Sea Surface Temperature Off Research Articles

Sea Surface Warming and its Implications for Harmful Algal Blooms off Oman

The analysis of the sea surface temperature (SST) data for the period from 1961 to 2010, showed the SST regime changes off Oman on different temporal scales. A rapid warming phase is conspicuous in the SST off Muscat and off Masirah along Oman after 1984. The shifts in the SST occurred several times on shorter time scales prior to 1984 but a notable shift in the SST occurred after 1984 when the mean annual SST increased by 0.53℃ off Masirah and by 0.32℃ off Muscat. The amplitude and period of heating/cooling are smaller and shorter off Muscat compared to Masirah with increasing summer warming and decreasing winter cooling. The multivariate ENSO index (MEI) and the annual mean SST at the study locations showed better correlation (R 2 =0.3) with April-May MEI compared to the other months. The highs and lows of SST at both the locations responded with stronger El Nino and La Nina events respectively. The frequency of harmful algal bloom (HAB) events off Oman closely followed the warming and cooling patterns of the sea surface. The frequency of HAB events increased with increasing SST during present decade (2001~2010). The increase in toxic or potentially harmful HAB events may be the consequence of upper ocean stratification forced by increasing SST.

Pleistocene water cycle and eastern boundary current processes along the California continental margin

[1] Coastal marine sediments contain mixtures of terrestrial and marine paleoclimate proxies that record how the coastal water cycle has behaved over long time frames. We explore a 600 kyr marine record from ODP Site 1018, located due west of Santa Cruz, California, to identify coastal wet and dry periods and to associate them with oceanographic processes. Wet periods in central California, identified by increased tree pollen relative to pollen from grasslands and scrublands, are found on every major deglaciation in the last 600 kyr. Sea surface temperature (SST) data were collected for the last two deglaciations. Wet periods are associated with a rapid rise in SST off central California. SST gradients along the California margin and changes in biogenic deposition show that wet periods in central California are associated with a weakening of the California Current and weakened coastal upwelling. High carbonate production suggests that there was significant curl-of-wind stress upwelling offshore. We propose that wet periods in central California are associated with a meteorological connection to the tropical Pacific and weakened southward flow in the California Current that shunted temperate Pacific water northward into the Alaska gyre. We do not observe evidence for a south-shifted westerly storm track at the last glacial maximum but find that wet periods are diachronous along the California margin. The wettest period around the Santa Barbara Basin peaked at 16 ka, preceding the wet peak in central and northern California by 4 kyr.

Extratropical forcing of Sahel aridity during Heinrich stadials

In order to investigate a possible link between tropical Northeast (NE) Atlantic sea‐surface temperature (SST), Atlantic meridional overturning circulation (AMOC), and drought in the Sahel during the past 44 thousand years (kyr) we used alkenone paleothermometry and δ13C of C. wuellerstorfi of a marine sediment core from the continental slope off Senegal. Our data show periods of low SST and reduced AMOC that coincided with drought in the Sahel during North Atlantic Heinrich stadials (HS). The coldest period was HS1 (ca. 15–18 kyr before present, BP) when SST decreased by more than 2°C. Moreover, the SST off Senegal lagged variations in Sahel aridity, which is in agreement with results from a freshwater hosing experiment. We conclude that variations in tropical NE Atlantic SST were not the initial trigger of millennial‐scale Sahel droughts of the past 44 kyr. Instead, it is thought that these droughts were induced by substantial coolings of the extratropical North Atlantic.

Bulk organic geochemistry of sediments from Puyehue Lake and its watershed (Chile, 40°S): Implications for paleoenvironmental reconstructions

Since the last deglaciation, the mid-latitudes of the southern Hemisphere have undergone considerable environmental changes. In order to better understand the response of continental ecosystems to paleoclimate changes in southern South America, we investigated the sedimentary record of Puyehue Lake, located in the western piedmont of the Andes in South–Central Chile (40°S). We analyzed the elemental (C, N) and stable isotopic (δ 13C, δ 15N) composition of the sedimentary organic matter preserved in the lake and its watershed to estimate the relative changes in the sources of sedimentary organic carbon through space and time. The geochemical signature of the aquatic and terrestrial end-members was determined on samples of lake particulate organic matter (N/C: 0.130) and Holocene paleosols (N/C: 0.069), respectively. A simple mixing equation based on the N/C ratio of these end-members was then used to estimate the fraction of terrestrial carbon (ƒ T) preserved in the lake sediments. Our approach was validated using surface sediment samples, which show a strong relation between ƒ T and distance to the main rivers and to the shore. We further applied this equation to an 11.22 m long sediment core to reconstruct paleoenvironmental changes in Puyehue Lake and its watershed during the last 17.9 kyr. Our data provide evidence for a first warming pulse at 17.3 cal kyr BP, which triggered a rapid increase in lake diatom productivity, lagging the start of a similar increase in sea surface temperature (SST) off Chile by 1500 years. This delay is best explained by the presence of a large glacier in the lake watershed, which delayed the response time of the terrestrial proxies and limited the concomitant expansion of the vegetation in the lake watershed (low ƒ T). A second warming pulse at 12.8 cal kyr BP is inferred from an increase in lake productivity and a major expansion of the vegetation in the lake watershed, demonstrating that the Puyehue glacier had considerably retreated from the watershed. This second warming pulse is synchronous with a 2 °C increase in SST off the coast of Chile, and its timing corresponds to the beginning of the Younger Dryas Chronozone. These results contribute to the mounting evidence that the climate in the mid-latitudes of the southern Hemisphere was warming during the Younger Dryas Chronozone, in agreement with the bipolar see-saw hypothesis.

Expressions of 1976–1977 and 1988–1989 Regime Shifts in Sea-Surface Temperature off Southern California and Hawai‘i1

Sea-surface temperatures off southern California from Scripps Pier and from Koko Head, Hawai‘i, were examined to determine what impact regime shifts that occurred in 1976–1977 and 1988–1989 had on environmental conditions at each location. Cumulative sums were employed to enhance the detection process. The cumulative sum time histories revealed major turning points at both locations at the time of the 1976–1977 event. At both locations, increases in temperature were indicated, consistent with the phase change in the Pacific Decadal Oscillation that took place at that time. The cumulative sums also indicated major turning points at both locations during the 1988–1989 event. A new procedure called the method of expanding means was employed to determine the long-term impact of these events. By comparing means before and after a given event it is possible to observe the magnitude of the change and to what extent it is sustained. For the 1976–1977 regime shift, temperatures increased rapidly and remained consistently higher, by ∼1°C for 2–3 yr at Scripps Pier. This increase occurred over a period of approximately 7 months and accounts for more than half of the total warming that has occurred at that location since 1920. At Koko Head, a similar response was observed with a sustained increase of approximately 0.5°C. The oceanic response to the 1988–1989 event was quite different. At Scripps Pier, temperatures before and after this event did not show any tendency to converge to significantly different values out to periods of 2–3 yr. At Koko Head, mean temperatures did converge to slightly different values after 1 yr, with mean values being consistently lower after this event (∼−0.4°C). It was shown that in some cases changes associated with these events could be identified in the original data, but without the help of cumulative sums, it is usually not possible to make a clear distinction between changes of interest and other sources of variability. Finally, decorrelation time scales for the records at both locations were estimated and found to be on the order of a year, implying spatial scales that are at least synoptic (tens to hundreds of kilometers).

Interannual Variability of Sea Surface Temperature off Java and Sumatra in a Global GCM*

Abstract Using results from the Simple Ocean Data Assimilation (SODA), this study assesses the mixed layer heat budget to identify the mechanisms that control the interannual variation of sea surface temperature (SST) off Java and Sumatra. The analysis indicates that during the positive Indian Ocean Dipole (IOD) years, cold SST anomalies are phase locked with the season cycle. They may exceed −3°C near the coast of Sumatra and extend as far westward as 80°E along the equator. The depth of the thermocline has a prominent influence on the generation and maintenance of SST anomalies. In the normal years, cooling by upwelling–entrainment is largely counterbalanced by warming due to horizontal advection. In the cooling episode of IOD events, coastal upwelling–entrainment is enhanced, and as a result of mixed layer shoaling, the barrier layer no longer exists, so that the effect of upwelling–entrainment can easily reach the surface mixed layer. Horizontal advection spreads the cold anomaly to the interior tropical Indian Ocean. Near the coast of Java, the northern branch of an anomalous anticyclonic circulation spreads the cold anomaly to the west near the equator. Both the anomalous advection and the enhanced, wind-driven upwelling generate the cold SST anomaly of the positive IOD. At the end of the cooling episode, the enhanced surface thermal forcing overbalances the cooling effect by upwelling/entrainment, and leads to a warming in SST off Java and Sumatra.

Marine environmental conditions in the SW Indian Ocean and sympathetic trends of coastal fish catch

This study considers marine environmental factors driving fluctuations in coastal fish catch in the SW Indian Ocean using FAO data. A consistent oscillation of catch is found for Mauritius, Madagascar, Reunion and the Comoros, and is shown to be related to a widespread change in marine environmental conditions that prevails during the preceding year that include the following: - An upper ridge of high pressure is present to the south of Madagascar where SSTs are above normal; - Southerly winds are stronger to the east of Madagascar; westerly winds are strengthened in the monsoon zone around 5- 10 S; - Dry weather prevails in a NW-SE band across Madagascar and the adjacent island nations; and, - Sea surface temperatures (SST) off Angola increase well in advance. Further work is needed to compare marine environmental signals that could emerge from locally sourced fish catch data and those reported here with the FAO time series. Keywords : Indian Ocean, climate change, fisheries West Indian Ocean Journal of Marine Science Vol. 4 (2) 2005: pp. 199-206

Influence of upwelling, subsurface stratification, and heat fluxes on coastal sea surface temperature off southwestern New Caledonia

Strong cooling events off the western barrier reef of New Caledonia have been recently observed and attributed to wind‐driven coastal upwelling. A simple one‐dimensional model based on a heat budget in the mixed laxer is developed and calibrated to explain the daily variations of sea surface temperature (SST) observed at a coastal station off southwestern New Caledonia from 1992 to 2005. This model takes into account the daily wind‐forced vertical advection and air‐sea heat fluxes, as well as seasonal variations of the subsurface temperature stratification. It can explain a large part of the daily SST variations and helps to quantify the relative contribution of the main vertical processes involved in these variations. The model shows that upwelling is the dominant process at daily timescale, and its SST signature is strongly modulated by the seasonal variations of the subsurface stratification. The surface heat fluxes have a smaller influence than upwelling on daily SST variations. Coastal chlorophyll a concentration increases during upwelling events.

Interannual Rainfall Extremes over Southwest Western Australia Linked to Indian Ocean Climate Variability

Abstract Interannual rainfall extremes over southwest Western Australia (SWWA) are examined using observations, reanalysis data, and a long-term natural integration of the global coupled climate system. The authors reveal a characteristic dipole pattern of Indian Ocean sea surface temperature (SST) anomalies during extreme rainfall years, remarkably consistent between the reanalysis fields and the coupled climate model but different from most previous definitions of SST dipoles in the region. In particular, the dipole exhibits peak amplitudes in the eastern Indian Ocean adjacent to the west coast of Australia. During dry years, anomalously cool waters appear in the tropical/subtropical eastern Indian Ocean, adjacent to a region of unusually warm water in the subtropics off SWWA. This dipole of anomalous SST seesaws in sign between dry and wet years and appears to occur in phase with a large-scale reorganization of winds over the tropical/subtropical Indian Ocean. The wind field alters SST via anomalous Ekman transport in the tropical Indian Ocean and via anomalous air–sea heat fluxes in the subtropics. The winds also change the large-scale advection of moisture onto the SWWA coast. At the basin scale, the anomalous wind field can be interpreted as an acceleration (deceleration) of the Indian Ocean climatological mean anticyclone during dry (wet) years. In addition, dry (wet) years see a strengthening (weakening) and coinciding southward (northward) shift of the subpolar westerlies, which results in a similar southward (northward) shift of the rain-bearing fronts associated with the subpolar front. A link is also noted between extreme rainfall years and the Indian Ocean Dipole (IOD). Namely, in some years the IOD acts to reinforce the eastern tropical pole of SST described above, and to strengthen wind anomalies along the northern flank of the Indian Ocean anticyclone. In this manner, both tropical and extratropical processes in the Indian Ocean generate SST and wind anomalies off SWWA, which lead to moisture transport and rainfall extremes in the region. An analysis of the seasonal evolution of the climate extremes reveals a progressive amplification of anomalies in SST and atmospheric circulation toward a wintertime maximum, coinciding with the season of highest SWWA rainfall. The anomalies in SST can appear as early as the summertime months, however, which may have important implications for predictability of SWWA rainfall extremes.

Paleoproductivity evolution off central Chile from the Last Glacial Maximum to the Early Holocene

A geochemical and paleontological reconstruction of paleoproductivity, upwelling intensity and sea surface temperature (SST) off central Chile at 35°S (GeoB3359-3) reveals marked changes from the Last Glacial Maximum (LGM) through the Early Holocene. Surface-water productivity was determined by the interaction between the atmospheric (the Southern Westerlies) and oceanographic (the Antarctic Circumpolar Current, ACC) systems from the LGM through early Termination I (TI). The northward shift of the climate zones during the LGM brought the ACC, as the main macronutrient source, closer to the GeoB3359-3, SST lowered, and surface water productivity and accumulation rates of biogenic components enhanced. With the poleward return of the Southern Westerlies and the ACC, the subtropical high-pressure system became the dominant atmospheric component southward till 35°S during the late TI and Early Holocene and caused surface water productivity to increase through enhanced upwelling.

Impact of interannual rainfall anomalies on Indian Ocean salinity and temperature variability

A nonlinear reduced gravity model with four active layers and mixed layer physics is used to investigate how precipitation anomalies affect salinity and temperature variability in the Indian Ocean. In one experiment the model is forced by observations of monthly varying winds and rainfall for the period 1980–2000. In another it is forced by the same winds and climatological rainfall. Comparison between the two experiments is focused on the 1992–2000 period, during which rainfall variations attain extrema in the southeastern Indian Ocean with two deficits close to zero in 1994 and 1997 and a maximum of 16 mm/d in 1998. Rainfall anomalies significantly affect model sea surface salinity (SSS), but SSS is also highly governed by winds. Indeed, SSS is at its absolute minimum in 1994 despite the local rainfall deficit. Sea surface temperature (SST) is strongly affected along the equator east of 80°E and along Indonesia where the mixed and the barrier layers become thin in 1994 and 1997. There the precipitation deficits affect SST primarily by entraining more subsurface water to the surface. In 1994 the subsurface waters are anomalously cool because of eastward advection of colder water from the west. In 1997 they are so because of northward advection of water cooled by coastal upwelling farther south. The precipitation excess does not affect SST because the temperature difference between the mixed layer and the barrier layer is very little then. Including interannual rainfall anomalies makes SST off Sumatra colder in 1994 and 1997, in much better agreement with observations.

Comment on “modelling the inception of the Patagonian icesheet”

A geochemical and paleontological reconstruction of paleoproductivity, upwelling intensity and sea surface temperature (SST) off central Chile at 35°S (GeoB3359-3) reveals marked changes from the Last Glacial Maximum (LGM) through the Early Holocene. Surface-water productivity was determined by the interaction between the atmospheric (the Southern Westerlies) and oceanographic (the Antarctic Circumpolar Current, ACC) systems from the LGM through early Termination I (TI). The northward shift of the climate zones during the LGM brought the ACC, as the main macronutrient source, closer to the GeoB3359-3, SST lowered, and surface water productivity and accumulation rates of biogenic components enhanced. With the poleward return of the Southern Westerlies and the ACC, the subtropical high-pressure system became the dominant atmospheric component southward till 35°S during the late TI and Early Holocene and caused surface water productivity to increase through enhanced upwelling.

Millennial-scale oceanic climate variability off the Western Iberian margin during the last two glacial periods

High-resolution palaeoclimate records recovered from the Iberian margin in core MD95-2040 exhibit large fluctuations in oceanographic conditions over the last 190 ka. Large-scale cooling of the surface ocean is indicated by the presence of the polar planktonic foraminifer Neogloboquadrina pachyderma (sinistral), and in some instances the occurrence of ice-rafted debris (IRD). Ice-rafting episodes were prevalent in both of the last two glacials with greater intensity in Stages 2 through 4, than in Stage 6. The six youngest Heinrich events are well defined during the last glacial but detrital carbonate is absent from Heinrich layers HL6, HL5 and HL3. Dansgaard–Oeschger stadial-equivalent sub-millennial IRD deposition events have been detected, in particular during Stage 3, allowing a good match with the cooling displayed in the Greenland ice core (GISP2). Sea-surface temperature off Portugal in Stage 6 was in general warmer than during the last glacial, pointing towards a weaker southward influence of polar water masses. Ice rafting occurred mainly in mid-MIS (Marine Isotope Stage) 6 (between 173 and 153 kyr) as a group of poorly differentiated, short-duration quasi-continuous events, mainly marked by the high abundance of sinistral N. pachyderma. Differences exist in IRD composition relative to the last glacial, with a reduced Canadian-derived detrital carbonate component, combined with an important contribution of volcanic particles. The lower magnitude and higher frequency of these events suggest that the higher temperatures would have induced iceberg waning closer to the source areas.

Local and remote forcing of sea surface temperature in the coastal upwelling system off Chile

An analysis is presented of records of sea surface temperature (SST), sea level and winds collected during the period 1991–1995 along the coast of northern and central Chile (sea level also from the Peru coast in 1991–1994), and of SST from remote sensing during the austral summers of 1991 and 1992 off northern Chile. Large, interannual fluctuations of SST and sea level off northern Chile are linked to vertical displacements of the equatorial thermocline during El Niño‐La Niña events. In the intraseasonal, 50‐day band, SST and sea level are intimately related all along the coast, whereby SST anomalies lag sea level perturbations by about 12 days. Such sea level fluctuations are due to free, coastal‐trapped waves, ultimately forced via equatorial Kelvin waves by 50‐day wind events in the western and central tropical Pacific. These results and those of the remote sensing analysis suggest significant remote forcing of SST fluctuations in the coastal zone off Chile by the action of the coastal‐trapped waves. Off central Chile, SST is also related to local wind stress in the intraseasonal band. Simulations with a simple, local, wind‐driven upwelling/entrainment model capture rather well observed synoptic and intraseasonal oscillations of SST there. Off northern Chile, however, this simple model is not successful in simulating observed SST. An attempt to include effects of coastal‐trapped waves into this simple, one‐dimensional model did not improve model fit to data at either location. An explanation for the apparent strong influence of these waves on SST along this coast should therefore be sought in other effects not considered by this model such as cross‐shelf and alongshore advection.

The climate of North America and adjacent ocean waters ca. 6 ka

The climate of North America and the adjacent ocean at 6000 BP was estimated using five independent approaches. Using pollen data, the terrestrial climate was estimated by the movement of ecozone boundaries and by the method of modern analogues. Both analyses indicate warmer temperatures in the western Great Lakes area and the northern Great Plains. A model of Sphagnum-dominated peatland initiation, when forced by Canadian Climate Model 6 ka output projected a cooler and (or) wetter climate for continental western North America. Contrary to this, a reconstruction of the distribution of Sphagnum-dominated peatlands in western Canada indicates that they were located north of their modern distribution, suggesting warmer and (or) drier conditions at 6000 BP. This interpretation is strengthened by observations of lower lake levels at 6000 BP in western Canada. This drier climate may have been associated with warmer conditions as indicated by the quantitative climate reconstructions. In general, eastern North America was drier, while western North America was warmer and drier at 6 ka compared to the present. A model of vegetation and carbon storage, when forced using 6 ka Canadian Climate Model and pollen-based climate reconstructions, showed an increase in area covered by boreal forest, extending north and south of the present location. This was not, however, verified by the fossil data. Additionally, the model showed little total change in carbon storage at 6 ka in the terrestrial biosphere. Estimated sea surface temperatures off eastern Canada suggest warmer surface waters at 6 ka, in agreement with reconstructions based on terrestrial records from the eastern seaboard.

Seasonal and interannual variability of currents and temperature off central Chile

Results are reported for continuous, 6 year records of current and temperature from a continental slope station at 30°S off Chile. These observations for November 1991 to November 1997 span the moderate, weak, and strong El Niño events of 1991–1992, 1994, and 1997 and the La Niña event of 1995–1996. Results for current and temperature are analyzed together with observations of wind along the South American coast from the ERS‐1 and ‐2 satellite scatterometers, wind from a local coastal site, sea level from northern and central Chile, sea surface temperature anomalies from the South Pacific region, and traditional El Niño indices. Mean poleward flow of 12.8 cm s−1 was observed for the 6 year period in the core of the Peru‐Chile Undercurrent (220 m). Mean flow in the depth range of Antarctic Intermediate Water (750 m) was equatorward at 1.1 cm s−1. Intraseasonal‐scale variability associated with coastal trapped waves was weaker during the austral winter: greatest during El Niño events and weakest during the La Niña event. Winds adjacent to the coast showed a strong annual cycle with a southward progression of maximum equatorward (upwelling favorable) winds. Alongshore flow over the slope exhibited strong semiannual and weaker annual variations. Poleward flow in the undercurrent was strongest in the austral spring and fall and weakest in the winter. Near the bottom (750 m), seasonal‐scale variability was less intense but led that higher up in the water column (220 m) by ∼1 month. Strong interannual variability of alongshore current and temperature was found at all depths over the slope, whereby changes at depth led changes higher up. A rapid warming event was observed at the end of 1996‐beginning of 1997 over the slope. This event, also seen in sea level and sea surface temperature off Chile, led El Niño indices by several months and may be best explained by local wind anomalies coupled to atmospheric teleconnections from the western tropical Pacific at the onset of El Niño. Some aspects of our current and temperature observations are consistent with results from eastern boundary current models. Our results indicate that both ocean and atmosphere pathways from the equatorial Pacific contribute significantly to interannual‐scale variability of alongshore flow and thermocline depth off Chile.

Links between Annual Variations of Peruvian Stratocumulus Clouds and of SST in the Eastern Equatorial Pacific

The hypothesis that Peruvian stratocumulus play an important role on both the annual mean and annual variations of sea surface temperature (SST) in the eastern equatorial Pacific is examined. The problem is addressed by performing sensitivity experiments using the University of California, Los Angeles, coupled atmosphere–ocean GCM with different idealized temporal variations of stratocumulus in a region along the coast of Peru. The results obtained are consistent with the notion that Peruvian stratocumulus are a key component of the interhemispherically asymmetric features that characterize the annual mean climate of the eastern equatorial Pacific, including the cold SSTs off Peru and the absence of a southern ITCZ. The principal new finding of this study is that the annual variations (i.e., deviations from the annual mean) of Peruvian stratocumulus are linked to the differences between the amplitude, duration, and westward propagation of the warm and cold phases of the equatorial cold tongue. In the model’s context, only if the prescribed annual variations of Peruvian stratocumulus have the same phase as the observed variations are those differences successfully captured. The impact of Peruvian stratocumulus on equatorial SST involves “dynamical” and “thermal” effects. The former develop through an enhancement of the northerly component of the surface wind from the Peruvian coast to the equator. The thermal effects develop through the special relationships between SST and surface evaporation over the equatorial cold tongue, which contributes to extend the cold phase until the end of the year. A successful portrayal of this behavior requires a realistic simulation of the annual variations of surface wind over the equatorial cold tongue.

South-East Atlantic warm events: composite evolution and consequences for southern African climate

Tropical South-Eastern Atlantic sea surface temperature (SST) fluctuations in the period 1951-1991 are investigated in the context of regional climate impacts. Departures of rotated principal component 1 of late summer outgoing longwave radiation (OLR) reflect a dipole between the south-western plateau (Kalahari) and the Angolan coast, which explains 47% of total field variance over southern Africa. The principal component scores are correlated with SST off Angola and with other tropical regions exhibiting global El Niño responses. The spatial loading implies diminished convective rainfall over the Kalahari when tropical SST to the northwest of Angola is > 0,7°C (∼1 standard deviation) above normal, for example in 1984. SST fluctuations in discrete areas of the tropical South-Eastern Atlantic are examined. The annual cycle is dominated by an inverse relationship between SST and pressure, with a maximum (minimum for pressure) in the months February to April. South-easterly trade winds are prevalent throughout the year, but are considerably weaker in the "bight" of Angola. Composite warm events in the late summers of 1963, 1973, 1984 and 1988 are analysed using normalized departures. The results indicate that oceanic warm events are locally generated in the region 0–10°S, 0–15°E, following a reduction in trade winds locally and to the west in the preceding year. Maximum SST is attained typically in March, following a sudden increase after the previous November. The composite precursors suggest that empirical predictability of South-Eastern Atlantic warm events is limited. Relationships between the 1995 event and drought over the Kalahari are discussed. Further research on sea levels, thermocline depth and currents, coupled to numerical modelling, could offer improved insights.

Relationship between measurements of hake biomass and sea surface temperature off southern Namibia

A good relationship between the variability in measurements of Cape hake Merluccius capensis biomass during winter and summer swept-area research surveys and sea surface temperature off southern Namibia for the years 1983–1990 is presented. The results call into question the hypothesis that hake density is related to biomass and imply that abnormally warm summers could support higher catches, regardless of the state of the stock. A hypothesis that anomalous warm conditions could induce hake to concentrate closer to the sea bed, making them more susceptible to bottom trawling, is presented.

Satellite monitoring of sea surface temperatures off China

Satellite measurements of global sea surface temperatures (SST) have been made since 1982 using the multi-channel radiometers (AVHRR) on NOAA polar orbiting satellites. A four year data set was accumulated at daily intervals and a spatial resolution of about 100 kilometers on an interactive computer system. The time lapse evaluation of the data revealed variations of the SST which were related to coastal and equatorial upwelling events as well as to the pronounced equatorial warming associated with the 1982–1983 El Nino. In the present study, satellite time series are used to describe the annual variability of the SST at selected locations along the coast of China, the Yellow Sea, the Sea of Japan and the Equatorial Indian and Pacific Oceans. Further study of the SST off China using higher resolution satellite data are also described.