Large and transient positive temperature anomalies in Washington's coastal nearshore waters during the 2013-2015 northeast Pacific marine heatwave.

The northern portion of Washington's outer coast-known locally as the Olympic coast-is a dynamic region characterized by seasonal upwelling that predominates during summer interrupted by occasional periods of downwelling. We examined spring-to-fall water temperature records collected along this coast from 2001-2015 from April to October at four nearshore locations (Cape Elizabeth to Makah Bay) that span one degree of latitude and are located within 15 km of the shore. When compared against a long-term climatology created for 2001-2013, seven-day smoothed temperature anomalies of up to 4.5°C at 40 m depth during 2014 and 2015 show short-term warm events lasting 10-20 days. These periods of warming occurred within the well documented marine heatwave in the Northeast Pacific and were about twice the seasonal temperature range in the climatology at that depth. These warm events were strongly correlated with periods of northward long-shore winds and upper ocean currents, consistent with what is expected for the response to downwelling-favorable winds. While our focus a priori was on 2014 and 2015, we also found large positive temperature events in 2013, which were potentially related to the early stage of the marine heatwave, and in 2011, which did not have a documented marine heatwave. This indicates that near-shore short-term warm events occur during periods of large-scale offshore marine heatwave events, but also can occur in the absence of a large-scale marine heatwave event when downwelling-favorable winds occur during the summer/early fall.

Gender Equity in Oceanography.

Gender equity, providing for full participation of people of all genders in the oceanographic workforce, is an important goal for the continued success of the oceanographic enterprise. Here, we describe historical obstructions to gender equity; assess recent progress and the current status of gender equity in oceanography by examining quantitative measures of participation, achievement, and recognition; and review activities to improve gender equity. We find that women receive approximately half the oceanography PhDs in many parts of the world and are increasing in parity in earlier levels of academic employment. However, continued progress toward gender parity is needed, as reflected by metrics such as first-authored publications, funded grants, honors, and conference speaker invitations. Finally we make recommendations for the whole oceanographic community to continue to work together to create a culture where oceanographers of all genders can thrive, including eliminating harassment, reexamining selection and evaluation procedures, and removing structural inequities.

Threat by marine heatwaves to adaptive large marine ecosystems in an eddy-resolving model.

Marine heatwaves (MHWs), episodic periods of abnormally high sea surface temperature (SST), severely affect marine ecosystems. Large Marine Ecosystems (LMEs) cover ~22% of the global ocean but account for 95% of global fisheries catches. Yet how climate change affects MHWs over LMEs remains unknown, because such LMEs are confined to the coast where low-resolution climate models are known to have biases. Here, using a high-resolution Earth system model and applying a "future threshold" that considers MHWs as anomalous warming above the long-term mean warming of SSTs, we find that future intensity and annual days of MHWs over majority of the LMEs remain higher than in the present-day climate. Better resolution of ocean mesoscale eddies enables simulation of more realistic MHWs than low-resolution models. These increases in MHWs under global warming poses a serious threat to LMEs, even if resident organisms could adapt fully to the long-term mean warming.

Synoptic Mesoscale to Basin Scale Variability in Biological Productivity and Chlorophyll in the Kuroshio Extension Region.

The Kuroshio current separates from the Japanese coast to become the eastward flowing Kuroshio Extension (KE) characterized by a strong latitudinal density front, high levels of mesoscale (eddy) energy, and high chlorophyll a (Chl). While satellite measurements of Chl show evidence of the impact of mesoscale eddies on the standing stock of phytoplankton, there have been very limited synoptic, spatially resolved in situ estimates of productivity in this region. Here, we present underway measurements of oxygen/argon supersaturation (ΔO2/Ar), a tracer of net biological productivity, for the KE made in spring, summer, and early autumn. We find large seasonal differences in the relationships between ΔO2/Ar, Chl, and sea level anomaly (SLA), a proxy for local thermocline depth deviations driven by mesoscale eddies derived from satellite observations. We show that the KE is a pronounced hotspot of high ΔO2/Ar in spring, but corresponding surface Chl values are low and have no correlation with ΔO2/Ar. In summer, there is a hotspot of productivity associated with the Oyashio front, where ΔO2/Ar and Chl are strongly positively correlated. In autumn, ΔO2/Ar and Chl are consistently low throughout the region and also positively correlated. By combining our analysis of the in situ ΔO2/Ar data with complementary Argo, BGC-Argo, repeat hydrography, and SLA observations, we infer the combination of physical and biological controls that drive the observed distributions of ΔO2/Ar and Chl. We find that the KE and Oyashio currents both act to supply nutrients laterally, fueling regions of high productivity in spring and summer, respectively.

Sustained ocean changes contributed to sudden Antarctic sea ice retreat in late 2016.

After nearly three decades of observed increasing trends of Antarctic sea ice extent, in September-October-November 2016, there was a dramatic decrease. Here we document factors that contributed to that decrease. An atmosphere-only model with a specified positive convective heating anomaly in the eastern Indian/western Pacific Ocean, representing the record positive precipitation anomalies there in September-October-November 2016, produces an anomalous atmospheric Rossby wave response with mid- and high latitude surface wind anomalies that contribute to the decrease of Antarctic sea ice extent. The sustained decreases of Antarctic sea ice extent after late 2016 are associated with a warmer upper Southern Ocean. This is the culmination of a negative decadal trend of wind stress curl with positive Southern Annular Mode and negative Interdecadal Pacific Oscillation, Ekman suction that results in warmer water being moved upward in the column closer to the surface, a transition to positive Interdecadal Pacific Oscillation around 2014-2016, and negative Southern Annular Mode in late 2016.

Weather-Related Hazards and Population Change: A Study of Hurricanes and Tropical Storms in the United States, 1980-2012.

Environmental determinists predict that people move away from places experiencing frequent weather hazards, yet some of these areas have rapidly growing populations. This analysis examines the relationship between weather events and population change in all U.S. counties that experienced hurricanes and tropical storms between 1980 and 2012. Our database allows for more generalizable conclusions by accounting for heterogeneity in current and past hurricane events and losses and past population trends. We find that hurricanes and tropical storms affect future population growth only in counties with growing, high-density populations, which are only 2 percent of all counties. In those counties, current year hurricane events and related losses suppress future population growth, although cumulative hurricane-related losses actually elevate population growth. Low-density counties and counties with stable or declining populations experience no effect of these weather events. Our analysis provides a methodologically informed explanation for contradictory findings in prior studies.

Climate-forced variability of ocean hypoxia.

Oxygen (O(2)) is a critical constraint on marine ecosystems. As oceanic O(2) falls to hypoxic concentrations, habitability for aerobic organisms decreases rapidly. We show that the spatial extent of hypoxia is highly sensitive to small changes in the ocean's O(2) content, with maximum responses at suboxic concentrations where anaerobic metabolisms predominate. In model-based reconstructions of historical oxygen changes, the world's largest suboxic zone, in the Pacific Ocean, varies in size by a factor of 2. This is attributable to climate-driven changes in the depth of the tropical and subtropical thermocline that have multiplicative effects on respiration rates in low-O(2) water. The same mechanism yields even larger fluctuations in the rate of nitrogen removal by denitrification, creating a link between decadal climate oscillations and the nutrient limitation of marine photosynthesis.