Inflow Of Warm Water Research Articles

Observations of the Antarctic Slope Current in the Southeastern Weddell Sea: A Bottom‐Enhanced Current and Its Seasonal Variability

AbstractThe Antarctic Slope Front and the associated Antarctic Slope Current dynamically regulate the exchanges of heat across the continental shelf break around Antarctica. Where the front is weak, relatively warm deep waters reach the ice shelf cavities, contributing to basal melting and ultimately affecting sea level rise. Here, we present new 2017–2021 records from two moorings deployed on the upper continental slope (530 and 738 m depth) just upstream of the Filchner Trough in the southeastern Weddell Sea. The structure and seasonal variability of the frontal system in this region, central to the inflow of warm water toward the large Filchner‐Ronne Ice Shelf, is previously undescribed. We use the records to describe the mean state and the seasonal variability of the regional hydrography and the southern part of the Antarctic Slope Current. We find that (a) the current is, contrary to previous assumptions, bottom‐enhanced, (b) the isotherms slope upwards toward the shelf break, and more so for warmer isotherms, and (c) the monthly mean thermocline depth is shallowest in February‐March and deepest in May‐June while (d) the current is strongest in April‐June. On monthly timescales, we show that (e) positive temperature anomalies of the de‐seasoned records are associated with weaker‐than‐average currents. We propose that the upward‐sloping isotherms are linked to the local topography and conservation of potential vorticity. Our results contribute to the understanding of how warm ocean waters propagate southward and potentially affect basal melt rates at the Filchner‐Ronne Ice Shelf.

Upwelling-induced inflow pulses in a tropical bay during mid-summer drought

Bahía Santa Elena is a tropical bay located in the northern Pacific region of Costa Rica. This region experiences a period of reduced precipitation from July to August, known as mid-summer drought, induced by the intensification of northeastern winds from the Caribbean Low-Level Jet. Intensification of upwelling-favorable winds can cool surface waters adjacent to the bay, leading to a reduction in water temperatures within the bay, that alters the biological dynamics of coastal habitats. This study aims to analyze upwelling-induced inflow pulses in Bahía Santa Elena during mid-summer drought, focusing on the cooling effect of intensified upwelling-favorable winds and the subsequent warm water inflows following wind relaxation. We conducted two measuring campaigns from June to July in 2021 and in 2022. The first campaign consisted of a single acoustic Doppler current profiler (ADCP) moored inside the bay. The second campaign consisted of two mooring deployments: an ADCP with a thermistor chain inside the bay and an ADCP installed at the inlet. Each campaign presented five distinct events of upwelled water inflows into the bay promoted by an offshore Ekman transport. Upwelling-favorable wind peaks were followed by a decrease in temperature of the water column. When the upwelling-favorable wind relaxed, a warm water pulse entered the bay. These events are expected to play an important role in biological processes within tropical bays adjacent to upwelling zones during mid-summer drought.

Assessment of the Impact of Pacific Inflow on Sea Surface Temperature Prior to the Freeze-Up Period over the Bering Sea

Warm water inflow from the Northeast Pacific has always been considered a crucial factor in early winter freeze-up in the Bering Sea. There is a strong correlation between changes in sea surface temperature (SST) on the eastern Bering Sea shelf and sea ice area in December. However, there is still limited research on the impact of Pacific inflow on SST on the eastern Bering Sea shelf, resulting in insufficient measurements of the impact of Pacific inflow on early freeze-up. In this article, the definition of marine heatwaves (MHW) is used to extract warm events (with a threshold of the 70th percentile) and cold events (with a threshold of the 30th percentile) from the eastern Bering Sea shelf in November. Self-organizing map (SOM) technology is utilized to classify extracted cold and warm events and the mixed-layer heat budget is ultimately used to explore the factors that generate and maintain these cold and warm events. Between 1993 and 2021, a total of 12 warm and 12 cold events are extracted and their cumulative intensity is found to be strongly correlated with the interannual variation in SST by 99.8%, indicating that these warm and cold events are capable of characterizing the interannual variation in SST. Among the 12 warm events, 9 of them can be attributed to abnormal warming of seawater before November and only 3 events are attributed to warm water inflow from the Northeast Pacific. During the development of warm events, there are only two events in which the warm inflow from the Northeast Pacific has a more profound regulatory effect on warm events in November. Moreover, both generation and regulatory factors of cold events are the net air–sea heat flux. Statistics indicate that the warm water inflow from the Northeast Pacific has a limited effect on SST on the eastern Bering Sea shelf during the early freeze-up period. Changes in local SST are more influenced by the residual heat before November and by local net air–sea heat flux. However, we highlight that long-term ocean heatwaves occurring in the Northeast Pacific can enlarge the residual heat of seawater in the eastern Bering Sea shelf before November, thereby impacting early freeze-up. The frequency of such events has significantly increased in the past decade, causing notable changes in the climate and ecosystem of the Bering Sea. Therefore, it is crucial to continue closely monitoring the occurrence and development of such events in the future.

Seasonal variation in microplankton communities in Suttsu, Hokkaido, northern Japan, from 2020 to 2022

Southwestern Hokkaido faces intricate physiological and chemical changes. Subsequently, changes in lower trophic levels are of concern, but fully understanding the relationship between microplankton and hydrography in this region is required. To examine the relationship between the microplankton community (diatoms, dinoflagellates, ciliates, and euglenoids) and environmental factors in Suttsu, Hokkaido, water samples were collected at 4–15-day intervals from August 2020 to August 2022 at Yokoma Port. Diatoms were dominant in the study area, with an apparent seasonal change in species composition. Lower phytoplankton cell density was observed in the second year than in the first year during autumn and winter because of low temperatures and light intensity in the second year. A significant decrease in the number of attached diatoms (Navicula spp.) was observed during the winter of the second year, possibly due to calm conditions (low tide and wind speed), which prevent the detachment of weakly attached species. Large blooms of euglenoids (Eutreptiella gymnastica and E. marina) in April and May were caused by the exclusive use of nutrients from the inflow of river water during the snowmelt season. Warm-water species sporadically occurred, suggesting their transportation by the Tsushima Warm Current. Temperature, nutrients, and light intensity primarily control microplankton communities, which vary seasonally. These findings led to the prediction of lower trophic levels due to the impact of warm water inflow.

On the drivers of regime shifts in the Antarctic marginal seas, exemplified by the Weddell Sea

Abstract. Recent studies have found evidence for a potential future tipping point, when the density of Antarctic continental shelf waters, specifically in the southern Weddell Sea, will allow for the onshore flow of warm waters of open ocean origin. A cold-to-warm regime shift in the adjacent ice shelf cavities entails a strong enhancement of ice shelf basal melt rates and could trigger instabilities in the ice sheet. From a suite of numerical experiments, aimed to force such a regime shift on the continental shelf, we identified the density balance between the shelf waters formed by sea ice production and the warmer water at the shelf break as the defining element of a tipping into a warm state. In our experiments, this process is reversible but there is evidence for hysteresis behaviour. Using HadCM3 20th-century output as atmospheric forcing, the resulting state of the Filchner–Ronne cavity depends on the initial state. In contrast, ERA Interim forcing pushes even a warm-initialized cavity into a cold state, i.e. it pushes the system back across the reversal threshold to the cold side. However, it turns out that for forcing data perturbations of a realistic magnitude, a unique and universal recipe for triggering a regime shift in Antarctic marginal seas was not found; instead, various ocean states can lead to an intrusion of off-shelf waters onto the continental shelf and into the cavities. Whether or not any given forcing or perturbation yields a density imbalance and thus allows for the inflow of warm water depends on the complex interplay between bottom topography, mean ocean state, sea ice processes, and atmospheric conditions.

Sea ice variability in the North Atlantic subpolar gyre throughout the Last Interglacial

The Last Interglacial period, Marine Isotope Stage 5e (MIS 5e ∼116–128 ka), is thought to have had a warmer, but less stable climate than the present interglacial. One key factor that has the potential to influence the ocean and climate is sea ice, but its presence and extent throughout MIS 5e is poorly constrained. Here we reconstruct the sea surface hydrography and sea ice variability in the Labrador Sea, a region influenced by the subpolar gyre (SPG) and where deep water formation occurs, in order to evaluate the potential of sea ice to drive or amplify ocean variability. We analysed biomarkers (highly branched isoprenoids, HBIs, and sterols), dinoflagellate cyst assemblages and stable oxygen isotopes from the late stages of MIS 6, throughout MIS 5e, into MIS 5d. Our results show that the late glacial MIS 6 was likely characterised by a thick multiyear sea ice cover. During the first phase of MIS 5e, the hydrography was highly variable. The initial 1500 years (128–126.5 ka) were characterised by the presence of a seasonal Marginal Ice Zone (MIZ) accompanied by subsurface warmth. As the sea ice retreated, cool, likely polar-sourced water dominated the surface and subsurface ocean (126.5–124 ka), until an abrupt surge of sea ice marked the final pulse of the remnants of the deglaciation. The second half of MIS 5e (124–116 ka) was characterised by a persistent inflow of warm water, only interrupted by incursions of cold water as summer insolation declined. Seasonal sea ice returned to the Eirik Drift during MIS 5d. We infer that sea ice variability throughout MIS 5e was coupled with the variability of the SPG. Especially the location of a proximal MIZ to the Labrador Sea convection region could have been important for SPG dynamics. In addition, the presence of sea ice at the transitions into and out of MIS 5e could point to its important role in modulating and enhancing the magnitude and coherence of climate signals at major climatic transitions.

Relative contributions of local heat storage and ocean heat transport to cold‐season Arctic Ocean surface energy fluxes in CMIP6 models

AbstractThe Arctic near‐surface air temperature increases most strongly during the cold season, and ocean heat storage has often been cited as a crucial component in linking the ice‐albedo radiative feedback, which is active in summer, and near‐surface air temperature increase in winter, when the lapse rate feedback contributes to Arctic warming. Here, we first estimate how much local heat storage and ocean heat transport contribute to net surface energy fluxes on a seasonal scale in CMIP6 models. We then compare contributions in a base state under weak anthropogenic forcing to a near‐present‐day state in which significant Arctic amplification is simulated. Our analysis indicates that, in a few regions, ocean heat transport plays a larger role for cold‐season net surface energy fluxes compared with local heat storage. Analyzing differences between past and near‐present‐day conditions suggests that the lapse rate feedback, which mainly acts during the cold season in warm water inflow regions, may be more strongly influenced than previously thought by increased ocean heat transport from lower latitudes.

The potential for stabilizing Amundsen Sea glaciers via underwater curtains.

Rapid sea level rise due to an ice sheet collapse has the potential to be extremely damaging the coastal communities and infrastructure. Blocking deep warm water with thin flexible buoyant underwater curtains may reduce melting of buttressing ice shelves and thereby slow the rate of sea level rise. Here, we use new multibeam bathymetric datasets, combined with a cost-benefit model, to evaluate potential curtain routes in the Amundsen Sea. We organize potential curtain routes along a "difficulty ladder" representing an implementation pathway that might be followed as technological capabilities improve. The first curtain blocks a single narrow (5 km) submarine choke point that represents the primary warm water inflow route towards western Thwaites Glacier, the most vulnerable part of the most vulnerable glacier in Antarctica. Later curtains cross larger and deeper swaths of seabed, thus increasing their cost, while also protecting more of the ice sheet, increasing their benefit. In our simple cost-benefit analysis, all of the curtain routes achieve their peak value at target blocking depths between 500 and 550 m. The favorable cost-benefit ratios of these curtain routes, along with the trans-generational and societal equity of preserving the ice sheets near their present state, argue for increased research into buoyant curtains as a means of ice sheet preservation, including high-resolution fluid-structural and oceanographic modeling of deep water flow over and through the curtains, and coupled ice-ocean modeling of the dynamic response of the ice sheet.

Impact of Cyclonic Wind Anomalies Caused by Massive Winter Sea Ice Retreat in the Barents Sea on Atlantic Water Transport Toward the Arctic: A Model Study

AbstractThe Arctic is warming much faster than the global average. This is known as Arctic Amplification and is caused by feedbacks in the local climate system. In this study, we explore a previously proposed hypothesis that an associated wind feedback in the Barents Sea could play an important role by increasing the warm water inflow into the Barents Sea. We find that the strong recent decrease in Barents Sea winter sea ice cover causes enhanced ocean‐atmosphere heat flux and a local air temperature increase, thus a reduction in sea level pressure and a local cyclonic wind anomaly with eastward winds in the Barents Sea Opening. By investigating various reanalysis products and performing high‐resolution perturbation experiments with the ocean and sea ice model FESOM2.1, we studied the impact of cyclonic atmospheric circulation changes on the warm Atlantic Water import into the Arctic via the Barents Sea and Fram Strait. We found that the observed wind changes do not significantly affect the warm water transport into the Barents Sea, which rejects the wind‐feedback hypothesis. At the same time, the cyclonic wind anomalies in the Barents Sea increase the amount of Atlantic Water recirculating westwards in Fram Strait by a downslope shift of the West Spitsbergen Current, and thus reduce Atlantic Water reaching the Arctic basin via Fram Strait. The resulting warm‐water anomaly in the Greenland Sea Gyre drives a local anticyclonic circulation anomaly.

Inter-decadal climate variability induces differential ice response along Pacific-facing West Antarctica

West Antarctica has experienced dramatic ice losses contributing to global sea-level rise in recent decades, particularly from Pine Island and Thwaites glaciers. Although these ice losses manifest an ongoing Marine Ice Sheet Instability, projections of their future rate are confounded by limited observations along West Antarctica’s coastal perimeter with respect to how the pace of retreat can be modulated by variations in climate forcing. Here, we derive a comprehensive, 12-year record of glacier retreat around West Antarctica’s Pacific-facing margin and compare this dataset to contemporaneous estimates of ice flow, mass loss, the state of the Southern Ocean and the atmosphere. Between 2003 and 2015, rates of glacier retreat and acceleration were extensive along the Bellingshausen Sea coastline, but slowed along the Amundsen Sea. We attribute this to an interdecadal suppression of westerly winds in the Amundsen Sea, which reduced warm water inflow to the Amundsen Sea Embayment. Our results provide direct observations that the pace, magnitude and extent of ice destabilization around West Antarctica vary by location, with the Amundsen Sea response most sensitive to interdecadal atmosphere-ocean variability. Thus, model projections accounting for regionally resolved ice-ocean-atmosphere interactions will be important for predicting accurately the short-term evolution of the Antarctic Ice Sheet.

Exploring a Warm Water Inflow Below an Antarctic Ice Shelf

Researchers guided an autonomous underwater submarine to capture the first direct observations of a warm water current flowing in below the Filchner-Ronne Ice Shelf in Antarctica.

Observations of Modified Warm Deep Water Beneath Ronne Ice Shelf, Antarctica, From an Autonomous Underwater Vehicle

AbstractFilchner‐Ronne Ice Shelf (FRIS) is the world's largest ice shelf by volume. It helps regulate Antarctica's contribution to global sea level rise, and water mass transformations within the sub‐ice‐shelf cavity produce globally important dense water masses. Rates of ice shelf basal melting are relatively low, however, as the production of cold (−1.9°C) and dense High Salinity Shelf Water over the Weddell Sea continental shelf isolates the ice shelf from large‐scale inflow of warm water. Nevertheless, a narrow inflow of relatively warm (−1.4°C) Modified Warm Deep Water (MWDW) that hugs the western flank of Berkner Bank is observed to reach Ronne Ice Front, although the processes governing its circulation and fate remain uncertain. Here we present the first observations taken within the ice shelf cavity along this warm water inflow using the Autosub Long Range autonomous underwater vehicle. We observe a core of MWDW with a south‐westward velocity of 4 cm s−1 that reaches at least 18 km into the sub‐ice cavity. The hydrographic properties are spatially heterogeneous, giving rise to temporal variability that is driven by tidal advection. The highest rates of turbulent dissipation are associated with the warmest MWDW, with the vertical eddy diffusivity reaching 10−4 m2 s−1 where the water column is fully turbulent. Mixing efficiency is close to the canonical value of 0.2. Modeling studies suggest MWDW may become the dominant water mass beneath FRIS in our changing climate, providing strong motivation to understand more fully the dynamics of this MWDW inflow.

Seasonal variability of ocean circulation near the Dotson Ice Shelf, Antarctica

Recent rapid thinning of West Antarctic ice shelves are believed to be caused by intrusions of warm deep water that induce basal melting and seaward meltwater export. This study uses data from three bottom-mounted mooring arrays to show seasonal variability and local forcing for the currents moving into and out of the Dotson ice shelf cavity. A southward flow of warm, salty water had maximum current velocities along the eastern channel slope, while northward outflows of freshened ice shelf meltwater spread at intermediate depth above the western slope. The inflow correlated with the local ocean surface stress curl. At the western slope, meltwater outflows followed the warm influx along the eastern slope with a ~2–3 month delay. Ocean circulation near Dotson Ice Shelf, affected by sea ice distribution and wind, appears to significantly control the inflow of warm water and subsequent ice shelf melting on seasonal time-scales.

Widespread Grounding Line Retreat of Totten Glacier, East Antarctica, Over the 21st Century

AbstractTotten Glacier (TG), the primary ice discharger of East Antarctica, contains 3.85 m sea level rise equivalent (SLRe) ice mass and has displayed ocean‐driven dynamic change since at least the early 2000s. We project TG's evolution through 2100 in an asynchronously coupled ice‐ocean model, forced at the ocean boundaries with anomalies in CMIP6 projected temperature, salinity, and velocity. Consistent with previous studies, the Antarctic Slope Current continues to modulate warm water inflow toward TG in future simulations. Warm water (−0.5 – C) accesses TG's sub‐ice shelf cavity through depressions along the eastern ice front, driving sustained retreat of TG's eastern grounding zone that cannot be captured in uncoupled models. In high emission scenarios, warm water overcomes topographic barriers and dislodges TG's southern grounding zone around 2070, increasing the rate of grounded ice loss 3.5‐fold (10–35 Gt/yr) and resulting in a total 4.20 mm SLRe loss by 2100.

Orbital-scale vegetation-ocean-atmosphere linkages in western Japan during the last 550 ka based on a pollen record from the IODP site U1427 in the Japan Sea

Climate and vegetation in Japan are strongly influenced by the East Asian Monsoon (EAM) and the ocean environment of the Japan Sea. This study discusses the findings from a new pollen record from Integrated Ocean Drilling Program Site U1427, situated off the northern coast of the Honshu Island in western Japan, which allows for direct comparisons with other oceanographic proxies from this area. Our findings demonstrate the orbital-scale vegetation changes in this area and their land-ocean-atmosphere linkages during the last 550 ka. During surface-water freshening events in the Japan Sea, likely associated with colder water temperatures caused by the very low eustatic sea levels and the consequent isolation from the surrounding seas during the full-glacial periods, cold-cool conifer forests became dominant under the extremely dry pseudo-continental conditions in the Japanese islands. In contrast, temperate broadleaf forests increased rapidly when the surface-freshening events ended and a weak inflow of warm water began at the onset of deglaciation, in addition to the rapid atmospheric climate warming during termination periods. During the intermediate periods between the full interglacial to the full-glacial, the Tp ratio (pollen temperature index) increased in association with the summer insolation maxima caused by the Earth's precession cycle that coincide with Chinese stalagmite negative δ18O peaks, whereas Cryptomeria pollen abundance (high-precipitation index) increased in association with the winter insolation maxima. Those orbital-scale vegetation fluctuations were attributed to the changes in seasonal temperature and precipitation patterns, where were influenced by the EAM changes that were associated with seasonal insolation changes around the Japanese archipelago. Cryptomeria forests likely developed under cool and wet conditions throughout a year with low seasonal contrasts, whereas deciduous broadleaf forests increased under condition of high seasonality with cool summers and colder, drier winters. Alternating fluctuations between the Tp ratio and Cryptomeria pollen abundance following the insolation changes were typically observed after MIS 9 and are thought to have been affected by the periodicity shift in the EAM fluctuations across the Mid-Brunhes Event.

Atmospheric Rivers, Warm Air Intrusions, and Surface Radiation Balance in the Amundsen Sea Embayment

AbstractOver recent decades the primary climatic forcing on the ice shelves in the Amundsen Sea Embayment (ASE) has been the influx of warm water into sub‐ice‐shelf ocean cavities. By contrast, the contribution of a globally warming atmosphere has been negligible but may play a more significant role in the future. Warm, moist air intrusions from the ocean onto the ice sheet surface play an essential role in the surface energy budget and constitute the primary driver for surface melting in West Antarctica. This study employs observations from automatic weather stations deployed on the Pine Island Glacier and numerical model outputs from the Antarctic Mesoscale Prediction System to investigate warm air intrusion (WAI) events and examine their impacts on surface glacier melt in the ASE. A deep low‐pressure center over the Amundsen/Ross Seas and a blocking ridge over the southeast Pacific created favorable conditions for developing an atmospheric river that directs warm and moist air toward the ASE. An analysis of meteorological observations through 2013–2014 shows that 2013 received two times higher frequency WAI events than 2014. 2013 year coincides with more substantial pressure gradients in the western Ross Sea and the eastern Amundsen Sea. The February and March 2013 WAI events induce about 3 days of surface melting over the Pine Island Glacier and the Thurston Island area. A continued increase in the large‐scale advection of warm air from the midlatitudes toward the ASE could lead to an increased surface melting frequency with implications for ice shelves in the study area.

Weddell seal behaviour during an exceptional oceanographic event in the Filchner-Ronne Ice Shelf in 2017

AbstractRapid and regionally contrasting climate changes have been observed around Antarctica. However, our understanding of the impact of these changes on ecosystems remains limited, and there is an urgent need to better identify habitats of Antarctic species. The Weddell seal (Leptonychotes weddellii) is a circumpolar mesopredator and an indicative species of Antarctic marine communities. It has been extensively studied in the western Ross Sea and East Antarctica, and an understanding of its ecology in the Weddell Sea in the wintertime is emerging. We documented the behavioural response(s) of four Weddell seals from February to June in 2017 in the Filchner-Ronne Ice Shelf region and related these to unusual oceanographic conditions in 2017. Unexpectedly, we found that Weddell seals had the longest foraging effort within the outflow of Ice Shelf Water or at its turbulent boundary. They also foraged on the eastern side of the trough from April to June within the Modified Warm Deep Water and seem to take advantage of the unusual conditions of persistent inflow of warm waters through the winter. Linking animal behavioural responses to oceanographic conditions is informative for quantifying rarely recorded events and provides great insight into how predators may respond to changing conditions.

Ocean Access to Zachariæ Isstrøm Glacier, Northeast Greenland, Revealed by OMG Airborne Gravity

AbstractSeafloor topography shapes the pathways of ocean currents transporting ocean heat and, thus, is a fundamental boundary condition for modeling ocean‐ice interactions. However, few ship bathymetric data are available on the inner continental shelf of northeast Greenland due to the year‐round presence of sea ice. We infer seafloor topography of this region from airborne gravity anomaly measured by National Aeronautics and Space Administration's Oceans Melting Greenland (OMG) mission through a nonlinear inversion method called simulated annealing and results in a model with 1.95–3.9 km resolution and 52 m accuracy. The model provides a view of the seafloor near Zachariæ Isstrøm and reveals previously unknown topographic features such as a 370–560 m deep trough that enables warm subsurface water to reach Jøkelbugten fjord into which Zachariæ Isstrøm drains. Present bathymetric models do not show deep enough troughs near Jøkelbugten fjord allowing the inflow of warm water.

Strong ice-ocean interaction beneath Shirase Glacier Tongue in East Antarctica

Mass loss from the Antarctic ice sheet, Earth’s largest freshwater reservoir, results directly in global sea-level rise and Southern Ocean freshening. Observational and modeling studies have demonstrated that ice shelf basal melting, resulting from the inflow of warm water onto the Antarctic continental shelf, plays a key role in the ice sheet’s mass balance. In recent decades, warm ocean-cryosphere interaction in the Amundsen and Bellingshausen seas has received a great deal of attention. However, except for Totten Ice Shelf, East Antarctic ice shelves typically have cold ice cavities with low basal melt rates. Here we present direct observational evidence of high basal melt rates (7–16 m yr−1) beneath an East Antarctic ice shelf, Shirase Glacier Tongue, driven by southward-flowing warm water guided by a deep continuous trough extending to the continental slope. The strength of the alongshore wind controls the thickness of the inflowing warm water layer and the rate of basal melting.

Experimental and Model‐Based Investigation of the Effect of the Free‐Surface Flow Regime on the Detection Threshold of Warm Water Inflows

AbstractHeat has been used as a tracer to identify and quantify groundwater inflows into streams. Over the last decade, a few methods have used fiber‐optic distributed temperature sensing to facilitate assessment of such inflows into small streams. However, these methods focused mainly on the groundwater percentage and the thermal contrast between groundwater and surface water without considering the flow regime of the surface water. In this study, artificial water inflows into a controlled flume were examined using fiber‐optic distributed temperature sensing to quantify the thermal anomalies induced as a function of the flow regime (turbulent or laminar). Computer simulations were then performed to widen the range of the parameters tested and provide insight into the physical processes involved. Experiments conducted under the turbulent regime were in accordance with results and uncertainties of previous studies. Under the laminar regime, however, the inflow‐induced thermal anomalies were always smaller than those under the turbulent regime for a given inflow percentage. Therefore, the actual inflow percentage may be underestimated when using a classic method under a laminar regime.