Monthly Kachemak Bay Report, June 2026
Summary
After an unusually cold spring, deep waters continued to be colder than normal, continuing a marine cold spell that began in December 2025. Surface waters, however, had warmed up beyond the seasonal mean, resulting in a temperature difference of over 7 °C between surface and deep waters in the inner bay. Chlorophyll concentrations were still low, but not as low as in May. Unusually low oxygen saturation levels appear to be due to an instrument malfunction.
A complete set of up-to-date graphs can be found on this Google Drive: section plots and time sections (request access from martin.renner@noaa.gov).
Conditions
After a cold spring, temperatures were back to the seasonal mean in the weeks leading up to this June survey (Figure 1). After an unusually wet May, precipitation in June 2026 was close to the long-term mean (which is usually the driest time of the year). None of the SNOTEL stations around Kachemak Bay reported a remaining snowpack since mid-May.
The May 2026 Kasitsna Bay Lab oceanographic survey was conducted by Hans, Kris and Martin in calm conditions.
Physical oceanography
Temperature
Water temperatures during the June survey ranged from a minimum of 4.9 °C at station AlongBay-12 (69 m depth), in the inner bay, to a maximum of 12.7 °C at station AlongBay-11 (1 m depth) in the inner bay. Vertical stratification was pronounced in the inner bay, but was also evident in the outer bay, with a thin warm layer of fresher surface water layered over cooler, more saline mid/deep waters (Figure 2 (a), top-left panel). Mid- and deep outer bay waters tended to be warmer than inner bay waters, but no sharp horizontal front was observed.
June satellite sea surface temperature data showed that as inner Kachemak Bay, upper Cook Inlet was also warmer than the cooler waters of lower Cook Inlet and the Gulf of Alaska (Figure 3). A large pocked of cool water from lower Cook Inlet to east of Kodiak Island was surrounded by warmer waters.
Throughout the bay, deep waters were still cooler than normal (by up to one standard deviation). In contrast, the thin surface layer in the inner bay was not only up to 7 °C warmer than bottom waters, it had also warmed up to a remarkable two standard deviations above the long-term mean for this month (Figure 2 (a), top-right panel). The marine cold spell of early 2026 appeared to have therefore ended for surface waters of Kachemak Bay (Figure 5, Figure 4), but was lingering in deep waters at a reduced scale (Figure 6). Surface waters of the Gulf of Alaska and Bering Sea also remained colder than normal in June 2026, as shown by satellite data, in contrast to warmer than normal conditions across much of the North Pacific (Figure 7).
Salinity
Salinity values during the May survey ranged from 23.6 PSU at station AlongBay-13 (1m depth) in the inner bay to 31.5 PSU at station AlongBay-1 (56m depth) in the outer bay. A sharply demarcated layer of fresher water was present in the top 10-15 m in the inner and mid bay, and to a lesser degree in the outer bay (Figure 2). The layer of fresher water was thicker on the north than on the south side of the bay, indicative of the ant-clockwise current (Figure 2 (b)).Inner bay waters were fresher than outer bay waters at all depth, even though these differences were quite minor at depth (Figure 2 (a)).
Compared to the long-term means, most of Kachemak Bay was less saline than seasonally expected, reaching over 1.5 standard deviation in some places (Figure 2). This deviation was more pronounced in deep waters than in shallow waters, some of which showed slightly positive anomalies (Figure 2). Kachemak Bay has been fresher than normal for most of the past four years now (Figure 8, Figure 9).
Turbidity
Inner bay waters were more turbid than outer bay waters. Turbid waters extended from the inner bay into deep waters of the outer bay (Figure 2 (a)). Areas of higher surface turbidity were found in some areas of transient fresher surface water plumes, Compared to the seasonal mean, most waters were slightly less turbid than expected.
Biological conditions
Phytoplankton
Highest chlorophyll concentrations were found in outer bay at about 20 m depth (Figure 2 (a)). A subsurface band of elevated concentrations extended into the inner bay. Concentrations were below the seasonal mean in deep waters, but had areas above the expected mean in the active surface layer (Figure 2). Integrated over the entire water column, chlorophyll concentrations were higher than the extremely low concentrations in May, but remained low compared to the seasonal mean (Figure 10).
Oxygen
Inner bay and deep waters had lower oxygen saturations than outer bay and surface waters (Figure 2 (a)). Overall values were substantially lower than expected. The low values at the surface suggested that the instrument went out of calibration rather than an actual zone of depleted oxygen existing in the bay.
Wildlife
No marine mammals, other than sea otters were observed. Common murres and tufted puffins had returned in numbers to Gull Island and surrounding waters.
Mailing list
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