest that the model's performance in the sea ice simulation is an important factor.

Trend analysis of temperature and precipitation in the Syr Darya Basin in Central Asia

NASA Astrophysics Data System (ADS)

Yao, Junqiang; Chen, Yaning

2015-05-01

By investigating temperature and precipitation data from eight meteorological stations in the Syr Darya Basin (SDB) during 1881-2011 and 1891-2011, we analyzed trends using the Mann-Kendall (MK) test. Our results indicated that there was a notable increasing trend in annual temperature of 0.14 °C/decade ( P < 0.05) and step change points in 1989 ( P < 0.05). Similarly, annual precipitation showed a significant rising trend ( P < 0.001) at a rate of 4.44 mm/decade and step change points in 1991 ( P < 0.05). Overall, temperature and precipitation increases were more rapid in the plains than in the mountain areas. Furthermore, we found that temperature in the SDB region is strongly associated with the Asian Polar Vortex Area Index (APVAI, correlation coefficient: R = -0.701, P < 0.01) rather than with carbon dioxide emissions, especially in the plains area. For precipitation, the correlation coefficient is strongly associated with the Tibet Plateau Index (TPI, R = 0.490, P < 0.01), followed by the Antarctic Oscillation Index (AAOI, R = 0.343, P < 0.01), and the correlations in the plains are higher than those in the mountains. It is anticipated that the results of this study will further the understanding surrounding climate change in the SDB.

140-year subantarctic tree-ring temperature reconstruction reveals tropical forcing of increased Southern Ocean climate variability

NASA Astrophysics Data System (ADS)

Turney, C. S.; Fogwill, C. J.; Palmer, J. G.; VanSebille, E.; Thomas, Z.; McGlone, M.; Richardson, S.; Wilmshurst, J.; Fenwick, P.; Zunz, V.; Goosse, H.; Wilson, K. J.; Carter, L.; Lipson, M.; Jones, R. T.; Harsch, M.; Clark, G.; Marzinelli, E.; Rogers, T.; Rainsley, E.; Ciasto, L.; Waterman, S.; Thomas, E. R.; Visbeck, M.

2017-12-01

Occupying about 14 % of the world's surface, the Southern Ocean plays a fundamental role in ocean and atmosphere circulation, carbon cycling and Antarctic ice-sheet dynamics. Unfortunately, high interannual variability and a dearth of instrumental observations before the 1950s limits our understanding of how marine-atmosphere-ice domains interact on multi-decadal timescales and the impact of anthropogenic forcing. Here we integrate climate-sensitive tree growth with ocean and atmospheric observations on south-west Pacific subantarctic islands that lie at the boundary of polar and subtropical climates (52-54˚S). Our annually resolved temperature reconstruction captures regional change since the 1870s and demonstrates a significant increase in variability from the 1940s, a phenomenon predating the observational record, and coincident with major changes in mammalian and bird populations. Climate reanalysis and modelling show a parallel change in tropical Pacific sea surface temperatures that generate an atmospheric Rossby wave train which propagates across a large part of the Southern Hemisphere during the austral spring and summer. Our results suggest that modern observed high interannual variability was established across the mid-twentieth century, and that the influence of contemporary equatorial Pacific temperatures may now be a permanent feature across the mid- to high latitudes.

Metal-silicate thermochemistry at high temperature - Magma oceans and the 'excess siderophile element' problem of the earth's upper mantle

NASA Technical Reports Server (NTRS)

Capobianco, Christopher J.; Jones, John H.; Drake, Michael J.

1993-01-01

Low-temperature metal-silicate partition coefficients are extrapolated to magma ocean temperatures. If the low-temperature chemistry data is found to be applicable at high temperatures, an important assumption, then the results indicate that high temperature alone cannot account for the excess siderophile element problem of the upper mantle. For most elements, a rise in temperature will result in a modest increase in siderophile behavior if an iron-wuestite redox buffer is paralleled. However, long-range extrapolation of experimental data is hazardous when the data contains even modest experimental errors. For a given element, extrapolated high-temperature partition coefficients can differ by orders of magnitude, even when data from independent studies is consistent within quoted errors. In order to accurately assess siderophile element behavior in a magma ocean, it will be necessary to obtain direct experimental measurements for at least some of the siderophile elements.

Regional aerosol trends over the North Atlantic Ocean since 2002: identifying and attributing using satellite, surface, and model datasets

NASA Astrophysics Data System (ADS)

Jongeward, A.; Li, Z.

2017-12-01

Aerosols from natural and anthropogenic sources can influence atmospheric variability and alter Earth's radiative balance through direct and indirect processes. Recently, policies targeting anthropogenic species (e.g. the Clean Air Act) have seen success in improving air quality. The anthropogenic contributions to the total aerosol loading and its spatiotemporal pattern/trend are anticipated to be altered. In this work the aerosol loading and trend over the North Atlantic Ocean since 2002 are examined, a period of significant change due to anthropogenic emissions control measures within the U.S. Monthly mean data from satellite (MODIS), ground (AERONET, IMPROVE), and model (GOCART, MERRA) sources are employed. Two annual trends in aerosol optical depth (AOD) observed by MODIS are present: a -0.020 decade-1 trend in the mid-latitudes and a 0.015 decade-1 trend in the sub-tropics. Trends in GOCART species AOD reveal anthropogenic (natural) species as the likely driver of the mid-latitude (sub-tropical) trend. AERONET AOD trends confirm negative AOD trends at three upwind sites in the Eastern U.S. and IMPROVE particulate matter (PM) observations identifies the role of decreasing ammonium sulfate in the overall PM decrease. Meanwhile, an increasing AOD trend seen during summertime in the eastern sub-tropics is associated with dust aerosol from North Africa. A dust parameterization from Kaufman et al. (2005) allows for changes in the flux transport across the sub-tropics to be calculated and analyzed. Using MERRA reanalysis fields, it is hypothesized that amplified warming and increases in baroclinic instability over the Saharan desert may lead to increased dust mobilization and export from North Africa to the sub-tropical Atlantic. This study provides updated analysis through 2016.

On the relationship between water vapor over the oceans and sea surface temperature

NASA Technical Reports Server (NTRS)

Stephens, Graeme L.

1990-01-01

Monthly mean precipitable water data obtained from passive microwave radiometry were correlated with the National Meteorological Center (NMC) blended sea surface temperature data. It is shown that the monthly mean water vapor content of the atmosphere above the oceans can generally be prescribed from the sea surface temperature with a standard deviation of 0.36 g/sq cm. The form of the relationship between precipitable water and sea surface temperature in the range T (sub s) greater than 18 C also resembles that predicted from simple arguments based on the Clausius-Clapeyron relationship. The annual cycle of the globally integrated mass of Scanning Multichannel Microwave Radiometer (SMMR) water vapor is shown to differ from analyses of other water vapor data in both phase and amplitude and these differences point to a significant influence of the continents on water vapor. Regional scale analyses of water vapor demonstrate that monthly averaged water vapor data, when contrasted with the bulk sea surface temperature relationship developed in this study, reflect various known characteristics of the time mean large-scale circulation over the oceans. A water vapor parameter is introduced to highlight the effects of large-scale motion on atmospheric water vapor. Based on the magnitude of this parameter, it is shown that the effects of large-scale flow on precipitable water vapor are regionally dependent, but for the most part, the influence of circulation is generally less than about + or - 20 percent of the seasonal mean.

On the relationship between water vapor over the oceans and sea surface temperature

NASA Technical Reports Server (NTRS)

Stephens, Graeme L.

1989-01-01

Monthly mean precipitable water data obtained from passive microwave radiometry were correlated with the National Meteorological Center (NMC) blended sea surface temperature data. It is shown that the monthly mean water vapor content of the atmosphere above the oceans can generally be prescribed from the sea surface temperature with a standard deviation of 0.36 g/sq cm. The form of the relationship between precipitable water and sea surface temperature in the range T(sub s) greater than 18 C also resembles that predicted from simple arguments based on the Clausius-Clapeyron relationship. The annual cycle of the globally integrated mass of Scanning Multichannel Microwave Radiometer (SMMR) water vapor is shown to differ from analyses of other water vapor data in both phase and amplitude and these differences point to a significant influence of the continents on water vapor. Regional scale analyses of water vapor demonstrate that monthly averaged water vapor data, when contrasted with the bulk sea surface temperature relationship developed in this study, reflect various known characteristics of the time mean large-scale circulation over the oceans. A water vapor parameter is introduced to highlight the effects of large-scale motion on atmospheric water vapor. Based on the magnitude of this parameter, it is shown that the effects of large-scale flow on precipitable water vapor are regionally dependent, but for the most part, the influence of circulation is generally less than about + or - 20 percent of the seasonal mean.

Recent surface temperature trends in the interior of East Antarctica from borehole firn temperature measurements and geophysical inverse methods

USGS Publications Warehouse

Muto, A.; Scambos, T.A.; Steffen, K.; Slater, A.G.; Clow, G.D.

2011-01-01

We use measured firn temperatures down to depths of 80 to 90 m at four locations in the interior of Dronning Maud Land, East Antarctica to derive surface temperature histories spanning the past few decades using two different inverse methods. We find that the mean surface temperatures near the ice divide (the highest-elevation ridge of East Antarctic Ice Sheet) have increased approximately 1 to 1.5 K within the past ???50 years, although the onset and rate of this warming vary by site. Histories at two locations, NUS07-5 (78.65S, 35.64E) and NUS07-7 (82.07S, 54.89E), suggest that the majority of this warming took place in the past one or two decades. Slight cooling to no change was indicated at one location, NUS08-5 (82.63S, 17.87E), off the divide near the Recovery Lakes region. In the most recent decade, inversion results indicate both cooler and warmer periods at different sites due to high interannual variability and relatively high resolution of the inverted surface temperature histories. The overall results of our analysis fit a pattern of recent climate trends emerging from several sources of the Antarctic temperature reconstructions: there is a contrast in surface temperature trends possibly related to altitude in this part of East Antarctica. Copyright 2011 by the American Geophysical Union.

Law sets up oceans commission

NASA Astrophysics Data System (ADS)

Showstack, Randy

In an anticipated move, U.S. President Bill Clinton on August 7 signed into law the Oceans Act of 2000.The bipartisan legislation, which takes effect on January 20,2001, establishes a commission on ocean policy to examine federal ocean policy and environmental and economic trends affecting oceans and coasts.The act—which grew out of a call issued by Clinton at the National Oceans Conference in Monterey, California in 1998—requires the commission to submit recommendations to Congress and the president within 18 months of its appointment, and for the President to submit proposals to Congress about the use and stewardship of ocean and coastal resources.

Methodology and results of calculating central California surface temperature trends: Evidence of human-induced climate change?

USGS Publications Warehouse

Christy, J.R.; Norris, W.B.; Redmond, K.; Gallo, K.P.

2006-01-01

A procedure is described to construct time series of regional surface temperatures and is then applied to interior central California stations to test the hypothesis that century-scale trend differences between irrigated and nonirrigated regions may be identified. The procedure requires documentation of every point in time at which a discontinuity in a station record may have occurred through (a) the examination of metadata forms (e.g., station moves) and (b) simple statistical tests. From this "homogeneous segments" of temperature records for each station are defined. Biases are determined for each segment relative to all others through a method employing mathematical graph theory. The debiased segments are then merged, forming a complete regional time series. Time series of daily maximum and minimum temperatures for stations in the irrigated San Joaquin Valley (Valley) and nearby nonirrigated Sierra Nevada (Sierra) were generated for 1910-2003. Results show that twentieth-century Valley minimum temperatures are warming at a highly significant rate in all seasons, being greatest in summer and fall (> +0.25??C decade-1). The Valley trend of annual mean temperatures is +0.07?? ?? 0.07??C decade-1. Sierra summer and fall minimum temperatures appear to be cooling, but at a less significant rate, while the trend of annual mean Sierra temperatures is an unremarkable -0.02?? ?? 0.10??C decade-1. A working hypothesis is that the relative positive trends in Valley minus Sierra minima (>0.4??C decade-1 for summer and fall) are related to the altered surface environment brought about by the growth of irrigated agriculture, essentially changing a high-albedo desert into a darker, moister, vegetated plain. ?? 2006 American Meteorological Society.

Strengthening of Ocean Heat Uptake Efficiency Associated with the Recent Climate Hiatus

NASA Technical Reports Server (NTRS)

Watanabe, Masahiro; Kamae, Youichi; Yoshimori, Masakazu; Oka, Akira; Sato, Makiko; Ishii, Masayoshi; Mochizuki, Takashi; Kimoto, Masahide

2013-01-01

The rate of increase of global-mean surface air temperature (SAT(sub g)) has apparently slowed during the last decade. We investigated the extent to which state-of-the-art general circulation models (GCMs) can capture this hiatus period by using multimodel ensembles of historical climate simulations. While the SAT(sub g) linear trend for the last decade is not captured by their ensemble means regardless of differences in model generation and external forcing, it is barely represented by an 11-member ensemble of a GCM, suggesting an internal origin of the hiatus associated with active heat uptake by the oceans. Besides, we found opposite changes in ocean heat uptake efficiency (k), weakening in models and strengthening in nature, which explain why the models tend to overestimate the SAT(sub g) trend. The weakening of k commonly found in GCMs seems to be an inevitable response of the climate system to global warming, suggesting the recovery from hiatus in coming decades.

Enhanced deep ocean ventilation and oxygenation with global warming

NASA Astrophysics Data System (ADS)

Froelicher, T. L.; Jaccard, S.; Dunne, J. P.; Paynter, D.; Gruber, N.

2014-12-01

Twenty-first century coupled climate model simulations, observations from the recent past, and theoretical arguments suggest a consistent trend towards warmer ocean temperatures and fresher polar surface oceans in response to increased radiative forcing resulting in increased upper ocean stratification and reduced ventilation and oxygenation of the deep ocean. Paleo-proxy records of the warming at the end of the last ice age, however, suggests a different outcome, namely a better ventilated and oxygenated deep ocean with global warming. Here we use a four thousand year global warming simulation from a comprehensive Earth System Model (GFDL ESM2M) to show that this conundrum is a consequence of different rates of warming and that the deep ocean is actually better ventilated and oxygenated in a future warmer equilibrated climate consistent with paleo-proxy records. The enhanced deep ocean ventilation in the Southern Ocean occurs in spite of increased positive surface buoyancy fluxes and a constancy of the Southern Hemisphere westerly winds - circumstances that would otherwise be expected to lead to a reduction in deep ocean ventilation. This ventilation recovery occurs through a global scale interaction of the Atlantic Meridional Overturning Circulation undergoing a multi-centennial recovery after an initial century of transient decrease and transports salinity-rich waters inform the subtropical surface ocean to the Southern Ocean interior on multi-century timescales. The subsequent upwelling of salinity-rich waters in the Southern Ocean strips away the freshwater cap that maintains vertical stability and increases open ocean convection and the formation of Antarctic Bottom Waters. As a result, the global ocean oxygen content and the nutrient supply from the deep ocean to the surface are higher in a warmer ocean. The implications for past and future changes in ocean heat and carbon storage will be discussed.

Trend of annual temperature and frequency of extreme events in the MATOPIBA region of Brazil

NASA Astrophysics Data System (ADS)

Salvador, Mozar de A.; de Brito, J. I. B.

2017-06-01

During the 1980s, a new agricultural frontier arouse in Brazil, which occupied part of the states of Maranhão, Tocantins, Piauí, and Bahia. Currently, this new frontier is known as the MATOPIBA region. The region went through intense transformations in its social and environmental characteristics, with the emergence of extensive areas of intensive agriculture and large herds. The purpose of this research was to study the climatic variabilities of temperature in the MATOPIBA region through extreme climate indexes of ClimAp tool. Data from 11 weather stations were analyzed for yearly air temperature (maximum and minimum) in the period of 1970 to 2012. To verify the trend in the series, we used methods of linear regression analysis and Kendall-tau test. The annual analysis of maximum and minimum temperatures and of the temperature extremes indexes showed a strong positive trend in practically every series (with p value less than 0.05). These results indicated that the region went through to a significant heating process in the last 3 decades. The indices of extreme also showed a significant positive trend in most of the analyzed stations, indicating a higher frequency of warm days during the year.